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  • Ball to Ball Collision - Detection and Handling

    - by Simucal
    With the help of the Stack Overflow community I've written a pretty basic-but fun physics simulator. You click and drag the mouse to launch a ball. It will bounce around and eventually stop on the "floor". My next big feature I want to add in is ball to ball collision. The ball's movement is broken up into a x and y speed vector. I have gravity (small reduction of the y vector each step), I have friction (small reduction of both vectors each collision with a wall). The balls honestly move around in a surprisingly realistic way. I guess my question has two parts: What is the best method to detect ball to ball collision? Do I just have an O(n^2) loop that iterates over each ball and checks every other ball to see if it's radius overlaps? What equations do I use to handle the ball to ball collisions? Physics 101 How does it effect the two balls speed x/y vectors? What is the resulting direction the two balls head off in? How do I apply this to each ball? Handling the collision detection of the "walls" and the resulting vector changes were easy but I see more complications with ball-ball collisions. With walls I simply had to take the negative of the appropriate x or y vector and off it would go in the correct direction. With balls I don't think it is that way. Some quick clarifications: for simplicity I'm ok with a perfectly elastic collision for now, also all my balls have the same mass right now, but I might change that in the future. In case anyone is interested in playing with the simulator I have made so far, I've uploaded the source here (EDIT: Check the updated source below). Edit: Resources I have found useful 2d Ball physics with vectors: 2-Dimensional Collisions Without Trigonometry.pdf 2d Ball collision detection example: Adding Collision Detection Success! I have the ball collision detection and response working great! Relevant code: Collision Detection: for (int i = 0; i < ballCount; i++) { for (int j = i + 1; j < ballCount; j++) { if (balls[i].colliding(balls[j])) { balls[i].resolveCollision(balls[j]); } } } This will check for collisions between every ball but skip redundant checks (if you have to check if ball 1 collides with ball 2 then you don't need to check if ball 2 collides with ball 1. Also, it skips checking for collisions with itself). Then, in my ball class I have my colliding() and resolveCollision() methods: public boolean colliding(Ball ball) { float xd = position.getX() - ball.position.getX(); float yd = position.getY() - ball.position.getY(); float sumRadius = getRadius() + ball.getRadius(); float sqrRadius = sumRadius * sumRadius; float distSqr = (xd * xd) + (yd * yd); if (distSqr <= sqrRadius) { return true; } return false; } public void resolveCollision(Ball ball) { // get the mtd Vector2d delta = (position.subtract(ball.position)); float d = delta.getLength(); // minimum translation distance to push balls apart after intersecting Vector2d mtd = delta.multiply(((getRadius() + ball.getRadius())-d)/d); // resolve intersection -- // inverse mass quantities float im1 = 1 / getMass(); float im2 = 1 / ball.getMass(); // push-pull them apart based off their mass position = position.add(mtd.multiply(im1 / (im1 + im2))); ball.position = ball.position.subtract(mtd.multiply(im2 / (im1 + im2))); // impact speed Vector2d v = (this.velocity.subtract(ball.velocity)); float vn = v.dot(mtd.normalize()); // sphere intersecting but moving away from each other already if (vn > 0.0f) return; // collision impulse float i = (-(1.0f + Constants.restitution) * vn) / (im1 + im2); Vector2d impulse = mtd.multiply(i); // change in momentum this.velocity = this.velocity.add(impulse.multiply(im1)); ball.velocity = ball.velocity.subtract(impulse.multiply(im2)); } Source Code: Complete source for ball to ball collider. Binary: Compiled binary in case you just want to try bouncing some balls around. If anyone has some suggestions for how to improve this basic physics simulator let me know! One thing I have yet to add is angular momentum so the balls will roll more realistically. Any other suggestions? Leave a comment!

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  • Ball bouncing at a certain angle and efficiency computations

