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Any reliable polygon normal calculation code?

- by Jenko

I'm currently calculating the normal vector of a polygon using this code, but for some faces here and there it calculates a wrong normal. I don't really know what's going on or where it fails but its not reliable. Do you have any polygon normal calculation that's tested and found to be reliable? // calculate normal of a polygon using all points var n:int = points.length; var x:Number = 0; var y:Number = 0; var z:Number = 0 // ensure all points above 0 var minx:Number = 0, miny:Number = 0, minz:Number = 0; for (var p:int = 0, pl:int = points.length; p < pl; p++) { var po:_Point3D = points[p] = points[p].clone(); if (po.x < minx) { minx = po.x; } if (po.y < miny) { miny = po.y; } if (po.z < minz) { minz = po.z; } } for (p = 0; p < pl; p++) { po = points[p]; po.x -= minx; po.y -= miny; po.z -= minz; } var cur:int = 1, prev:int = 0, next:int = 2; for (var i:int = 1; i <= n; i++) { // using Newell method x += points[cur].y * (points[next].z - points[prev].z); y += points[cur].z * (points[next].x - points[prev].x); z += points[cur].x * (points[next].y - points[prev].y); cur = (cur+1) % n; next = (next+1) % n; prev = (prev+1) % n; } // length of the normal var length:Number = Math.sqrt(x * x + y * y + z * z); // turn large values into a unit vector if (length != 0){ x = x / length; y = y / length; z = z / length; }else { throw new Error("Cannot calculate normal since triangle has an area of 0"); }

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UDP Code client server architecture

- by GameBuilder

Hi I have developed a game on android.Now I want to play it on wifi or 3G. I have game packets which i want to send it form client(mobile) to server then to another client2(mobile). I don't know how to write code in Java to send the playPackets continuously to server and receive the playPacket continuously from the server to the clients. I guess i have to use two thread one for sending and one for receiving. Can someone help me with the code, or the procedure to write code for it. Thanks in advance.

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How to I access "Deny" message from a Lidgren client?

- by TJ Mott

I'm using the Lidgren v3 network for a UDP client/server networking model. On the server end, I'm initializing a NetServer object with the NetIncomingMessage.ConnectionApproval message type enabled. So the client is able to successfully connect and the first packet it sends is a login packet, containing a username and password supplied by the user. The server is receiving that and doing some black magic to authenticate, and everything works up to that point. If the login fails, the server calling NetIncomingMessage.SenderConnection.Deny("Invalid Login Credentials"). I want to know how to properly receive this deny message on the client. I'm getting the message, it shows up with a message type of NetIncomingMessage.StatusChanged. If I call ReadString on that message, I get a corrupted version of the string I passed to the Deny method on the server. The type of corruption varies, I've seen odd characters in there but in every case it's truncated and is way shorter than the string I entered. Any ideas? The official documentation is sparse on this topic. I could use pointers from anyone who has successfully used the Lidgren library and uses the Accept or Deny methods. Also, if I don't do any authentication and just Approve() the connection every time, stuff actually works just fine and I'm getting reliable two-way UDP traffic. (And lastly, Stack Exchange said I don't have enough reputation to use the "Lidgren" tag....???)

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Undefined fireball movement behavior

- by optimisez

Demonstration video I try to do after the player shoot 10 times of fireball, then delete all the fireball objects and recreate a 10 new set of fireball objects. I did it but there is a weird bug happens that sometimes the fireball will come out from top and move to the right after shooting a few times. All the 10 fireballs should follow the player all the time and all the fireball should come out from player even after a new set of fireballs is recreated. Any ideas to fix it? Variables typedef struct gameObject{ float X; float Y; int length; int height; bool action; }; // Fireball #define FIREBALL_NUM 10 LPDIRECT3DTEXTURE9 fireball = NULL; RECT fireballRect; gameObject *fireballDest = new gameObject[FIREBALL_NUM]; int iFireBallAnimation; int fireballCount = 0; Set up Fireball void setUpFireBall() { // Initialize destination rectangle, rectangle height and length for (int i = 0; i < FIREBALL_NUM; i++) { fireballDest[i].X = 0; fireballDest[i].Y = 0; fireballDest[i].length = fireballRect.right - fireballRect.left; fireballDest[i].height = fireballRect.bottom - fireballRect.top; } iFireBallAnimation = fireballRect.right - fireballRect.left; // Initialize boolean for (int i = 0; i < FIREBALL_NUM; i++) { fireballDest[i].action = false; } } Initialize fireball void initFireball() { hr = D3DXCreateTextureFromFileEx(d3dDevice, "fireball.png", 512, 512, D3DX_DEFAULT, NULL, D3DFMT_A8R8G8B8, D3DPOOL_MANAGED, D3DX_DEFAULT, D3DX_DEFAULT, D3DCOLOR_XRGB(255, 255, 0), NULL, NULL, &fireball); // Initialize source rectangle fireballRect.left = 0; fireballRect.top = 256; fireballRect.right = 64; fireballRect.bottom = 320; setUpFireBall(); } Update fireball void update() { updateAnimation(); updateAI(); updatePhysics(); updateGameState(); } void updatePhysics() { motion(); collison(); } void motion() { playerMove(); playerJump(); playerGravity(); shootFireball(); fireballFollowPlayer(); } void shootFireball() { if (keyArr['Z']) fireballDest[fireballCount].action = true; if (fireballDest[fireballCount].action) { fireballDest[fireballCount].X += 10; if (fireballDest[fireballCount].X > 800) fireballCount++; } } void fireballFollowPlayer() { for (int i = 0; i < FIREBALL_NUM; i++) { if (fireballDest[i].action == false) { fireballDest[i].X = playerDest.X - 30; fireballDest[i].Y = playerDest.Y - 14; } } } void updateGameState() { // When no more fireball left, rearm fireball if (fireballCount == FIREBALL_NUM) { delete[] fireballDest; fireballDest = new gameObject[10]; fireballCount = 0; setUpFireBall(); } } Render fireball void renderFireball() { for (int i = 0; i < FIREBALL_NUM; i++) { if (fireballDest[i].action) sprite->Draw(fireball, &fireballRect, NULL, &D3DXVECTOR3(fireballDest[i].X, fireballDest[i].Y, 0), D3DCOLOR_XRGB(255,255, 255)); } }

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SpriteFont Exception, no such character?