    - by X Y
    I would like to make a pong game with a small twist (for now). Every time the ball bounces off one of the paddles i want it to be under a certain angle (between a min and a max). I simply can't wrap my head around how to actually do it (i have some thoughts and such but i simply cannot implement them properly - i feel i'm overcomplicating things). Here's an image with a small explanation . One other problem would be that the conditions for bouncing have to be different for every edge. For example, in the picture, on the two small horizontal edges i do not want a perfectly vertical bounce when in the middle of the edge but rather a constant angle (pi/4 maybe) in either direction depending on the collision point (before the middle of the edge, or after). All of my collisions are done with the Separating Axes Theorem (and seem to work fine). I'm looking for something efficient because i want to add a lot of things later on (maybe polygons with many edges and such). So i need to keep to a minimum the amount of checking done every frame. The collision algorithm begins testing whenever the bounding boxes of the paddle and the ball intersect. Is there something better to test for possible collisions every frame? (more efficient in the long run,with many more objects etc, not necessarily easy to code). I'm going to post the code for my game: Paddle Class public class Paddle : Microsoft.Xna.Framework.DrawableGameComponent { #region Private Members private SpriteBatch spriteBatch; private ContentManager contentManager; private bool keybEnabled; private bool isLeftPaddle; private Texture2D paddleSprite; private Vector2 paddlePosition; private float paddleSpeedY; private Vector2 paddleScale = new Vector2(1f, 1f); private const float DEFAULT_Y_SPEED = 150; private Vector2[] Normals2Edges; private Vector2[] Vertices = new Vector2[4]; private List<Vector2> lst = new List<Vector2>(); private Vector2 Edge; #endregion #region Properties public float Speed { get {return paddleSpeedY; } set { paddleSpeedY = value; } } public Vector2[] Normal2EdgesVector { get { NormalsToEdges(this.isLeftPaddle); return Normals2Edges; } } public Vector2[] VertexVector { get { return Vertices; } } public Vector2 Scale { get { return paddleScale; } set { paddleScale = value; NormalsToEdges(this.isLeftPaddle); } } public float X { get { return paddlePosition.X; } set { paddlePosition.X = value; } } public float Y { get { return paddlePosition.Y; } set { paddlePosition.Y = value; } } public float Width { get { return (Scale.X == 1f ? (float)paddleSprite.Width : paddleSprite.Width * Scale.X); } } public float Height { get { return ( Scale.Y==1f ? (float)paddleSprite.Height : paddleSprite.Height*Scale.Y ); } } public Texture2D GetSprite { get { return paddleSprite; } } public Rectangle Boundary { get { return new Rectangle((int)paddlePosition.X, (int)paddlePosition.Y, (int)this.Width, (int)this.Height); } } public bool KeyboardEnabled { get { return keybEnabled; } } #endregion private void NormalsToEdges(bool isLeftPaddle) { Normals2Edges = null; Edge = Vector2.Zero; lst.Clear(); for (int i = 0; i < Vertices.Length; i++) { Edge = Vertices[i + 1 == Vertices.Length ? 0 : i + 1] - Vertices[i]; if (Edge != Vector2.Zero) { Edge.Normalize(); //outer normal to edge !! (origin in top-left) lst.Add(new Vector2(Edge.Y, -Edge.X)); } } Normals2Edges = lst.ToArray(); } public float[] ProjectPaddle(Vector2 axis) { if (Vertices.Length == 0 || axis == Vector2.Zero) return (new float[2] { 0, 0 }); float min, max; min = Vector2.Dot(axis, Vertices[0]); max = min; for (int i = 1; i < Vertices.Length; i++) { float p = Vector2.Dot(axis, Vertices[i]); if (p < min) min = p; else if (p > max) max = p; } return (new float[2] { min, max }); } public Paddle(Game game, bool isLeftPaddle, bool enableKeyboard = true) : base(game) { contentManager = new ContentManager(game.Services); keybEnabled = enableKeyboard; this.isLeftPaddle = isLeftPaddle; } public void setPosition(Vector2 newPos) { X = newPos.X; Y = newPos.Y; } public override void Initialize() { base.Initialize(); this.Speed = DEFAULT_Y_SPEED; X = 0; Y = 0; NormalsToEdges(this.isLeftPaddle); } protected override void LoadContent() { spriteBatch = new SpriteBatch(GraphicsDevice); paddleSprite = contentManager.Load<Texture2D>(@"Content\pongBar"); } public override void Update(GameTime gameTime) { //vertices array Vertices[0] = this.paddlePosition; Vertices[1] = this.paddlePosition + new Vector2(this.Width, 0); Vertices[2] = this.paddlePosition + new Vector2(this.Width, this.Height); Vertices[3] = this.paddlePosition + new Vector2(0, this.Height); // Move paddle, but don't allow movement off the screen if (KeyboardEnabled) { float moveDistance = Speed * (float)gameTime.ElapsedGameTime.TotalSeconds; KeyboardState newKeyState = Keyboard.GetState(); if (newKeyState.IsKeyDown(Keys.Down) && Y + paddleSprite.Height + moveDistance <= Game.GraphicsDevice.Viewport.Height) { Y += moveDistance; } else if (newKeyState.IsKeyDown(Keys.Up) && Y - moveDistance >= 0) { Y -= moveDistance; } } else { if (this.Y + this.Height > this.GraphicsDevice.Viewport.Height) { this.Y = this.Game.GraphicsDevice.Viewport.Height - this.Height - 1; } } base.Update(gameTime); } public override void Draw(GameTime gameTime) { spriteBatch.Begin(SpriteSortMode.Texture,null); spriteBatch.Draw(paddleSprite, paddlePosition, null, Color.White, 0f, Vector2.Zero, Scale, SpriteEffects.None, 0); spriteBatch.End(); base.Draw(gameTime); } } Ball Class public class Ball : Microsoft.Xna.Framework.DrawableGameComponent { #region Private Members private SpriteBatch spriteBatch; private ContentManager contentManager; private const float DEFAULT_SPEED = 50; private float speedIncrement = 0; private Vector2 ballScale = new Vector2(1f, 1f); private const float INCREASE_SPEED = 50; private Texture2D ballSprite; //initial texture private Vector2 ballPosition; //position private Vector2 centerOfBall; //center coords private Vector2 ballSpeed = new Vector2(DEFAULT_SPEED, DEFAULT_SPEED); //speed #endregion #region Properties public float DEFAULTSPEED { get { return DEFAULT_SPEED; } } public Vector2 ballCenter { get { return centerOfBall; } } public Vector2 Scale { get { return ballScale; } set { ballScale = value; } } public float SpeedX { get { return ballSpeed.X; } set { ballSpeed.X = value; } } public float SpeedY { get { return ballSpeed.Y; } set { ballSpeed.Y = value; } } public float X { get { return ballPosition.X; } set { ballPosition.X = value; } } public float Y { get { return ballPosition.Y; } set { ballPosition.Y = value; } } public Texture2D GetSprite { get { return ballSprite; } } public float Width { get { return (Scale.X == 1f ? (float)ballSprite.Width : ballSprite.Width * Scale.X); } } public float Height { get { return (Scale.Y == 1f ? (float)ballSprite.Height : ballSprite.Height * Scale.Y); } } public float SpeedIncreaseIncrement { get { return speedIncrement; } set { speedIncrement = value; } } public Rectangle Boundary { get { return new Rectangle((int)ballPosition.X, (int)ballPosition.Y, (int)this.Width, (int)this.Height); } } #endregion public Ball(Game game) : base(game) { contentManager = new ContentManager(game.Services); } public void Reset() { ballSpeed.X = DEFAULT_SPEED; ballSpeed.Y = DEFAULT_SPEED; ballPosition.X = Game.GraphicsDevice.Viewport.Width / 2 - ballSprite.Width / 2; ballPosition.Y = Game.GraphicsDevice.Viewport.Height / 2 - ballSprite.Height / 2; } public void SpeedUp() { if (ballSpeed.Y < 0) ballSpeed.Y -= (INCREASE_SPEED + speedIncrement); else ballSpeed.Y += (INCREASE_SPEED + speedIncrement); if (ballSpeed.X < 0) ballSpeed.X -= (INCREASE_SPEED + speedIncrement); else ballSpeed.X += (INCREASE_SPEED + speedIncrement); } public float[] ProjectBall(Vector2 axis) { if (axis == Vector2.Zero) return (new float[2] { 0, 0 }); float min, max; min = Vector2.Dot(axis, this.ballCenter) - this.Width/2; //center - radius max = min + this.Width; //center + radius return (new float[2] { min, max }); } public void ChangeHorzDirection() { ballSpeed.X *= -1; } public void ChangeVertDirection() { ballSpeed.Y *= -1; } public override void Initialize() { base.Initialize(); ballPosition.X = Game.GraphicsDevice.Viewport.Width / 2 - ballSprite.Width / 2; ballPosition.Y = Game.GraphicsDevice.Viewport.Height / 2 - ballSprite.Height / 2; } protected override void LoadContent() { spriteBatch = new SpriteBatch(GraphicsDevice); ballSprite = contentManager.Load<Texture2D>(@"Content\ball"); } public override void Update(GameTime gameTime) { if (this.Y < 1 || this.Y > GraphicsDevice.Viewport.Height - this.Height - 1) this.ChangeVertDirection(); centerOfBall = new Vector2(ballPosition.X + this.Width / 2, ballPosition.Y + this.Height / 2); base.Update(gameTime); } public override void Draw(GameTime gameTime) { spriteBatch.Begin(); spriteBatch.Draw(ballSprite, ballPosition, null, Color.White, 0f, Vector2.Zero, Scale, SpriteEffects.None, 0); spriteBatch.End(); base.Draw(gameTime); } } Main game class public class gameStart : Microsoft.Xna.Framework.Game { GraphicsDeviceManager graphics; SpriteBatch spriteBatch; public gameStart() { graphics = new GraphicsDeviceManager(this); Content.RootDirectory = "Content"; this.Window.Title = "Pong game"; } protected override void Initialize() { ball = new Ball(this); paddleLeft = new Paddle(this,true,false); paddleRight = new Paddle(this,false,true); Components.Add(ball); Components.Add(paddleLeft); Components.Add(paddleRight); this.Window.AllowUserResizing = false; this.IsMouseVisible = true; this.IsFixedTimeStep = false; this.isColliding = false; base.Initialize(); } #region MyPrivateStuff private Ball ball; private Paddle paddleLeft, paddleRight; private int[] bit = { -1, 1 }; private Random rnd = new Random(); private int updates = 0; enum nrPaddle { None, Left, Right }; private nrPaddle PongBar = nrPaddle.None; private ArrayList Axes = new ArrayList(); private Vector2 MTV; //minimum translation vector private bool isColliding; private float overlap; //smallest distance after projections private Vector2 overlapAxis; //axis of overlap #endregion protected override void LoadContent() { spriteBatch = new SpriteBatch(GraphicsDevice); paddleLeft.setPosition(new Vector2(0, this.GraphicsDevice.Viewport.Height / 2 - paddleLeft.Height / 2)); paddleRight.setPosition(new Vector2(this.GraphicsDevice.Viewport.Width - paddleRight.Width, this.GraphicsDevice.Viewport.Height / 2 - paddleRight.Height / 2)); paddleLeft.Scale = new Vector2(1f, 2f); //scale left paddle } private bool ShapesIntersect(Paddle paddle, Ball ball) { overlap = 1000000f; //large value overlapAxis = Vector2.Zero; MTV = Vector2.Zero; foreach (Vector2 ax in Axes) { float[] pad = paddle.ProjectPaddle(ax); //pad0 = min, pad1 = max float[] circle = ball.ProjectBall(ax); //circle0 = min, circle1 = max if (pad[1] <= circle[0] || circle[1] <= pad[0]) { return false; } if (pad[1] - circle[0] < circle[1] - pad[0]) { if (Math.Abs(overlap) > Math.Abs(-pad[1] + circle[0])) { overlap = -pad[1] + circle[0]; overlapAxis = ax; } } else { if (Math.Abs(overlap) > Math.Abs(circle[1] - pad[0])) { overlap = circle[1] - pad[0]; overlapAxis = ax; } } } if (overlapAxis != Vector2.Zero) { MTV = overlapAxis * overlap; } return true; } protected override void Update(GameTime gameTime) { updates += 1; float ftime = 5 * (float)gameTime.ElapsedGameTime.TotalSeconds; if (updates == 1) { isColliding = false; int Xrnd = bit[Convert.ToInt32(rnd.Next(0, 2))]; int Yrnd = bit[Convert.ToInt32(rnd.Next(0, 2))]; ball.SpeedX = Xrnd * ball.SpeedX; ball.SpeedY = Yrnd * ball.SpeedY; ball.X += ftime * ball.SpeedX; ball.Y += ftime * ball.SpeedY; } else { updates = 100; ball.X += ftime * ball.SpeedX; ball.Y += ftime * ball.SpeedY; } //autorun :) paddleLeft.Y = ball.Y; //collision detection PongBar = nrPaddle.None; if (ball.Boundary.Intersects(paddleLeft.Boundary)) { PongBar = nrPaddle.Left; if (!isColliding) { Axes.Clear(); Axes.AddRange(paddleLeft.Normal2EdgesVector); //axis from nearest vertex to ball's center Axes.Add(FORMULAS.NormAxisFromCircle2ClosestVertex(paddleLeft.VertexVector, ball.ballCenter)); } } else if (ball.Boundary.Intersects(paddleRight.Boundary)) { PongBar = nrPaddle.Right; if (!isColliding) { Axes.Clear(); Axes.AddRange(paddleRight.Normal2EdgesVector); //axis from nearest vertex to ball's center Axes.Add(FORMULAS.NormAxisFromCircle2ClosestVertex(paddleRight.VertexVector, ball.ballCenter)); } } if (PongBar != nrPaddle.None && !isColliding) switch (PongBar) { case nrPaddle.Left: if (ShapesIntersect(paddleLeft, ball)) { isColliding = true; if (MTV != Vector2.Zero) ball.X += MTV.X; ball.Y += MTV.Y; ball.ChangeHorzDirection(); } break; case nrPaddle.Right: if (ShapesIntersect(paddleRight, ball)) { isColliding = true; if (MTV != Vector2.Zero) ball.X += MTV.X; ball.Y += MTV.Y; ball.ChangeHorzDirection(); } break; default: break; } if (!ShapesIntersect(paddleRight, ball) && !ShapesIntersect(paddleLeft, ball)) isColliding = false; ball.X += ftime * ball.SpeedX; ball.Y += ftime * ball.SpeedY; //check ball movement if (ball.X > paddleRight.X + paddleRight.Width + 2) { //IncreaseScore(Left); ball.Reset(); updates = 0; return; } else if (ball.X < paddleLeft.X - 2) { //IncreaseScore(Right); ball.Reset(); updates = 0; return; } base.Update(gameTime); } protected override void Draw(GameTime gameTime) { GraphicsDevice.Clear(Color.Aquamarine); spriteBatch.Begin(SpriteSortMode.BackToFront, BlendState.AlphaBlend); spriteBatch.End(); base.Draw(gameTime); } } And one method i've used: public static Vector2 NormAxisFromCircle2ClosestVertex(Vector2[] vertices, Vector2 circle) { Vector2 temp = Vector2.Zero; if (vertices.Length > 0) { float dist = (circle.X - vertices[0].X) * (circle.X - vertices[0].X) + (circle.Y - vertices[0].Y) * (circle.Y - vertices[0].Y); for (int i = 1; i < vertices.Length;i++) { if (dist > (circle.X - vertices[i].X) * (circle.X - vertices[i].X) + (circle.Y - vertices[i].Y) * (circle.Y - vertices[i].Y)) { temp = vertices[i]; //memorize the closest vertex dist = (circle.X - vertices[i].X) * (circle.X - vertices[i].X) + (circle.Y - vertices[i].Y) * (circle.Y - vertices[i].Y); } } temp = circle - temp; temp.Normalize(); } return temp; } Thanks in advance for any tips on the 4 issues. EDIT1: Something isn't working properly. The collision axis doesn't come out right and the interpolation also seems to have no effect. I've changed the code a bit: private bool ShapesIntersect(Paddle paddle, Ball ball) { overlap = 1000000f; //large value overlapAxis = Vector2.Zero; MTV = Vector2.Zero; foreach (Vector2 ax in Axes) { float[] pad = paddle.ProjectPaddle(ax); //pad0 = min, pad1 = max float[] circle = ball.ProjectBall(ax); //circle0 = min, circle1 = max if (pad[1] < circle[0] || circle[1] < pad[0]) { return false; } if (Math.Abs(pad[1] - circle[0]) < Math.Abs(circle[1] - pad[0])) { if (Math.Abs(overlap) > Math.Abs(-pad[1] + circle[0])) { overlap = -pad[1] + circle[0]; overlapAxis = ax * (-1); } //to get the proper axis } else { if (Math.Abs(overlap) > Math.Abs(circle[1] - pad[0])) { overlap = circle[1] - pad[0]; overlapAxis = ax; } } } if (overlapAxis != Vector2.Zero) { MTV = overlapAxis * Math.Abs(overlap); } return true; } And part of the Update method: if (ShapesIntersect(paddleRight, ball)) { isColliding = true; if (MTV != Vector2.Zero) { ball.X += MTV.X; ball.Y += MTV.Y; } //test if (overlapAxis.X == 0) //collision with horizontal edge { } else if (overlapAxis.Y == 0) //collision with vertical edge { float factor = Math.Abs(ball.ballCenter.Y - paddleRight.Y) / paddleRight.Height; if (factor > 1) factor = 1f; if (overlapAxis.X < 0) //left edge? ball.Speed = ball.DEFAULTSPEED * Vector2.Normalize(Vector2.Reflect(ball.Speed, (Vector2.Lerp(new Vector2(-1, -3), new Vector2(-1, 3), factor)))); else //right edge? ball.Speed = ball.DEFAULTSPEED * Vector2.Normalize(Vector2.Reflect(ball.Speed, (Vector2.Lerp(new Vector2(1, -3), new Vector2(1, 3), factor)))); } else //vertex collision??? { ball.Speed = -ball.Speed; } } What seems to happen is that "overlapAxis" doesn't always return the right one. So instead of (-1,0) i get the (1,0) (this happened even before i multiplied with -1 there). Sometimes there isn't even a collision registered even though the ball passes through the paddle... The interpolation also seems to have no effect as the angles barely change (or the overlapAxis is almost never (-1,0) or (1,0) but something like (0.9783473, 0.02743843)... ). What am i missing here? :(