- by Michal Bozydar Pawlowski

I have such spriteFont: <?xml version="1.0" encoding="utf-8"?>  <XnaContent xmlns:Graphics="Microsoft.Xna.Framework.Content.Pipeline.Graphics"> <Asset Type="Graphics:FontDescription">  <FontName>Segoe UI</FontName>  <Size>20</Size>  <Spacing>0</Spacing>  <UseKerning>true</UseKerning>  <Style>Regular</Style>    <CharacterRegions> <CharacterRegion> <Start>	</Start> <End>	</End> </CharacterRegion> <CharacterRegion> <Start> </Start> <End>Ұ</End> </CharacterRegion> </CharacterRegions> </Asset> </XnaContent> It has the character regions (32-1200) And I get this exception: A first chance exception of type 'System.ArgumentException' occurred in Microsoft.Xna.Framework.Graphics.ni.dll The character '?' (0x0441) is not available in this SpriteFont. If applicable, adjust the font's start and end CharacterRegions to include this character. Parameter name: character Why? I'm drawing the string like this: spriteBatch.DrawString(font24, zasadyText, zasadyTextPos, kolorCzcionki1, -0.05f, Vector2.Zero, 1.0f, SpriteEffects.None, 0.5f) I even changed the spriteFont to cyrillic: <CharacterRegions> <CharacterRegion> <Start>	</Start> <End>	</End> </CharacterRegion> <CharacterRegion> <Start> </Start> <End>ſ</End> </CharacterRegion> <CharacterRegion> <Start>А</Start> <End>ї</End> </CharacterRegion> </CharacterRegions> </Asset> </XnaContent> and it still doesn't work. I got the (0x441 = char) exception -- EDIT -- Ok, I got the solution. It was a letter mistake in language. I had this: if (jezyk == "ru_RU") { font14 = Content.Load<SpriteFont>("ru_font14"); font24 = Content.Load<SpriteFont>("ru_font24"); font12 = Content.Load<SpriteFont>("ru_czcionkaFloty"); font10 = Content.Load<SpriteFont>("ru_font10"); font28 = Content.Load<SpriteFont>("ru_font28"); font20 = Content.Load<SpriteFont>("ru_font20"); } else { font14 = Content.Load<SpriteFont>("font14"); font24 = Content.Load<SpriteFont>("font24"); font12 = Content.Load<SpriteFont>("czcionkaFloty"); font10 = Content.Load<SpriteFont>("font10"); font28 = Content.Load<SpriteFont>("font28"); font20 = Content.Load<SpriteFont>("font20"); } and there should be not "ru_RU" but "ru-RU" I have no idea. I changed the spriteFont to cyrillic: <CharacterRegions> <CharacterRegion> <Start>	</Start> <End>	</End> </CharacterRegion> <CharacterRegion> <Start> </Start> <End>ſ</End> </CharacterRegion> <CharacterRegion> <Start>А</Start> <End>ї</End> </CharacterRegion> </CharacterRegions> </Asset> </XnaContent> and it still doesn't work. I got the (0x441 = char) exception

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How to get all keys values of the player prefs in unity [java script ]

- by Akari

in the first test game I've developed if the player passed all the levels and win , he must enter his name ... so his name and his score will be stored in a player prefs : and there is another scene that displays the names and scores of all the user passed the game : I've searched from the morning and try all the ways I know and finally I failed to perform this .... is it possible to display all the keys values previously stored in the player prefs ??? or can someone to provide me by a JavaScript to do this ???? thanks...

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Trying to implement fling events on an object

- by Adam Short

I have a game object, well a bitmap, which I'd like to "fling". I'm struggling to get it to fling ontouchlistener due to it being a bitmap and not sure how to proceed and I'm struggling to find the resources to help. Here's my code so far: https://github.com/addrum/Shapes GameActivity class: package com.main.shapes; import android.app.Activity; import android.content.Context; import android.graphics.Bitmap; import android.graphics.BitmapFactory; import android.graphics.Canvas; import android.os.Bundle; import android.view.GestureDetector; import android.view.MotionEvent; import android.view.SurfaceHolder; import android.view.SurfaceView; import android.view.View.OnTouchListener; import android.view.Window; public class GameActivity extends Activity { private GestureDetector gestureDetector; View view; Bitmap ball; float x, y; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); //Remove title bar this.requestWindowFeature(Window.FEATURE_NO_TITLE); view = new View(this); ball = BitmapFactory.decodeResource(getResources(), R.drawable.ball); gestureDetector = new GestureDetector(this, new GestureListener()); x = 0; y = 0; setContentView(view); ball.setOnTouchListener(new OnTouchListener() { @Override public boolean onTouch(android.view.View v, MotionEvent event) { // TODO Auto-generated method stub return false; } }); } @Override protected void onPause() { super.onPause(); view.pause(); } @Override protected void onResume() { super.onResume(); view.resume(); } public class View extends SurfaceView implements Runnable { Thread thread = null; SurfaceHolder holder; boolean canRun = false; public View(Context context) { super(context); holder = getHolder(); } public void run() { while (canRun) { if (!holder.getSurface().isValid()) { continue; } Canvas c = holder.lockCanvas(); c.drawARGB(255, 255, 255, 255); c.drawBitmap(ball, x - (ball.getWidth() / 2), y - (ball.getHeight() / 2), null); holder.unlockCanvasAndPost(c); } } public void pause() { canRun = false; while (true) { try { thread.join(); } catch (InterruptedException e) { e.printStackTrace(); } break; } thread = null; } public void resume() { canRun = true; thread = new Thread(this); thread.start(); } } } GestureListener class: package com.main.shapes; import android.view.GestureDetector.SimpleOnGestureListener; import android.view.MotionEvent; public class GestureListener extends SimpleOnGestureListener { private static final int SWIPE_MIN_DISTANCE = 120; private static final int SWIPE_THRESHOLD_VELOCITY = 200; @Override public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) { if (e1.getX() - e2.getX() > SWIPE_MIN_DISTANCE && Math.abs(velocityX) > SWIPE_THRESHOLD_VELOCITY) { //From Right to Left return true; } else if (e2.getX() - e1.getX() > SWIPE_MIN_DISTANCE && Math.abs(velocityX) > SWIPE_THRESHOLD_VELOCITY) { //From Left to Right return true; } if (e1.getY() - e2.getY() > SWIPE_MIN_DISTANCE && Math.abs(velocityY) > SWIPE_THRESHOLD_VELOCITY) { //From Bottom to Top return true; } else if (e2.getY() - e1.getY() > SWIPE_MIN_DISTANCE && Math.abs(velocityY) > SWIPE_THRESHOLD_VELOCITY) { //From Top to Bottom return true; } return false; } @Override public boolean onDown(MotionEvent e) { //always return true since all gestures always begin with onDown and<br> //if this returns false, the framework won't try to pick up onFling for example. return true; } }

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Calculating collision force with AfterCollision/NormalImpulse is unreliable when IgnoreCCD = false?