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  • Mass Ball-to-Ball Collision Handling (as in, lots of balls)

    - by BlueThen
    Update: Found out that I was using the radius as the diameter, which was why the mtd was overcompensating. Hi, StackOverflow. I've written a Processing program awhile back simulating ball physics. Basically, I have a large number of balls (1000), with gravity turned on. Detection works great, but my issue is that they start acting weird when they're bouncing against other balls in all directions. I'm pretty confident this involves the handling. For the most part, I'm using Jay Conrod's code. One part that's different is if (distance > 1.0) return; which I've changed to if (distance < 1.0) return; because the collision wasn't even being performed with the first bit of code, I'm guessing that's a typo. The balls overlap when I use his code, which isn't what I was looking for. My attempt to fix it was to move the balls to the edge of each other: float angle = atan2(y - collider.y, x - collider.x); float distance = dist(x,y, balls[ID2].x,balls[ID2].y); x = collider.x + radius * cos(angle); y = collider.y + radius * sin(angle); This isn't correct, I'm pretty sure of that. I tried the correction algorithm in the previous ball-to-ball topic: // get the mtd Vector2d delta = (position.subtract(ball.position)); float d = delta.getLength(); // minimum translation distance to push balls apart after intersecting Vector2d mtd = delta.multiply(((getRadius() + ball.getRadius())-d)/d); // resolve intersection -- // inverse mass quantities float im1 = 1 / getMass(); float im2 = 1 / ball.getMass(); // push-pull them apart based off their mass position = position.add(mtd.multiply(im1 / (im1 + im2))); ball.position = ball.position.subtract(mtd.multiply(im2 / (im1 + im2))); except my version doesn't use vectors, and every ball's weight is 1. The resulting code I get is this: PVector delta = new PVector(collider.x - x, collider.y - y); float d = delta.mag(); PVector mtd = new PVector(delta.x * ((radius + collider.radius - d) / d), delta.y * ((radius + collider.radius - d) / d)); // push-pull apart based on mass x -= mtd.x * 0.5; y -= mtd.y * 0.5; collider.x += mtd.x * 0.5; collider.y += mtd.y * 0.5; This code seems to over-correct collisions. Which doesn't make sense to me because in no other way do I modify the x and y values of each ball, other than this. Some other part of my code could be wrong, but I don't know. Here's the snippet of the entire ball-to-ball collision handling I'm using: if (alreadyCollided.contains(new Integer(ID2))) // if the ball has already collided with this, then we don't need to reperform the collision algorithm return; Ball collider = (Ball) objects.get(ID2); PVector collision = new PVector(x - collider.x, y - collider.y); float distance = collision.mag(); if (distance == 0) { collision = new PVector(1,0); distance = 1; } if (distance < 1) return; PVector velocity = new PVector(vx,vy); PVector velocity2 = new PVector(collider.vx, collider.vy); collision.div(distance); // normalize the distance float aci = velocity.dot(collision); float bci = velocity2.dot(collision); float acf = bci; float bcf = aci; vx += (acf - aci) * collision.x; vy += (acf - aci) * collision.y; collider.vx += (bcf - bci) * collision.x; collider.vy += (bcf - bci) * collision.y; alreadyCollided.add(new Integer(ID2)); collider.alreadyCollided.add(new Integer(ID)); PVector delta = new PVector(collider.x - x, collider.y - y); float d = delta.mag(); PVector mtd = new PVector(delta.x * ((radius + collider.radius - d) / d), delta.y * ((radius + collider.radius - d) / d)); // push-pull apart based on mass x -= mtd.x * 0.2; y -= mtd.y * 0.2; collider.x += mtd.x * 0.2; collider.y += mtd.y * 0.2; Thanks. (Apologies for lack of sources, stackoverflow thinks I'm a spammer)

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  • GUI device for throwing a ball

    - by Fredrik Johansson
    The hero has a ball, which shall be thrown with accuracy in a court on iPhone/iPad. The player is seen from above, in a 2D view. In game play, the player reach is between 1/15 and 1/6 of the height of the iPhone screen. The player will run, and try to outmaneuver his opponent, and then throw the ball at a specific location, which is guarded by the opponent (which is also shown on the screen). The player is controlled by a joystick, and that works ok, but how shall I control the stick? Maybe someone can propose a third control method? I've tried the following two approaches: Joystick: Hero has a reach of 1 meter, and this reach is marked with a semi-opaque circle around the player. The ball can be moved by a joystick. When the joystick is moved south, the ball is moved south within the reach circle. There is a direct coupling with the joystick and the position of the ball. I.e. when the joystick is moved max south, the ball is max south within the player reach. At each touch update the speed is calculated, and the Box2d ball position and ball speed are updated. NB, the ball will never be moved outside the reach as long as the player push the joystick. The ball is thrown by swiping the joystick to make the ball move, and then releasing the joystick. At release, the ball will get a smoothed speed of the joystick. Joystick Problem: The throwing accuracy gets bad, because the joystick can not be that big, and a small movement results in quite a large movement of the ball. If the user does not release before the end of the joystick maximum end point, the ball will stop, and when the user releases the joystick the speed of the ball will be zero. Bad... Touch pad A force is applied to the ball by a sweep on a touchpad. The ball is released when the sweep is ended, or when the ball is moved outside the player reach. As there is no one to one mapping between the swipe and the ball position, the precision can be improved. A large swipe can result in a small ball movement. Touch Pad Problem A touchpad is less intuitive. Users do not seem to know what to do with the touch pad. Some tap the touchpad, and then the ball just falls to the ground. As there is no one-to-one mapping, the ball can be moved outside the reach, and then it will just fall to the ground. It's a bit hard to control the ball, especially if the player also moves.

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  • 2D Ball Collisions with Corners

    - by Aaron
    I'm trying to write a 2D simulation of a ball that bounces off of fixed vertical and horizontal walls. Simulating collisions with the faces of the walls was pretty simple--just negate the X-velocity for a vertical wall or the Y-velocity for a horizontal wall. The problem is that the ball can also collide with the corners of the walls, where a horizontal wall meets with a vertical wall. I have already figured out how to detect when a collision with a corner is occurring. My question is how the ball should react to this collision--that is, how its X and Y velocities will change as a result. Here's a list of what I already know or know how to find: *The X and Y coordinates of the ball's center during the frame when a collision is detected *The X and Y components of the ball's velocity *The X and Y coordinates of the corner *The angle between the ball's center and the corner *The angle in which the ball is traveling just before the collision *The amount that the ball is overlapping the corner when the collision is detected I'm guessing that it's best to pretend that the corner is an infinitely small circle, so I can treat a collision between the ball and that circle as if the ball were colliding with a wall that runs tangent to the circles at the point of collision. It seems to me that all I need to do is rotate the coordinate system to line up with this imaginary wall, reverse the X component of the ball's velocity under this system, and rotate the coordinates back to the original system. The problem is that I have no idea how to program this. By the way, this is an ideal simulation. I'm not taking anything like friction or the ball's rotation into account. I'm using Objective-C, but I'd really just like a general algorithm or some advice. Many thanks if anyone can help!

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  • 1136: Incorrect number of arguments. Expected 0.? AS3 Flash Cs4

    - by charmaine
    Basically i am working through a book called..Foundation Actionscript 3.0 Animation, making things move. i am now on Chapter 9 - collision detection. On two lines of my code i get the 1135 error, letting me know that i have an incorrect number of arguments. Can anybody help me out on why this may be? package { import flash.display.Sprite; import flash.events.Event; public class Bubbles extends Sprite { private var balls:Array; private var numBalls:Number = 10; private var centerBall:Ball; private var bounce:Number = -1; private var spring:Number = 0.2; public function Bubbles() { init(); } private function init():void { balls = new Array(); centerBall = new Ball(100, 0xcccccc); addChild(centerBall); centerBall.x = stage.stageWidth / 2; centerBall.y = stage.stageHeight / 2; for(var i:uint = 0; i < numBalls; i++) { var ball:Ball = new Ball(Math.random() * 40 + 5, Math.random() * 0xffffff); ball.x = Math.random() * stage.stageWidth; ball.y = Math.random() * stage.stageHeight; ball.vx = Math.random() * 6 - 3; ball.vy = Math.random() * 6 - 3; addChild(ball); balls.push(ball); } addEventListener(Event.ENTER_FRAME, onEnterFrame); } private function onEnterFrame(event:Event):void { for(var i:uint = 0; i < numBalls; i++) { var ball:Ball = balls[i]; move(ball); var dx:Number = ball.x - centerBall.x; var dy:Number = ball.y - centerBall.y; var dist:Number = Math.sqrt(dx * dx + dy * dy); var minDist:Number = ball.radius + centerBall.radius; if(dist < minDist) { var angle:Number = Math.atan2(dy, dx); var tx:Number = centerBall.x + Math.cos(angle) * minDist; var ty:Number = centerBall.y + Math.sin(angle) * minDist; ball.vx += (tx - ball.x) * spring; ball.vy += (ty - ball.y) * spring; } } } ***private function move(ball:Ball):void*** { ball.x += ball.vx; ball.y += ball.vy; if(ball.x + ball.radius > stage.stageWidth) { ball.x = stage.stageWidth - ball.radius; ball.vx *= bounce; } else if(ball.x - ball.radius < 0) { ball.x = ball.radius; ball.vx *= bounce; } ***if(ball.y + ball.radius > stage.stageHeight)*** { ball.y = stage.stageHeight - ball.radius; ball.vy *= bounce; } else if(ball.y - ball.radius < 0) { ball.y = ball.radius; ball.vy *= bounce; } } } } The bold parts are the lines im having trouble with! please help..thanks in advance!!