- by Michael

I'm using Farseer Physics Engine 3.3.1 in a very simple XNA 4 test game. (Note: I'm also tagging this Box2D, because Farseer is a direct port of Box2D and I will happily accept Box2D answers that solve this problem.) In this game, I'm creating two bodies. The first body is created using BodyFactory.CreateCircle and BodyType.Dynamic. This body can be moved around using the keyboard (which sets Body.LinearVelocity). The second body is created using BodyFactory.CreateRectangle and BodyType.Static. This body is static and never moves. Then I'm using this code to calculate the force of collision when the two bodies collide: staticBody.FixtureList[0].AfterCollision += new AfterCollisionEventHandler(AfterCollision); protected void AfterCollision(Fixture fixtureA, Fixture fixtureB, Contact contact) { float maxImpulse = 0f; for (int i = 0; i < contact.Manifold.PointCount; i++) maxImpulse = Math.Max(maxImpulse, contact.Manifold.Points[i].NormalImpulse); // maxImpulse should contain the force of the collision } This code works great if both of these bodies are set to IgnoreCCD=true. I can calculate the force of collision between them 100% reliably. Perfect. But here's the problem: If I set the bodies to IgnoreCCD=false, that code becomes wildly unpredictable. AfterCollision is called reliably, but for some reason the NormalImpulse is 0 about 75% of the time, so only about one in four collisions is registered. Worse still, the NormalImpulse seems to be zero for completely random reasons. The dynamic body can collide with the static body 10 times in a row in virtually exactly the same way, and only 2 or 3 of the hits will register with a NormalImpulse greater than zero. Setting IgnoreCCD=true on both bodies instantly solves the problem, but then I lose continuous physics detection. Why is this happening and how can I fix it? Here's a link to a simple XNA 4 solution that demonstrates this problem in action: http://www.mediafire.com/?a1w242q9sna54j4

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Mesh with quads to triangle mesh

- by scape

I want to use Blender for making models yet realize some of the polygons are not triangles but contain quads or more (example: cylinder top and bottom). I could export the the mesh as a basic mesh file and import it in to an openGL application and workout rendering the quads as tris, but anything with more than 4 vert indices is beyond me. Is it typical to convert the mesh to a triangle-based mesh inside blender before exporting it? I actually tried this through the quads_convert_to_tris method within a blender py script and the top of the cylinder does not look symmetrical. What is typically done to render a loaded mesh as a tri?

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Example of DOD design (on a generic Zombie game)

- by Jeffrey

I can't seem to find a nice explanation of the Data Oriented Design for a generic zombie game (it's just an example, pretty common example). Could you make an example of the Data Oriented Design on creating a generic zombie class? Is the following good? Zombie list class: class ZombieList { GLuint vbo; // generic zombie vertex model std::vector<color>; // object default color std::vector<texture>; // objects textures std::vector<vector3D>; // objects positions public: unsigned int create(); // return object id void move(unsigned int objId, vector3D offset); void rotate(unsigned int objId, float angle); void setColor(unsigned int objId, color c); void setPosition(unsigned int objId, color c); void setTexture(unsigned int, unsigned int); ... void update(Player*); // move towards player, attack if near } Example: Player p; Zombielist zl; unsigned int first = zl.create(); zl.setPosition(first, vector3D(50, 50)); zl.setTexture(first, texture("zombie1.png")); ... while (running) { // main loop ... zl.update(&p); zl.draw(); // draw every zombie } Or would creating a generic World container that contains every action from bite(zombieId, playerId) to moveTo(playerId, vector) to createPlayer() to shoot(playerId, vector) to face(radians)/face(vector); and contains: std::vector<zombie> std::vector<player> ... std::vector<mapchunk> ... std::vector<vbobufferid> player_run_animation; ... be a good example? Whats the proper way to organize a game with DOD?

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Combine 3D objects in XNA 4

- by Christoph

Currently I am writing on my thesis for university, the theme I am working on is 3D Visualization of hierarchical structures using cone trees. I want to do is to draw a cone and arrange a number of spheres at the bottom of the cone. The spheres should be arranged according to the radius and the number of spheres correctly. As you can imagine I need a lot of these cone/sphere combinations. First Attempt I was able to find some tutorials that helped with drawing cones and spheres. Cone public Cone(GraphicsDevice device, float height, int tessellation, string name, List<Sphere> children) { //prepare children and calculate the children spacing and radius of the cone if (children == null || children.Count == 0) { throw new ArgumentNullException("children"); } this.Height = height; this.Name = name; this.Children = children; //create the cone if (tessellation < 3) { throw new ArgumentOutOfRangeException("tessellation"); } //Create a ring of triangels around the outside of the cones bottom for (int i = 0; i < tessellation; i++) { Vector3 normal = this.GetCircleVector(i, tessellation); // add the vertices for the top of the cone base.AddVertex(Vector3.Up * height, normal); //add the bottom circle base.AddVertex(normal * this.radius + Vector3.Down * height, normal); //Add indices base.AddIndex(i * 2); base.AddIndex(i * 2 + 1); base.AddIndex((i * 2 + 2) % (tessellation * 2)); base.AddIndex(i * 2 + 1); base.AddIndex((i * 2 + 3) % (tessellation * 2)); base.AddIndex((i * 2 + 2) % (tessellation * 2)); } //create flate triangle to seal the bottom this.CreateCap(tessellation, height, this.Radius, Vector3.Down); base.InitializePrimitive(device); } Sphere public void Initialize(GraphicsDevice device, Vector3 qi) { int verticalSegments = this.Tesselation; int horizontalSegments = this.Tesselation * 2; //single vertex on the bottom base.AddVertex((qi * this.Radius) + this.lowering, Vector3.Down); for (int i = 0; i < verticalSegments; i++) { float latitude = ((i + 1) * MathHelper.Pi / verticalSegments) - MathHelper.PiOver2; float dy = (float)Math.Sin(latitude); float dxz = (float)Math.Cos(latitude); //Create a singe ring of latitudes for (int j = 0; j < horizontalSegments; j++) { float longitude = j * MathHelper.TwoPi / horizontalSegments; float dx = (float)Math.Cos(longitude) * dxz; float dz = (float)Math.Sin(longitude) * dxz; Vector3 normal = new Vector3(dx, dy, dz); base.AddVertex(normal * this.Radius, normal); } } // Finish with a single vertex at the top of the sphere. AddVertex((qi * this.Radius) + this.lowering, Vector3.Up); // Create a fan connecting the bottom vertex to the bottom latitude ring. for (int i = 0; i < horizontalSegments; i++) { AddIndex(0); AddIndex(1 + (i + 1) % horizontalSegments); AddIndex(1 + i); } // Fill the sphere body with triangles joining each pair of latitude rings. for (int i = 0; i < verticalSegments - 2; i++) { for (int j = 0; j < horizontalSegments; j++) { int nextI = i + 1; int nextJ = (j + 1) % horizontalSegments; base.AddIndex(1 + i * horizontalSegments + j); base.AddIndex(1 + i * horizontalSegments + nextJ); base.AddIndex(1 + nextI * horizontalSegments + j); base.AddIndex(1 + i * horizontalSegments + nextJ); base.AddIndex(1 + nextI * horizontalSegments + nextJ); base.AddIndex(1 + nextI * horizontalSegments + j); } } // Create a fan connecting the top vertex to the top latitude ring. for (int i = 0; i < horizontalSegments; i++) { base.AddIndex(CurrentVertex - 1); base.AddIndex(CurrentVertex - 2 - (i + 1) % horizontalSegments); base.AddIndex(CurrentVertex - 2 - i); } base.InitializePrimitive(device); } The tricky part now is to arrange the spheres at the bottom of the cone. I tried is to draw just the cone and then draw the spheres. I need a lot of these cones, so it would be pretty hard to calculate all the positions correctly. Second Attempt So the second try was to generate a object that builds all vertices of the cone and all of the spheres at once. So I was hoping to render a cone with all its spheres arranged correctly. After a short debug I found out that the cone is created and the first sphere, when it turn of the second sphere I am running into an OutOfBoundsException of ushort.MaxValue. Cone and Spheres public ConeWithSpheres(GraphicsDevice device, float height, float coneDiameter, float sphereDiameter, int coneTessellation, int sphereTessellation, int numberOfSpheres) { if (coneTessellation < 3) { throw new ArgumentException(string.Format("{0} is to small for the tessellation of the cone. The number must be greater or equal to 3", coneTessellation)); } if (sphereTessellation < 3) { throw new ArgumentException(string.Format("{0} is to small for the tessellation of the sphere. The number must be greater or equal to 3", sphereTessellation)); } //set properties this.Height = height; this.ConeDiameter = coneDiameter; this.SphereDiameter = sphereDiameter; this.NumberOfChildren = numberOfSpheres; //end set properties //generate the cone this.GenerateCone(device, coneTessellation); //generate the spheres //vector that defines the Y position of the sphere on the cones bottom Vector3 lowering = new Vector3(0, 0.888f, 0); this.GenerateSpheres(device, sphereTessellation, numberOfSpheres, lowering); } // ------ GENERATE CONE ------ private void GenerateCone(GraphicsDevice device, int coneTessellation) { int doubleTessellation = coneTessellation * 2; //Create a ring of triangels around the outside of the cones bottom for (int index = 0; index < coneTessellation; index++) { Vector3 normal = this.GetCircleVector(index, coneTessellation); //add the vertices for the top of the cone base.AddVertex(Vector3.Up * this.Height, normal); //add the bottom of the cone base.AddVertex(normal * this.ConeRadius + Vector3.Down * this.Height, normal); //add indices base.AddIndex(index * 2); base.AddIndex(index * 2 + 1); base.AddIndex((index * 2 + 2) % doubleTessellation); base.AddIndex(index * 2 + 1); base.AddIndex((index * 2 + 3) % doubleTessellation); base.AddIndex((index * 2 + 2) % doubleTessellation); } //create flate triangle to seal the bottom this.CreateCap(coneTessellation, this.Height, this.ConeRadius, Vector3.Down); base.InitializePrimitive(device); } // ------ GENERATE SPHERES ------ private void GenerateSpheres(GraphicsDevice device, int sphereTessellation, int numberOfSpheres, Vector3 lowering) { int verticalSegments = sphereTessellation; int horizontalSegments = sphereTessellation * 2; for (int childCount = 1; childCount < numberOfSpheres; childCount++) { //single vertex at the bottom of the sphere base.AddVertex((this.GetCircleVector(childCount, this.NumberOfChildren) * this.SphereRadius) + lowering, Vector3.Down); for (int verticalSegmentsCount = 0; verticalSegmentsCount < verticalSegments; verticalSegmentsCount++) { float latitude = ((verticalSegmentsCount + 1) * MathHelper.Pi / verticalSegments) - MathHelper.PiOver2; float dy = (float)Math.Sin(latitude); float dxz = (float)Math.Cos(latitude); //create a single ring of latitudes for (int horizontalSegmentsCount = 0; horizontalSegmentsCount < horizontalSegments; horizontalSegmentsCount++) { float longitude = horizontalSegmentsCount * MathHelper.TwoPi / horizontalSegments; float dx = (float)Math.Cos(longitude) * dxz; float dz = (float)Math.Sin(longitude) * dxz; Vector3 normal = new Vector3(dx, dy, dz); base.AddVertex((normal * this.SphereRadius) + lowering, normal); } } //finish with a single vertex at the top of the sphere base.AddVertex((this.GetCircleVector(childCount, this.NumberOfChildren) * this.SphereRadius) + lowering, Vector3.Up); //create a fan connecting the bottom vertex to the bottom latitude ring for (int i = 0; i < horizontalSegments; i++) { base.AddIndex(0); base.AddIndex(1 + (i + 1) % horizontalSegments); base.AddIndex(1 + i); } //Fill the sphere body with triangles joining each pair of latitude rings for (int i = 0; i < verticalSegments - 2; i++) { for (int j = 0; j < horizontalSegments; j++) { int nextI = i + 1; int nextJ = (j + 1) % horizontalSegments; base.AddIndex(1 + i * horizontalSegments + j); base.AddIndex(1 + i * horizontalSegments + nextJ); base.AddIndex(1 + nextI * horizontalSegments + j); base.AddIndex(1 + i * horizontalSegments + nextJ); base.AddIndex(1 + nextI * horizontalSegments + nextJ); base.AddIndex(1 + nextI * horizontalSegments + j); } } //create a fan connecting the top vertiex to the top latitude for (int i = 0; i < horizontalSegments; i++) { base.AddIndex(this.CurrentVertex - 1); base.AddIndex(this.CurrentVertex - 2 - (i + 1) % horizontalSegments); base.AddIndex(this.CurrentVertex - 2 - i); } base.InitializePrimitive(device); } } Any ideas how I could fix this?