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  • 1136: Incorrect number of arguments. Expected 0.? AS3 Flash Cs4 (Round 2)

    - by charmaine
    (I have asked this before but I dont think I was direct enough with my question and therefore it did not get resolved so here goes again!) I am working through a book called Foundation Actionscript 3.0 Animation, making things move. I am now on Chapter 9 - Collision Detection. On two lines of my code I get the 1135 error, letting me know that I have an incorrect number of arguments. I have highlighted the two areas in which this occurs with asterisks: package { import flash.display.Sprite; import flash.events.Event; public class Bubbles extends Sprite { private var balls:Array; private var numBalls:Number = 10; private var centerBall:Ball; private var bounce:Number = -1; private var spring:Number = 0.2; public function Bubbles() { init(); } private function init():void { balls = new Array(); ***centerBall = new Ball(100, 0xcccccc);*** addChild(centerBall); centerBall.x = stage.stageWidth / 2; centerBall.y = stage.stageHeight / 2; for(var i:uint = 0; i < numBalls; i++) { ***var ball:Ball = new Ball(Math.random() * 40 + 5, Math.random() * 0xffffff);*** ball.x = Math.random() * stage.stageWidth; ball.y = Math.random() * stage.stageHeight; ball.vx = Math.random() * 6 - 3; ball.vy = Math.random() * 6 - 3; addChild(ball); balls.push(ball); } addEventListener(Event.ENTER_FRAME, onEnterFrame); } private function onEnterFrame(event:Event):void { for(var i:uint = 0; i < numBalls; i++) { var ball:Ball = balls[i]; move(ball); var dx:Number = ball.x - centerBall.x; var dy:Number = ball.y - centerBall.y; var dist:Number = Math.sqrt(dx * dx + dy * dy); var minDist:Number = ball.radius + centerBall.radius; if(dist < minDist) { var angle:Number = Math.atan2(dy, dx); var tx:Number = centerBall.x + Math.cos(angle) * minDist; var ty:Number = centerBall.y + Math.sin(angle) * minDist; ball.vx += (tx - ball.x) * spring; ball.vy += (ty - ball.y) * spring; } } } private function move(ball:Ball):void { ball.x += ball.vx; ball.y += ball.vy; if(ball.x + ball.radius > stage.stageWidth) { ball.x = stage.stageWidth - ball.radius; ball.vx *= bounce; } else if(ball.x - ball.radius < 0) { ball.x = ball.radius; ball.vx *= bounce; } if(ball.y + ball.radius > stage.stageHeight) { ball.y = stage.stageHeight - ball.radius; ball.vy *= bounce; } else if(ball.y - ball.radius < 0) { ball.y = ball.radius; ball.vy *= bounce; } } } } I think this is due to the non-existance of a Ball.as, when reading the tutorial I assumed it meant that I had to create a movie clip of a ball on stage and then export it for actionscript with the class name being Ball, however when flicking back through the book I saw that a Ball.as already existed, stating that I may need to use this again later on in the book, this read: package { import flash.display.Sprite; public class Ball extends Sprite { private var radius:Number; private var color:uint; public var vx:Number=0; public var vy:Number=0; public function Ball(radius:Number=40, color:uint=0xff0000) { this.radius=radius; this.color=color; init(); } public function init():void { graphics.beginFill(color); graphics.drawCircle(0, 0, radius); graphics.endFill(); } } } This managed to stop all the errors appearing however, it did not transmit any of the effects from Bubbles.as it just braught a Red Ball on the center of the stage. How would I alter this code in order to work in favour of Bubbles.as? Please Help! Thanks!

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  • Are there any ball tracking algorithms/patterns around in game programming

    - by user214626
    Hello, I am a newbie to game programming,I would need the suggestions and help of the wonderful people around here. I have set of players, and a ball, the players can kick the ball around the ground (not yet a football game, neither a foosball game too ).Are there any algorithms/ patterns for addressing the problems with tracking the ball and taking decisions, Is that too much to ask.What I was looking at is something like a collision detection algorithm for the common problem of 2 objects interacting with one another.

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  • XNA C# Rectangle Intersect Ball on a Square

    - by user2436057
    I made a Game like Peggle Deluxe using C# and XNA for lerning. I have 2 rectangles a ball and a square field. The ball gets shoot out with a cannon and if the Ball hits the Square the Square disapears and the Ball flys away.But the Ball doesent spring of realistically, it sometimes flys away in a different direction or gets stuck on the edge. Thads my Code at the moment: public void Update(Ball b, Deadline dl) { ArrayList listToDelete = new ArrayList(); foreach (Field aField in allFields) { if (aField.square.Intersects(b.ballhere)) { listToDelete.Add(aField); Punkte = Punkte + 100; float distanceX = Math.Abs(b.ballhere.X - aField.square.X); float distanceY = Math.Abs(b.ballhere.Y - aField.square.Y); if (distanceX < distanceY) { b.myMovement.X = -b.myMovement.X; } else { b.myMovement.Y = -b.myMovement.Y; } } } It changes the X or Y axis depending on how the ball hits the Square but not everytimes. What could cause the problem? Thanks for your answer. Greetings from Switzerland.

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  • Detecting collision between ball (circle) and brick(rectangle)?

    - by James Harrison
    Ok so this is for a small uni project. My lecturer provided me with a framework for a simple brickbreaker game. I am currently trying to overcome to problem of detecting a collision between the two game objects. One object is always the ball and the other objects can either be the bricks or the bat. public Collision hitBy( GameObject obj ) { //obj is the bat or the bricks //the current object is the ball // if ball hits top of object if(topX + width >= obj.topX && topX <= obj.topX + obj.width && topY + height >= obj.topY - 2 && topY + height <= obj.topY){ return Collision.HITY; } //if ball hits left hand side else if(topY + height >= obj.topY && topY <= obj.topY + obj.height && topX + width >= obj.topX -2 && topX + width <= obj.topX){ return Collision.HITX; } else return Collision.NO_HIT; } So far I have a method that is used to detect this collision. The the current obj is a ball and the obj passed into the method is the the bricks. At the moment I have only added statement to check for left and top collisions but do not want to continue as I have a few problems. The ball reacts perfectly if it hits the top of the bricks or bat but when it hits the ball often does not change directing. It seems that it is happening toward the top of the left hand edge but I cannot figure out why. I would like to know if there is another way of approaching this or if people know where I'm going wrong. Lastly the collision.HITX calls another method later on the changes the x direction likewise with y.

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  • Multiple setInterval in a HTML5 Canvas game