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Physics System ignores collision in some rare cases

- by Gajoo

I've been developing a simple physics engine for my game. since the game physics is very simple I've decided to increase accuracy a little bit. Instead of formal integration methods like fourier or RK4, I'm directly computing the results after delta time "dt". based on the very first laws of physics : dx = 0.5 * a * dt^2 + v0 * dt dv = a * dt where a is acceleration and v0 is object's previous velocity. Also to handle collisions I've used a method which is somehow different from those I've seen so far. I'm detecting all the collision in the given time frame, stepping the world forward to the nearest collision, resolving it and again check for possible collisions. As I said the world consist of very simple objects, so I'm not loosing any performance due to multiple collision checking. First I'm checking if the ball collides with any walls around it (which is working perfectly) and then I'm checking if it collides with the edges of the walls (yellow points in the picture). the algorithm seems to work without any problem except some rare cases, in which the collision with points are ignored. I've tested everything and all the variables seem to be what they should but after leaving the system work for a minute or two the system the ball passes through one of those points. Here is collision portion of my code, hopefully one of you guys can give me a hint where to look for a potential bug! void PhysicalWorld::checkForPointCollision(Vec2 acceleration, PhysicsComponent& ball, Vec2& collisionNormal, float& collisionTime, Vec2 target) { // this function checks if there will be any collision between a circle and a point // ball contains informations about the circle (it's current velocity, position and radius) // collisionNormal is an output variable // collisionTime is also an output varialbe // target is the point I want to check for collisions Vec2 V = ball.mVelocity; Vec2 A = acceleration; Vec2 P = ball.mPosition - target; float wallWidth = mMap->getWallWidth() / (mMap->getWallWidth() + mMap->getHallWidth()) / 2; float r = ball.mRadius / (mMap->getWallWidth() + mMap->getHallWidth()); // r is ball radius scaled to match actual rendered object. if (A.any()) // todo : I need to first correctly solve the collisions in case there is no acceleration return; if (V.any()) // if object is not moving there will be no collisions! { float D = P.x * V.y - P.y * V.x; float Delta = r*r*V.length2() - D*D; if(Delta < eps) return; Delta = sqrt(Delta); float sgnvy = V.y > 0 ? 1: (V.y < 0?-1:0); Vec2 c1(( D*V.y+sgnvy*V.x*Delta) / V.length2(), (-D*V.x+fabs(V.y)*Delta) / V.length2()); Vec2 c2(( D*V.y-sgnvy*V.x*Delta) / V.length2(), (-D*V.x-fabs(V.y)*Delta) / V.length2()); float t1 = (c1.x - P.x) / V.x; float t2 = (c2.x - P.x) / V.x; if(t1 > eps && t1 <= collisionTime) { collisionTime = t1; collisionNormal = c1; } if(t2 > eps && t2 <= collisionTime) { collisionTime = t2; collisionNormal = c2; } } } // this function should step the world forward by dt. it doesn't check for collision of any two balls (components) // it just checks if there is a collision between the current component and 4 points forming a rectangle around it. void PhysicalWorld::step(float dt) { for (unsigned i=0;i<mObjects.size();i++) { PhysicsComponent &current = *mObjects[i]; Vec2 acceleration = current.mForces * current.mInvMass; float rt=dt; // stores how much more the world should advance while(rt > eps) { float collisionTime = rt; Vec2 collisionNormal = Vec2(0,0); float halfWallWidth = mMap->getWallWidth() / (mMap->getWallWidth() + mMap->getHallWidth()) / 2; // we check if there is any collision with any of those 4 points around the ball // if there is a collision both collisionNormal and collisionTime variables will change // after these functions collisionTime will be exactly the value of nearest collision (if any) // and if there was, collisionNormal will report in which direction the ball should return. checkForPointCollision(acceleration,current,collisionNormal,collisionTime,Vec2(floor(current.mPosition.x) + halfWallWidth,floor(current.mPosition.y) + halfWallWidth)); checkForPointCollision(acceleration,current,collisionNormal,collisionTime,Vec2(floor(current.mPosition.x) + halfWallWidth, ceil(current.mPosition.y) - halfWallWidth)); checkForPointCollision(acceleration,current,collisionNormal,collisionTime,Vec2( ceil(current.mPosition.x) - halfWallWidth,floor(current.mPosition.y) + halfWallWidth)); checkForPointCollision(acceleration,current,collisionNormal,collisionTime,Vec2( ceil(current.mPosition.x) - halfWallWidth, ceil(current.mPosition.y) - halfWallWidth)); // either if there is a collision or if there is not we step the forward since we are sure there will be no collision before collisionTime current.mPosition += collisionTime * (collisionTime * acceleration * 0.5 + current.mVelocity); current.mVelocity += collisionTime * acceleration; // if the ball collided with anything collisionNormal should be at least none zero in one of it's axis if (collisionNormal.any()) { collisionNormal *= Dot(collisionNormal, current.mVelocity) / collisionNormal.length2(); current.mVelocity -= 2 * collisionNormal; // simply reverse velocity along collision normal direction } rt -= collisionTime; } // reset all forces for current object so it'll be ready for later game event current.mForces.zero(); } }

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Doing powerups in a component-based system

- by deft_code

I'm just starting really getting my head around component based design. I don't know what the "right" way to do this is. Here's the scenario. The player can equip a shield. The the shield is drawn as bubble around the player, it has a separate collision shape, and reduces the damage the player receives from area effects. How is such a shield architected in a component based game? Where I get confused is that the shield obviously has three components associated with it. Damage reduction / filtering A sprite A collider. To make it worse different shield variations could have even more behaviors, all of which could be components: boost player maximum health health regen projectile deflection etc Am I overthinking this? Should the shield just be a super component? I really think this is wrong answer. So if you think this is the way to go please explain. Should the shield be its own entity that tracks the location of the player? That might make it hard to implement the damage filtering. It also kinda blurs the lines between attached components and entities. Should the shield be a component that houses other components? I've never seen or heard of anything like this, but maybe it's common and I'm just not deep enough yet. Should the shield just be a set of components that get added to the player? Possibly with an extra component to manage the others, e.g. so they can all be removed as a group. (accidentally leave behind the damage reduction component, now that would be fun). Something else that's obvious to someone with more component experience?

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Managing flash animations for a game

- by LoveMeSomeCode

Ok, I've been writing C# for a while, but I'm new to ActionScript, so this is a question about best practices. We're developing a simple match game, where the user selects tiles and tries to match various numbers - sort of like memory - and when the match is made we want a series of animations to take place, and when they're done, remove the tile and add a new one. So basically it's: User clicks the MC Animation 1 on the MC starts Animation 1 ends Remove the MC from the stage Add a new MC Start the animation on the new MC The problem I run into is that I don't want to make the same timeline motion tween on each and every tile, when the animation is all the same. It's just the picture in the tile that's different. The other method I've come up with is to just apply the tweens in code on the main stage. Then I attach an event handler for MOTION_FINISH, and in that handler I trigger the next animation and listen for that to finish etc. This works too, but not only do I have to do all the tweening in code, I have a seperate event handler for each stage of the animation. So is there a more structured way of chaining these animations together?

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Smooth animation when using fixed time step

- by sythical

I'm trying to implement the game loop where the physics is independent from rendering but my animation isn't as smooth as I would like it to be and it seems to periodically jump. Here is my code: // alpha is used for interpolation double alpha = 0, counter_old_time = 0; double accumulator = 0, delta_time = 0, current_time = 0, previous_time = 0; unsigned frame_counter = 0, current_fps = 0; const unsigned physics_rate = 40, max_step_count = 5; const double step_duration = 1.0 / 40.0, accumulator_max = step_duration * 5; // information about the circ;e (position and velocity) int old_pos_x = 100, new_pos_x = 100, render_pos_x = 100, velocity_x = 60; previous_time = al_get_time(); while(true) { current_time = al_get_time(); delta_time = current_time - previous_time; previous_time = current_time; accumulator += delta_time; if(accumulator > accumulator_max) { accumulator = accumulator_max; } while(accumulator >= step_duration) { if(new_pos_x > 1330) velocity_x = -15; else if(new_pos_x < 70) velocity_x = 15; old_pos_x = new_pos_x; new_pos_x += velocity_x; accumulator -= step_duration; } alpha = accumulator / static_cast<double>(step_duration); render_pos_x = old_pos_x + (new_pos_x - old_pos_x) * alpha; al_clear_to_color(al_map_rgb(20, 20, 40)); // clears the screen al_draw_textf(font, al_map_rgb(255, 255, 255), 20, 20, 0, "current_fps: %i", current_fps); // print fps al_draw_filled_circle(render_pos_x, 400, 15, al_map_rgb(255, 255, 255)); // draw circle // I've added this to test how the program will behave when rendering takes // considerably longer than updating the game. al_rest(0.008); al_flip_display(); // swaps the buffers frame_counter++; if(al_get_time() - counter_old_time >= 1) { current_fps = frame_counter; frame_counter = 0; counter_old_time = al_get_time(); } } I have added a pause during the rendering part because I wanted to see how the code would behave when a lot of rendering is involved. Removing it makes the animation smooth but then I'll have to make sure that I don't let the frame rate drop too much and that doesn't seem like a good solution. I've been trying to fix this for a week and have had no luck so I'd be very grateful if someone can read through my code. Thank you! Edit: I added the following code to work out the actual velocity (pixels per second) of the ball each time the ball is rendered and surprisingly it's not constant so I'm guessing that's the issue. I'm not sure why it's not constant. alpha = accumulator / static_cast<double>(step_duration); render_pos_x = old_pos_x + (new_pos_x - old_pos_x) * alpha; cout << (render_pos_x - old_render_pos) / delta_time << endl; old_render_pos = render_pos_x;

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What are the maths behind 'Raiden 2' purple laser?

- by Aybe

The path of the laser is affected by user input and enemies present on the screen. Here is a video, at 5:00 minutes the laser in question is shown : Raiden II (PS) - 1 Loop Clear - Part 2 UPDATE Here is a test using Inkscape, ship is at bottom, the first 4 enemies are targeted by the plasma. There seems to be a sort of pattern. I moved the ship first, then the handle from it to form a 45° angle, then while trying to fit the curve I found a pattern of parallel handles and continued so until I reached the last enemy. Update, 5/26/2012 : I started an XNA project using beziers, there is still some work needed, will update the question next week. Stay tuned ! Update : 5/30/2012 : It really seems that they are using Bézier curves, I think I will be able to replicate/imitate a plasma of such grade. There are two new topics I discovered since last time : Arc length, Runge's phenomenon, first one should help in having a linear movement possible over a Bézier curve, second should help in optimizing the number of vertices. Next time I will put a video so you can see the progress 8-)

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Pathfinding results in false path costs that are too high