    - by kushsolitary
    I'm trying to achieve multiple animations in a game that I am creating using Canvas (it is a simple ping-pong game). This is my first game and I am new to canvas but have created a few experiments before so I have a good knowledge about how canvas work. First, take a look at the game here. The problem is, when the ball hits the paddle, I want a burst of n particles at the point of contact but that doesn't came right. Even if I set the particles number to 1, they just keep coming from the point of contact and then hides automatically after some time. Also, I want to have the burst on every collision but it occurs on first collision only. I am pasting the code here: //Initialize canvas var canvas = document.getElementById("canvas"), ctx = canvas.getContext("2d"), W = window.innerWidth, H = window.innerHeight, particles = [], ball = {}, paddles = [2], mouse = {}, points = 0, fps = 60, particlesCount = 50, flag = 0, particlePos = {}; canvas.addEventListener("mousemove", trackPosition, true); //Set it's height and width to full screen canvas.width = W; canvas.height = H; //Function to paint canvas function paintCanvas() { ctx.globalCompositeOperation = "source-over"; ctx.fillStyle = "black"; ctx.fillRect(0, 0, W, H); } //Create two paddles function createPaddle(pos) { //Height and width this.h = 10; this.w = 100; this.x = W/2 - this.w/2; this.y = (pos == "top") ? 0 : H - this.h; } //Push two paddles into the paddles array paddles.push(new createPaddle("bottom")); paddles.push(new createPaddle("top")); //Setting up the parameters of ball ball = { x: 2, y: 2, r: 5, c: "white", vx: 4, vy: 8, draw: function() { ctx.beginPath(); ctx.fillStyle = this.c; ctx.arc(this.x, this.y, this.r, 0, Math.PI*2, false); ctx.fill(); } }; //Function for creating particles function createParticles(x, y) { this.x = x || 0; this.y = y || 0; this.radius = 0.8; this.vx = -1.5 + Math.random()*3; this.vy = -1.5 + Math.random()*3; } //Draw everything on canvas function draw() { paintCanvas(); for(var i = 0; i < paddles.length; i++) { p = paddles[i]; ctx.fillStyle = "white"; ctx.fillRect(p.x, p.y, p.w, p.h); } ball.draw(); update(); } //Mouse Position track function trackPosition(e) { mouse.x = e.pageX; mouse.y = e.pageY; } //function to increase speed after every 5 points function increaseSpd() { if(points % 4 == 0) { ball.vx += (ball.vx < 0) ? -1 : 1; ball.vy += (ball.vy < 0) ? -2 : 2; } } //function to update positions function update() { //Move the paddles on mouse move if(mouse.x && mouse.y) { for(var i = 1; i < paddles.length; i++) { p = paddles[i]; p.x = mouse.x - p.w/2; } } //Move the ball ball.x += ball.vx; ball.y += ball.vy; //Collision with paddles p1 = paddles[1]; p2 = paddles[2]; if(ball.y >= p1.y - p1.h) { if(ball.x >= p1.x && ball.x <= (p1.x - 2) + (p1.w + 2)){ ball.vy = -ball.vy; points++; increaseSpd(); particlePos.x = ball.x, particlePos.y = ball.y; flag = 1; } } else if(ball.y <= p2.y + 2*p2.h) { if(ball.x >= p2.x && ball.x <= (p2.x - 2) + (p2.w + 2)){ ball.vy = -ball.vy; points++; increaseSpd(); particlePos.x = ball.x, particlePos.y = ball.y; flag = 1; } } //Collide with walls if(ball.x >= W || ball.x <= 0) ball.vx = -ball.vx; if(ball.y > H || ball.y < 0) { clearInterval(int); } if(flag == 1) { setInterval(emitParticles(particlePos.x, particlePos.y), 1000/fps); } } function emitParticles(x, y) { for(var k = 0; k < particlesCount; k++) { particles.push(new createParticles(x, y)); } counter = particles.length; for(var j = 0; j < particles.length; j++) { par = particles[j]; ctx.beginPath(); ctx.fillStyle = "white"; ctx.arc(par.x, par.y, par.radius, 0, Math.PI*2, false); ctx.fill(); par.x += par.vx; par.y += par.vy; par.radius -= 0.02; if(par.radius < 0) { counter--; if(counter < 0) particles = []; } } } var int = setInterval(draw, 1000/fps); Now, my function for emitting particles is on line 156, and I have called this function on line 151. The problem here can be because of I am not resetting the flag variable but I tried doing that and got more weird results. You can check that out here. By resetting the flag variable, the problem of infinite particles gets resolved but now they only animate and appear when the ball collides with the paddles. So, I am now out of any solution.

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  • Java Spotlight Episode 99: Daniel Blaukopf on JavaFX for Embedded Systems

    - by Roger Brinkley
    Interview with  Daniel Blaukopf on JavaFX for Embedded Systems Right-click or Control-click to download this MP3 file. You can also subscribe to the Java Spotlight Podcast Feed to get the latest podcast automatically. If you use iTunes you can open iTunes and subscribe with this link:  Java Spotlight Podcast in iTunes. Show Notes News Top 5 Reasons to go to JavaOne 5. Chance to see the future of Java Technical Keynotes and sessions The pavillion The new [email protected] conference 4. The meetings outside the scope of the conference Top 10 Reasons to Attend the Oracle Appreciation Event GlassFish Community Event at JavaOne 2012 Sundays User Group Forum 3. It’s like drinking from firehose Less keynotes more sessions - 20% more 60% of the talks are external to HOLs Tutorials OracleJava University classes on Sunday - Top Five Reasons You Should Attend Java University at JavaOne 2. Students are free 1. It’s not what you see it’s who you will meet Events Sep 10-15, IMTS 2012 Conference,  Chicago Sep 12,  The Coming M2M Revolution: Critical Issues for End-to-End Software and Systems Development,  Webinar Sep 30-Oct 4, JavaONE, San Francisco Oct 3-4, Java Embedded @ JavaONE, San Francisco Oct 15-17, JAX London Oct 30-Nov 1, Arm TechCon, Santa Clara Oct 22-23, Freescale Technology Forum - Japan, Tokyo Oct 31, JFall, Netherlands Nov 2-3, JMagreb, Morocco Nov 13-17, Devoxx, Belgium Feature InterviewDaniel Blaukopf is the Embedded Java Client Architect at Oracle, working on JavaFX. Daniel's focus in his 14 years in the Java organization has been mobile and embedded devices, including working with device manufacturers to port and tune all levels of the Java stack to their hardware and software environments. Daniel's particular interests are: graphics, performance optimization and functional programming.

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  • How display path ball will bounce?

    - by boolean
    I'm trying to figure out a way to show the path a ball will travel, so that the player can line up a shot before they fire the ball. I can't think of a way to calculate this path in advance and show it to the player, especially if it involves collision detection. At first I thought I would run the game at a super high speed for one update, plot the path with some dotted lines where the ball bounced, and then in the next frame hide the 'tracer' ball. This seems to have two issues - Calculating collision detection without actually updating the frames and collision detection getting less reliable at high speeds. If they were straight lines I think I could figure this out in a while loop, but trying to take into account the speed of the ball, the curve of the path, the reflecting from other objects..it all seems a bit much. I'm not looking for any code and this isn't a platform specific question, more just help trying to figure out conceptually how this would work. Can this be done? Are there techniques to achieve this?

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  • Collisions between moving ball and polygons

    - by miguelSantirso
    I know this is a very typical problem and that there area a lot of similar questions, but I have been looking for a while and I have not found anything that fits what I want. I am developing a 2D game in which I need to perform collisions between a ball and simple polygons. The polygons are defined as an array of vertices. I have implemented the collisions with the bounding boxes of the polygons (that was easy) and I need to refine that collision in the cases where the ball collides with the bounding box. The ball can move quite fast and the polygons are not too big so I need to perform continuous collisions. I am looking for a method that allows me to detect if the ball collides with a polygon and, at the same time, calculate the new direction for the ball after bouncing in the polygon. (I am using XNA, in case that helps)

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  • Bouncing ball slowing down over time

    - by user46610
    I use the unreal engine 4 to bounce a ball off of walls in a 2D space, but over time the ball gets slower and slower. Movement happens in the tick function of the ball FVector location = GetActorLocation(); location.X += this->Velocity.X * DeltaSeconds; location.Y += this->Velocity.Y * DeltaSeconds; SetActorLocation(location, true); When a wall gets hit I get a Hit Event with the normal of the collision. This is how I calculate the new velocity of the ball: FVector2D V = this->Velocity; FVector2D N = FVector2D(HitNormal.X, HitNormal.Y); FVector2D newVelocity = -2 * (V.X * N.X + V.Y * N.Y) * N + V; this->Velocity = newVelocity; Over time, the more the ball bounced around, the velocity gets smaller and smaller. How do I prevent speed loss when bouncing off walls like that? It's supposed to be a perfect bounce without friction or anything.

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  • accessing object variables in javascript

    - by user1452370
    So, I just started javascript and everything was working fine till i came to objects. This peace of code is supposed to create a bouncing ball in a html canvas with javascript but it doesn't work. var canvas = document.getElementById("myCanvas"); var ctx = canvas.getContext("2d"); //clear function clear() { ctx.clearRect(0, 0, canvas.width, canvas.height); } here is my ball object //ball var ball = { x: canvas.width / 2, getX: function() { return x; }, setX: function(a) { x = a; }, y: canvas.height / 2, getY: function() { return y; }, setY: function(a) { y = a; }, mx: 2, getMx: function() { return mx; }, my: 4, getMy: function() { return my; }, r: 10, getR: function() { return r; } }; code to draw my ball function drawBall() { ctx.beginPath(); ctx.arc(ball.getX, ball.getY, ball.getR, 0, Math.PI * 2, true); ctx.fillStyle = "#83F52C"; ctx.fill(); } function circle(x, y, r) { ctx.beginPath(); ctx.arc(x, y, r, 0, Math.PI * 2, true); ctx.fillStyle = "#83F52C"; ctx.fill(); } //draws ball and updates x,y cords function draw() { clear(); drawBall(); if (ball.getX() + ball.getMx() >= canvas.width || ball.getX()+ ball.getMx() <= 0) { ball.setMx(-ball.getMx()); } if (ball.getY() + ball.getMy() >= canvas.height|| ball.getY()+ ball.getMy() <= 0) { ball.setMy(-ball.getMy()); } ball.setX(ball.getX() + ball.getMx()); ball.setY(ball.getY() + ball.getMy()); } set interval function init() { return setInterval(draw, 10); } init();

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  • 2D Gaming - How to reflect a ball off the bat?

    - by sid
    Hi there I am pretty new to XNA & game dev and am stuck at ball reflection. My ball is reflecting once it hits the bat, but only in one angle, no matter which angle the bat is at. Here's the code: if (BallRect.Intersects(BatRect)) { Vector2 NormBallVelocity = Ball.velocity; NormBallVelocity.Normalize(); NormBallVelocity = Vector2.Reflect(Ball.velocity, NormBallVelocity); Ball.velocity = NormBallVelocity; } The ball is retracting its way back. How do I make it look like the ball is reflecting off the bat? I have seen other posts but they are on 3D front I am too new to translate it to 2D terms... Thanks Sid

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  • Keep Your Eye on the Ball

    - by [email protected]
    With the FIFA World Cup 2010 in South Africa almost a week underway, the soccer fans all around the World are talking about at least 2 things. That typical vuvuzela sound and the new Jabulani ball, saying it moves unpredictably, is difficult to handle and somehow the altitude of the World Cup stadiums also seem to be a contributing factor.(Picture taken from http://www.flickr.com/photos/warrenski/4143923059/ under a Creative Commons license)Although the FIFA states that it hasn't received any official complaints, the end users don't seem to be very happy with this new ball. This brings me to a comparison with IT management and testing. When you're in a situation where you're introducing a new product, in IT terms, introducing a new application, you would like to test all possible scenarios that your end users could be using and experiencing. However, that's a very time and resource intensive process to do for every application change or update.  It's like getting ready for the big game but you have no game plan.That's why a new approach has been developed. One that's based on the 80/20 rule. Testing 80% of the application will cost about 20% of the efforts. The remaining 20% of your application will not be tested before deployment, but monitored with a real user monitoring solution immediately after deployment. These tools track all user experiences, including error messages and the performance and availability metrics from an end user perspective. Should any anomaly occur, you would be able to repair it quickly so you and your end users can get back into the game.These real user sessions can be easily converted into testing scripts, so the 80% of the application testing can be complimented with the remaining 20%.Oracle Enterprise Manager 11g group of products offers both the real user monitoring solution with Oracle Real User Experience Insight, as well as the required testing solution with Oracle Application Testing Suite. Visit our Oracle Enterprise Manager 11g resource center and find out how it's Business-Driven IT Management approach will help you keep your eye on your business ball.Happy World Cup.

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  • Le C en 20 heures d'Eric Berthomier et Daniel Schang

    Nous avons le plaisir de vous présenter le livre "Le C en 20 heures" d'Eric Berthomier et Daniel Schang à consulter ou à télécharger gratuitement. Citation: L'ouvrage que vous tenez dans les mains ou que vous consultez sur votre écran a pour objectif de vous faire découvrir, par la pratique, la programmation en langage C. Il a été testé par de nombreux étudiants qui n'avaient aucune connaissance préalable de ce langage. En 20 à 30 heures de ...

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  • Bouncing ball isssue

    - by user
    I am currently working on the 2D Bouncing ball physics that bounces the ball up and down. The physics behaviour works fine but at the end the velocity keep +3 then 0 non-stop even the ball has stopped bouncing. How should I modify the code to fix this issue? ballPos = D3DXVECTOR2( 50, 100 ); velocity = 0; accelaration = 3.0f; isBallUp = false; void GameClass::Update() { velocity += accelaration; ballPos.y += velocity; if ( ballPos.y >= 590 ) isBallUp = true; else isBallUp = false; if ( isBallUp ) { ballPos.y = 590; velocity *= -1; } // Graphics Rendering m_Graphics.BeginFrame(); ComposeFrame(); m_Graphics.EndFrame(); }

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  • How to give a ball a following texture trailing effect

    - by Evan Kohilas
    How do I draw copies of the leading texture so that there is a line of the leading ball following behind it? (that don't collide) So far I have tried to create the effect by placing another graphic 2 pixels off the graphic, but I don't see the second ball being drawn. spriteBatch.Draw(ballTexture, ballPos, null, Color.White, 0.0f, new Vector2(Ballpos.X +2, ballPos.Y +2), ballSize, SpriteEffects.None, 0); Thanks.

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  • Critical Patch Update For Oracle Fusion Middleware – CPU October 2012 by Daniel Mortimer

    - by JuergenKress
    The latest Critical Patch Update (CPU) has been released for Oracle products. Start your reading here. Patch Set Update and Critical Patch Update October 2012 Availability Document [ID 1477727.1] Oracle Fusion Middleware 11g Release 2 11.1.2.0 Oracle Fusion Middleware 11g Release 1 11.1.1.4 (Portal,Forms,Reports and Discoverer) 11.1.1.5 11.1.1.6 Oracle Application Server 10g Release 3 10.1.3.5 Read the full article here. WebLogic Partner Community For regular information become a member in the WebLogic Partner Community please visit: http://www.oracle.com/partners/goto/wls-emea ( OPN account required). If you need support with your account please contact the Oracle Partner Business Center. BlogTwitterLinkedInMixForumWiki Technorati Tags: patch ofm,critical patch,WebLogic Community,Oracle,OPN,Jürgen Kress

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  • 2D Platformer Collision Handling

    - by defender-zone
    Hello, everyone! I am trying to create a 2D platformer (Mario-type) game and I am some having some issues with handling collisions properly. I am writing this game in C++, using SDL for input, image loading, font loading, etcetera. I am also using OpenGL via the FreeGLUT library in conjunction with SDL to display graphics. My method of collision detection is AABB (Axis-Aligned Bounding Box), which is really all I need to start with. What I need is an easy way to both detect which side the collision occurred on and handle the collisions properly. So, basically, if the player collides with the top of the platform, reposition him to the top; if there is a collision to the sides, reposition the player back to the side of the object; if there is a collision to the bottom, reposition the player under the platform. I have tried many different ways of doing this, such as trying to find the penetration depth and repositioning the player backwards by the penetration depth. Sadly, nothing I've tried seems to work correctly. Player movement ends up being very glitchy and repositions the player when I don't want it to. Part of the reason is probably because I feel like this is something so simple but I'm over-thinking it. If anyone thinks they can help, please take a look at the code below and help me try to improve on this if you can. I would like to refrain from using a library to handle this (as I want to learn on my own) or the something like the SAT (Separating Axis Theorem) if at all possible. Thank you in advance for your help! void world1Level1CollisionDetection() { for(int i; i < blocks; i++) { if (de2dCheckCollision(ball,block[i],0.0f,0.0f)==true) { int up = 0; int left = 0; int right = 0; int down = 0; if(ball.coords[0] < block[i].coords[0] && block[i].coords[0] < ball.coords[2] && ball.coords[2] < block[i].coords[2]) { left = 1; } if(block[i].coords[0] < ball.coords[0] && ball.coords[0] < block[i].coords[2] && block[i].coords[2] < ball.coords[2]) { right = 1; } if(ball.coords[1] < block[i].coords[1] && block[i].coords[1] < ball.coords[3] && ball.coords[3] < block[i].coords[3]) { up = 1; } if(block[i].coords[1] < ball.coords[1] && ball.coords[1] < block[i].coords[3] && block[i].coords[3] < ball.coords[3]) { down = 1; } cout << left << ", " << right << ", " << up << ", " << down << ", " << endl; if (left == 1) { ball.coords[0] = block[i].coords[0] - 16.0f; ball.coords[2] = block[i].coords[0] - 0.0f; } if (right == 1) { ball.coords[0] = block[i].coords[2] + 0.0f; ball.coords[2] = block[i].coords[2] + 16.0f; } if (down == 1) { ball.coords[1] = block[i].coords[3] + 0.0f; ball.coords[3] = block[i].coords[3] + 16.0f; } if (up == 1) { ball.yspeed = 0.0f; ball.gravity = 0.0f; ball.coords[1] = block[i].coords[1] - 16.0f; ball.coords[3] = block[i].coords[1] - 0.0f; } } if (de2dCheckCollision(ball,block[i],0.0f,0.0f)==false) { ball.gravity = -0.5f; } } } To explain what some of this code means: The blocks variable is basically an integer that is storing the amount of blocks, or platforms. I am checking all of the blocks using a for loop, and the number that the loop is currently on is represented by integer i. The coordinate system might seem a little weird, so that's worth explaining. coords[0] represents the x position (left) of the object (where it starts on the x axis). coords[1] represents the y position (top) of the object (where it starts on the y axis). coords[2] represents the width of the object plus coords[0] (right). coords[3] represents the height of the object plus coords[1] (bottom). de2dCheckCollision performs an AABB collision detection. Up is negative y and down is positive y, as it is in most games. Hopefully I have provided enough information for someone to help me successfully. If there is something I left out that might be crucial, let me know and I'll provide the necessary information. Finally, for anyone who can help, providing code would be very helpful and much appreciated. Thank you again for your help!