- by user2144536

I'm trying to implement pathfinding in a game I'm programming using this method. I'm implementing it with recursion but some of the values after the immediate circle of tiles around the player are way off. For some reason I cannot find the problem with it. This is a screen cap of the problem: The pathfinding values are displayed in the center of every tile. Clipped blocks are displayed with the value of 'c' because the values were too high and were covering up the next value. The red circle is the first value that is incorrect. The code below is the recursive method. //tileX is the coordinates of the current tile, val is the current pathfinding value, used[][] is a boolean //array to keep track of which tiles' values have already been assigned public void pathFind(int tileX, int tileY, int val, boolean[][] used) { //increment pathfinding value int curVal = val + 1; //set current tile to true if it hasn't been already used[tileX][tileY] = true; //booleans to know which tiles the recursive call needs to be used on boolean topLeftUsed = false, topUsed = false, topRightUsed = false, leftUsed = false, rightUsed = false, botomLeftUsed = false, botomUsed = false, botomRightUsed = false; //set value of top left tile if necessary if(tileX - 1 >= 0 && tileY - 1 >= 0) { //isClipped(int x, int y) returns true if the coordinates givin are in a tile that can't be walked through (IE walls) //occupied[][] is an array that keeps track of which tiles have an enemy in them // //if the tile is not clipped and not occupied set the pathfinding value if(isClipped((tileX - 1) * 50 + 25, (tileY - 1) * 50 + 25) == false && occupied[tileX - 1][tileY - 1] == false && !(used[tileX - 1][tileY - 1])) { pathFindingValues[tileX - 1][tileY - 1] = curVal; topLeftUsed = true; used[tileX - 1][tileY - 1] = true; } //if it is occupied set it to an arbitrary high number so enemies find alternate routes if the best is clogged if(occupied[tileX - 1][tileY - 1] == true) pathFindingValues[tileX - 1][tileY - 1] = 1000000000; //if it is clipped set it to an arbitrary higher number so enemies don't travel through walls if(isClipped((tileX - 1) * 50 + 25, (tileY - 1) * 50 + 25) == true) pathFindingValues[tileX - 1][tileY - 1] = 2000000000; } //top middle if(tileY - 1 >= 0 ) { if(isClipped(tileX * 50 + 25, (tileY - 1) * 50 + 25) == false && occupied[tileX][tileY - 1] == false && !(used[tileX][tileY - 1])) { pathFindingValues[tileX][tileY - 1] = curVal; topUsed = true; used[tileX][tileY - 1] = true; } if(occupied[tileX][tileY - 1] == true) pathFindingValues[tileX][tileY - 1] = 1000000000; if(isClipped(tileX * 50 + 25, (tileY - 1) * 50 + 25) == true) pathFindingValues[tileX][tileY - 1] = 2000000000; } //top right if(tileX + 1 <= used.length && tileY - 1 >= 0) { if(isClipped((tileX + 1) * 50 + 25, (tileY - 1) * 50 + 25) == false && occupied[tileX + 1][tileY - 1] == false && !(used[tileX + 1][tileY - 1])) { pathFindingValues[tileX + 1][tileY - 1] = curVal; topRightUsed = true; used[tileX + 1][tileY - 1] = true; } if(occupied[tileX + 1][tileY - 1] == true) pathFindingValues[tileX + 1][tileY - 1] = 1000000000; if(isClipped((tileX + 1) * 50 + 25, (tileY - 1) * 50 + 25) == true) pathFindingValues[tileX + 1][tileY - 1] = 2000000000; } //left if(tileX - 1 >= 0) { if(isClipped((tileX - 1) * 50 + 25, (tileY) * 50 + 25) == false && occupied[tileX - 1][tileY] == false && !(used[tileX - 1][tileY])) { pathFindingValues[tileX - 1][tileY] = curVal; leftUsed = true; used[tileX - 1][tileY] = true; } if(occupied[tileX - 1][tileY] == true) pathFindingValues[tileX - 1][tileY] = 1000000000; if(isClipped((tileX - 1) * 50 + 25, (tileY) * 50 + 25) == true) pathFindingValues[tileX - 1][tileY] = 2000000000; } //right if(tileX + 1 <= used.length) { if(isClipped((tileX + 1) * 50 + 25, (tileY) * 50 + 25) == false && occupied[tileX + 1][tileY] == false && !(used[tileX + 1][tileY])) { pathFindingValues[tileX + 1][tileY] = curVal; rightUsed = true; used[tileX + 1][tileY] = true; } if(occupied[tileX + 1][tileY] == true) pathFindingValues[tileX + 1][tileY] = 1000000000; if(isClipped((tileX + 1) * 50 + 25, (tileY) * 50 + 25) == true) pathFindingValues[tileX + 1][tileY] = 2000000000; } //botom left if(tileX - 1 >= 0 && tileY + 1 <= used[0].length) { if(isClipped((tileX - 1) * 50 + 25, (tileY + 1) * 50 + 25) == false && occupied[tileX - 1][tileY + 1] == false && !(used[tileX - 1][tileY + 1])) { pathFindingValues[tileX - 1][tileY + 1] = curVal; botomLeftUsed = true; used[tileX - 1][tileY + 1] = true; } if(occupied[tileX - 1][tileY + 1] == true) pathFindingValues[tileX - 1][tileY + 1] = 1000000000; if(isClipped((tileX - 1) * 50 + 25, (tileY + 1) * 50 + 25) == true) pathFindingValues[tileX - 1][tileY + 1] = 2000000000; } //botom middle if(tileY + 1 <= used[0].length) { if(isClipped((tileX) * 50 + 25, (tileY + 1) * 50 + 25) == false && occupied[tileX][tileY + 1] == false && !(used[tileX][tileY + 1])) { pathFindingValues[tileX][tileY + 1] = curVal; botomUsed = true; used[tileX][tileY + 1] = true; } if(occupied[tileX][tileY + 1] == true) pathFindingValues[tileX][tileY + 1] = 1000000000; if(isClipped((tileX) * 50 + 25, (tileY + 1) * 50 + 25) == true) pathFindingValues[tileX][tileY + 1] = 2000000000; } //botom right if(tileX + 1 <= used.length && tileY + 1 <= used[0].length) { if(isClipped((tileX + 1) * 50 + 25, (tileY + 1) * 50 + 25) == false && occupied[tileX + 1][tileY + 1] == false && !(used[tileX + 1][tileY + 1])) { pathFindingValues[tileX + 1][tileY + 1] = curVal; botomRightUsed = true; used[tileX + 1][tileY + 1] = true; } if(occupied[tileX + 1][tileY + 1] == true) pathFindingValues[tileX + 1][tileY + 1] = 1000000000; if(isClipped((tileX + 1) * 50 + 25, (tileY + 1) * 50 + 25) == true) pathFindingValues[tileX + 1][tileY + 1] = 2000000000; } //call the method on the tiles that need it if(tileX - 1 >= 0 && tileY - 1 >= 0 && topLeftUsed) pathFind(tileX - 1, tileY - 1, curVal, used); if(tileY - 1 >= 0 && topUsed) pathFind(tileX , tileY - 1, curVal, used); if(tileX + 1 <= used.length && tileY - 1 >= 0 && topRightUsed) pathFind(tileX + 1, tileY - 1, curVal, used); if(tileX - 1 >= 0 && leftUsed) pathFind(tileX - 1, tileY, curVal, used); if(tileX + 1 <= used.length && rightUsed) pathFind(tileX + 1, tileY, curVal, used); if(tileX - 1 >= 0 && tileY + 1 <= used[0].length && botomLeftUsed) pathFind(tileX - 1, tileY + 1, curVal, used); if(tileY + 1 <= used[0].length && botomUsed) pathFind(tileX, tileY + 1, curVal, used); if(tileX + 1 <= used.length && tileY + 1 <= used[0].length && botomRightUsed) pathFind(tileX + 1, tileY + 1, curVal, used); }

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Objective C - Aggro with Images

- by Will

I have three UIImageViews. enemy1, enemy1AggroBox and mainSprite. What I want to do is when mainSprite and enemy1AggroBox interect, I want enemy1 to start moving towards mainSprite. Basically creating aggro for a game. if(CGRectIntersectsRect(mainSprite.frame, enemy1AggroBox.frame)){ //Code here// } My plan would be to call this method in viewDidLoad. I'm not using any sort of framework like cocos2d or OpenGLES. If you need to see any more code just ask.

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2D Tile Based Collision Detection

- by MrPlosion1243

There are a lot of topics about this and it seems each one addresses a different problem, this topic does the same. I was looking into tile collision detection and found this where David Gouveia explains a great way to get around the person's problem by separating the two axis. So I implemented the solution and it all worked perfectly from all the testes I through at it. Then I implemented more advanced platforming physics and the collision detection broke down. Unfortunately I have not been able to get it to work again which is where you guys come in :)! I will present the code first: public void Update(GameTime gameTime) { if(Input.GetKeyDown(Keys.A)) { velocity.X -= moveAcceleration; } else if(Input.GetKeyDown(Keys.D)) { velocity.X += moveAcceleration; } if(Input.GetKeyDown(Keys.Space)) { if((onGround && isPressable) || (!onGround && airTime <= maxAirTime && isPressable)) { onGround = false; airTime += (float)gameTime.ElapsedGameTime.TotalSeconds; velocity.Y = initialJumpVelocity * (1.0f - (float)Math.Pow(airTime / maxAirTime, Math.PI)); } } else if(Input.GetKeyReleased(Keys.Space)) { isPressable = false; } if(onGround) { velocity.X *= groundDrag; velocity.Y = 0.0f; } else { velocity.X *= airDrag; velocity.Y += gravityAcceleration; } velocity.Y = MathHelper.Clamp(velocity.Y, -maxFallSpeed, maxFallSpeed); velocity.X = MathHelper.Clamp(velocity.X, -maxMoveSpeed, maxMoveSpeed); position += velocity * (float)gameTime.ElapsedGameTime.TotalSeconds; position = new Vector2((float)Math.Round(position.X), (float)Math.Round(position.Y)); if(Math.Round(velocity.X) != 0.0f) { HandleCollisions2(Direction.Horizontal); } if(Math.Round(velocity.Y) != 0.0f) { HandleCollisions2(Direction.Vertical); } } private void HandleCollisions2(Direction direction) { int topTile = (int)Math.Floor((float)Bounds.Top / Tile.PixelTileSize); int bottomTile = (int)Math.Ceiling((float)Bounds.Bottom / Tile.PixelTileSize) - 1; int leftTile = (int)Math.Floor((float)Bounds.Left / Tile.PixelTileSize); int rightTile = (int)Math.Ceiling((float)Bounds.Right / Tile.PixelTileSize) - 1; for(int x = leftTile; x <= rightTile; x++) { for(int y = topTile; y <= bottomTile; y++) { Rectangle tileBounds = new Rectangle(x * Tile.PixelTileSize, y * Tile.PixelTileSize, Tile.PixelTileSize, Tile.PixelTileSize); Vector2 depth; if(Tile.IsSolid(x, y) && Intersects(tileBounds, direction, out depth)) { if(direction == Direction.Horizontal) { position.X += depth.X; } else { onGround = true; isPressable = true; airTime = 0.0f; position.Y += depth.Y; } } } } } From the code you can see when velocity.X is not equal to zero the HandleCollisions() Method is called along the horizontal axis and likewise for the vertical axis. When velocity.X is not equal to zero and velocity.Y is equal to zero it works fine. When velocity.Y is not equal to zero and velocity.X is equal to zero everything also works fine. However when both axis are not equal to zero that's when it doesn't work and I don't know why. I basically teleport to the left side of a tile when both axis are not equal to zero and there is a air block next to me. Hopefully someone can see the problem with this because I sure don't as far as I'm aware nothing has even changed from what I'm doing to what the linked post's solution is doing. Thanks.