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  • 3D Ball Physics Theory: collision response on ground and against walls?

    - by David
    I'm really struggling to get a strong grasp on how I should be handling collision response in a game engine I'm building around a 3D ball physics concept. Think Monkey Ball as an example of the type of gameplay. I am currently using sphere-to-sphere broad phase, then AABB to OBB testing (the final test I am using right now is one that checks if one of the 8 OBB points crosses the planes of the object it is testing against). This seems to work pretty well, and I am getting back: Plane that object is colliding against (with a point on the plane, the plane's normal, and the exact point of intersection. I've tried what feels like dozens of different high-level strategies for handling these collisions, without any real success. I think my biggest problem is understanding how to handle collisions against walls in the x-y axes (left/right, front/back), which I want to have elasticity, and the ground (z-axis) where I want an elastic reaction if the ball drops down, but then for it to eventually normalize and be kept "on the ground" (not go into the ground, but also not continue bouncing). Without kluging something together, I'm positive there is a good way to handle this, my theories just aren't getting me all the way there. For physics modeling and movement, I am trying to use a Euler based setup with each object maintaining a position (and destination position prior to collision detection), a velocity (which is added onto the position to determine the destination position), and an acceleration (which I use to store any player input being put on the ball, as well as gravity in the z coord). Starting from when I detect a collision, what is a good way to approach the response to get the expected behavior in all cases? Thanks in advance to anyone taking the time to assist... I am grateful for any pointers, and happy to post any additional info or code if it is useful. UPDATE Based on Steve H's and eBusiness' responses below, I have adapted my collision response to what makes a lot more sense now. It was close to right before, but I didn't have all the right pieces together at the right time! I have one problem left to solve, and that is what is causing the floor collision to hit every frame. Here's the collision response code I have now for the ball, then I'll describe the last bit I'm still struggling to understand. // if we are moving in the direction of the plane (against the normal)... if (m_velocity.dot(intersection.plane.normal) <= 0.0f) { float dampeningForce = 1.8f; // eventually create this value based on mass and acceleration // Calculate the projection velocity PVRTVec3 actingVelocity = m_velocity.project(intersection.plane.normal); m_velocity -= actingVelocity * dampeningForce; } // Clamp z-velocity to zero if we are within a certain threshold // -- NOTE: this was an experimental idea I had to solve the "jitter" bug I'll describe below float diff = 0.2f - abs(m_velocity.z); if (diff > 0.0f && diff <= 0.2f) { m_velocity.z = 0.0f; } // Take this object to its new destination position based on... // -- our pre-collision position + vector to the collision point + our new velocity after collision * time // -- remaining after the collision to finish the movement m_destPosition = m_position + intersection.diff + (m_velocity * intersection.tRemaining * GAMESTATE->dt); The above snippet is run after a collision is detected on the ball (collider) with a collidee (floor in this case). With a dampening force of 1.8f, the ball's reflected "upward" velocity will eventually be overcome by gravity, so the ball will essentially be stuck on the floor. THIS is the problem I have now... the collision code is running every frame (since the ball's z-velocity is constantly pushing it a collision with the floor below it). The ball is not technically stuck, I can move it around still, but the movement is really goofy because the velocity and position keep getting affected adversely by the above snippet. I was experimenting with an idea to clamp the z-velocity to zero if it was "close to zero", but this didn't do what I think... probably because the very next frame the ball gets a new gravity acceleration applied to its velocity regardless (which I think is good, right?). Collisions with walls are as they used to be and work very well. It's just this last bit of "stickiness" to deal with. The camera is constantly jittering up and down by extremely small fractions too when the ball is "at rest". I'll keep playing with it... I like puzzles like this, especially when I think I'm close. Any final ideas on what I could be doing wrong here? UPDATE 2 Good news - I discovered I should be subtracting the intersection.diff from the m_position (position prior to collision). The intersection.diff is my calculation of the difference in the vector of position to destPosition from the intersection point to the position. In this case, adding it was causing my ball to always go "up" just a little bit, causing the jitter. By subtracting it, and moving that clamper for the velocity.z when close to zero to being above the dot product (and changing the test from <= 0 to < 0), I now have the following: // Clamp z-velocity to zero if we are within a certain threshold float diff = 0.2f - abs(m_velocity.z); if (diff > 0.0f && diff <= 0.2f) { m_velocity.z = 0.0f; } // if we are moving in the direction of the plane (against the normal)... float dotprod = m_velocity.dot(intersection.plane.normal); if (dotprod < 0.0f) { float dampeningForce = 1.8f; // eventually create this value based on mass and acceleration? // Calculate the projection velocity PVRTVec3 actingVelocity = m_velocity.project(intersection.plane.normal); m_velocity -= actingVelocity * dampeningForce; } // Take this object to its new destination position based on... // -- our pre-collision position + vector to the collision point + our new velocity after collision * time // -- remaining after the collision to finish the movement m_destPosition = m_position - intersection.diff + (m_velocity * intersection.tRemaining * GAMESTATE->dt); UpdateWorldMatrix(m_destWorldMatrix, m_destOBB, m_destPosition, false); This is MUCH better. No jitter, and the ball now "rests" at the floor, while still bouncing off the floor and walls. The ONLY thing left is that the ball is now virtually "stuck". He can move but at a much slower rate, likely because the else of my dot product test is only letting the ball move at a rate multiplied against the tRemaining... I think this is a better solution than I had previously, but still somehow not the right idea. BTW, I'm trying to journal my progress through this problem for anyone else with a similar situation - hopefully it will serve as some help, as many similar posts have for me over the years.

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  • Java :moving ball with angle ?

    - by Meko
    Hi all.I am started to learn game physics and I am trying to move ball with an angle.But it does not change its angle .Java coordinate sydstem is a little different and i think my problem is there.Here my codes this is for calculating x and y speed scale_X= Math.sin(angle); scale_Y=Math.cos(angle); velosity_X=(speed*scale_X); velosity_Y=(speed*scale_Y); This is for moving ball in run() function ball.posX =ball.posX+(int)velosity_X; ball.posY=ball.posY+(int)velosity_Y; I used (int)velosity_X and (int)velosity_Y because in ball class I draw object g.drawOval(posX, posX, width, height); and here g.drawOval requares int.I dont know is it problem or not. Also if I use angle 30 it goes +X and +Y but if I use angle 35 it goes -X and -Y. I didnot figure out how work coordinate system on java.

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