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How do I run my XBOX XNA game without a network connection?

- by Hugh

I need to demo my XBOX XNA game in college. The college doesn't allow this type of device to connect to the network. I deployed my game to the Xbox and it is sitting in the games list along with my other games. It runs fine with a network connection but when its offline it comes up with an error message saying its needs a connection to run the game. This makes no sense, the game is deployed on the Xbox memory, it must be some security policy or something! Is there any way around this? The demo is on monday!

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Pathfinding in multi goal, multi agent environment

- by Rohan Agrawal

I have an environment in which I have multiple agents (a), multiple goals (g) and obstacles (o). . . . a o . . . . . . . o . g . . a . . . . . . . . . . o . . . . o o o o . g . . o . . . . . . . o . . . . o . . . . o o o o a What would an appropriate algorithm for pathfinding in this environment? The only thing I can think of right now, is to Run a separate version of A* for each goal separately, but i don't think that's very efficient.

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Deserialize inherited classes into the same list in XNA

- by M0rgenstern

I am writing a Gui for a game (for what else ...). Therefor I wrote a class GuiElement which has some serializeable fields. From this class I deflect a Class "Button" which has one serializeable field more. Furthermore, I have a Class GuiWindow, which is as well deflected from "GuiElement". An Object of this Class has a Field "HandledElements" of the type "List". To know the layout of the Menues, I use XML-Files, which look like that (for example): <?xml version="1.0" encoding="utf-8" ?> <XnaContent xmlns:Generic="System.Collections.Generic"> <Asset Type="System.Collections.Generic.List[GUI.GuiWindow]"> <Item> <Position>0 0</Position> <AlternativeImagePath></AlternativeImagePath> <IsActive>true</IsActive> <Name>MainMenu</Name> <HandledElements> <Item> <Position>100 100</Position> <AlternativeImagePath></AlternativeImagePath> <IsActive>true</IsActive> <Name>Optionen</Name> <Caption>Optionen</Caption> </Item> </HandledElements> </Item> <Item> <Position>0 0</Position> <AlternativeImagePath></AlternativeImagePath> <IsActive>false</IsActive> <Name>Options</Name> <HandledElements> </HandledElements> </Item> </Asset> </XnaContent> As you can see, the first window has in its "HandledElements" List an Item with the Field . This is a field which only a Button has. The Problem is now: I can't deserialize this XML file, because GuiElement does not have this Field, it only has the few fields above. I thought it would know automatically which Class to use,but it doesn't. Do I really have to give my windows a list for each child class of GuiElement? Or can I do another workaround?

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Generating geometry when using VBO

- by onedayitwillmake

Currently I am working on a project in which I generate geometry based on the players movement. A glorified very long trail, composed of quads. I am doing this by storing a STD::Vector, and removing the oldest verticies once enough exist, and then calling glDrawArrays. I am interested in switching to a shader based model, usually examples I see the VBO is generated at start and then that's basically it. What is the best route to go about creating geometry in real time, using shader / VBO approach

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How to choose cell to put entity in in an uniform grid used for broad phase collision detection?

- by nathan

I'm trying to implement the broad phase of my collision detection algorithm. My game is an arcade game with lot of moving entities in an open space with relatively equivalent sizes. Regarding the above specifications, i decided to use an uniform grid for space partitioning. The problem i have right know is how to efficiently choose in which cells an entity should be added. ATM i'm doing something like this: for (int x = 0; x < gridSize; x++) { for (int y = 0; y < gridSize; y++) { GridCell cell = grid[x][y]; cell.clear(); //remove the previously added entities for (int i = 0; i < entities.size(); i++) { Entity e = entities.get(i); if (cell.isEntityOverlap(e)) { cell.add(e); } } } } The isEntityOverlap is a simple method i added my GridCell class. public boolean isEntityOverlap(Shape s) { return cellArea.intersects(s); } Where cellArea is a Rectangle. cellArea = new Rectangle(x, y, CollisionGrid.CELL_SIZE, CollisionGrid.CELL_SIZE); It works but it's damn slow. What would be a fast way to know all the cells an entity overlaps? Note: by "it works" i mean, the entities are contained in the good cells over the time after movements etc.

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Why do the order of uniforms gets changed by the compiler?

- by Aybe

I have the following shader, everything works fine when setting the value of one of the matrices but I've discovered that getting a value back is incorrect for View and Projection, they are in reverse order. #version 430 precision highp float; layout (location = 0) uniform mat4 Model; layout (location = 1) uniform mat4 View; layout (location = 2) uniform mat4 Projection; layout (location = 0) in vec3 in_position; layout (location = 1) in vec4 in_color; out vec4 out_color; void main(void) { gl_Position = Projection * View * Model * vec4(in_position, 1.0); out_color = in_color; } When querying their location they are effectively reversed, I did a small test by renaming View to Piew which puts it before Projection if sorted alphabetically and the order is correct. Now if I do remove layout (location = ...) from the uniforms, the problem disappears !? I am starting to think that this is a driver bug as explained in the wiki. Do you know why the order of the uniforms is changed whenever the shader is compiled ? (using an AMD HD7850)

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