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  • Collision Detection for a 2D RPG

    - by PHMitrious
    First of all, I have done some research on this topic before asking, and I'm asking this question as a mean to get some opinions on this topic, so I don't make a decision only on my own, but taking into account other people's experience as well. I'm starting a 2D online RPG project. I am using SFML for graphics and input and I'm creating a basic game structure and all for the game, creating modules for each part of the game. Well, let me get to the point I just wanted to give you guys some context. I want to decide on how I'm going to work with collision detection. Well I'm kinda going to work on maps with a tile map divided in layers (as usual) and add an extra 2 layers - not exactly in the map - for objects. So I'll have collisions between objects and agents (players - npcs - monsters - spells etc) and agents and tiles. The seconds one can be easily solved the first one need a little bit of work. I considered both creating a basic collision test engine using polygons and a quadtree to diminish tests since I'm going to be working with big maps with lots of objects - creating both a physical and graphical world representation. And I also considered using a physics engine like Box2D for collision tests. I think the first approach would take more work on my part but the second one would have the overhead of using a whole physics engine for just collision detection and no physics. What do you guys think ?

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  • Architecture of an action multiplayer game from scratch

    - by lcf
    Not sure whether it's a good place to ask (do point me to a better one if it's not), but since what we're developing is a game - here it goes. So this is a "real-time" action multiplayer game. I have familiarized myself with concepts like lag compensation, view interpolation, input prediction and pretty much everything that I need for this. I have also prepared a set of prototypes to confirm that I understood everything correctly. My question is about the situation when game engine must be rewind to the past to find out whether there was a "hit" (sometimes it may involve the whole 'recomputation' of the world from that moment in the past up to the present moment. I already have a piece of code that does it, but it's not as neat as I need it to be. The domain logic of the app (the physics of the game) must be separated from the presentation (render) and infrastructure tools (e.g. the remote server interaction specifics). How do I organize all this? :) Is there any worthy implementation with open sources I can take a look at? What I'm thinking is something like this: -> Render / User Input -> Game Engine (this is the so called service layer) -> Processing User Commands & Remote Server -> Domain (Physics) How would you add into this scheme the concept of "ticks" or "interactions" with the possibility to rewind and recalculate "the game"? Remember, I cannot change the Domain/Physics but only the Game Engine. Should I store an array of "World's States"? Should they be just some representations of the world, optimized for this purpose somehow (how?) or should they be actual instances of the world (i.e. including behavior and all that). Has anybody had similar experience? (never worked on a game before if that matters)

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  • LibGDX Box2D Body and Sprite AND DebugRenderer out of sync

    - by Free Lancer
    I am having a couple issues with Box2D bodies. I have a GameObject holding a Sprite and Body. I use a ShapeRenderer to draw an outline of the Body's and Sprite's bounding boxes. I also added a Box2DDebugRenderer to make sure everything's lining up properly. My problem is the Sprite and Body at first overlap perfectly, but as I turn the Body moves a bit off the sprite then comes back when the Car is facing either North or South. Here's an image of what I mean: (Not sure what that line is, first time to show up) BLUE is the Body, RED is the Sprite, PURPLE is the Box2DDebugRenderer. Also, you probably noticed a purple square in the top right corner. Well that's the Car drawn by the Box2D Debug Renderer. I thought it might be the camera but I've been playing with the Cameras for hours and nothing seems to work. All give me weird results. Here's my code: Screen: public void show() { // --------------------- SETUP ALL THE CAMERA STUFF ------------------------------ // battleStage = new Stage( 720, 480, false ); // Setup the camera. In Box2D we operate on a meter scale, pixels won't do it. So we use // an Orthographic camera with a Viewport of 24 meters in width and 16 meters in height. battleStage.setCamera( new OrthographicCamera( CAM_METER_WIDTH, CAM_METER_HEIGHT ) ); battleStage.getCamera().position.set( CAM_METER_WIDTH / 2, CAM_METER_HEIGHT / 2, 0 ); // The Box2D Debug Renderer will handle rendering all physics objects for debugging debugger = new Box2DDebugRenderer( true, true, true, true ); //debugCam = new OrthographicCamera( CAM_METER_WIDTH, CAM_METER_HEIGHT ); } public void render(float delta) { // Update the Physics World, use 1/45 for something around 45 Frames/Second for mobile devices physicsWorld.step( 1/45.0f, 8, 3 ); // 1/45 for devices // Set the Camera matrices and clear the screen Gdx.gl.glClear(GL10.GL_COLOR_BUFFER_BIT); battleStage.getCamera().update(); // Draw game objects here battleStage.act(delta); battleStage.draw(); // Again update the Camera matrices and call the debug renderer debugCam.update(); debugger.render( physicsWorld, debugCam.combined); // Vehicle handles its own interaction with the HUD // update all Actors movements in the game Stage hudStage.act( delta ); // Draw each Actor onto the Scene at their new positions hudStage.draw(); } Car: (extends Actor) public Car( Texture texture, float posX, float posY, World world ) { super( "Car" ); mSprite = new Sprite( texture ); mSprite.setSize( WIDTH * Consts.PIXEL_METER_RATIO, HEIGHT * Consts.PIXEL_METER_RATIO ); mSprite.setOrigin( mSprite.getWidth()/2, mSprite.getHeight()/2); // set the origin to be at the center of the body mSprite.setPosition( posX * Consts.PIXEL_METER_RATIO, posY * Consts.PIXEL_METER_RATIO ); // place the car in the center of the game map FixtureDef carFixtureDef = new FixtureDef(); mBody = Physics.createBoxBody( BodyType.DynamicBody, carFixtureDef, mSprite ); } public void draw() { mSprite.setPosition( mBody.getPosition().x * Consts.PIXEL_METER_RATIO, mBody.getPosition().y * Consts.PIXEL_METER_RATIO ); mSprite.setRotation( MathUtils.radiansToDegrees * mBody.getAngle() ); // draw the sprite mSprite.draw( batch ); } Physics: (Create the Body) public static Body createBoxBody( final BodyType pBodyType, final FixtureDef pFixtureDef, Sprite pSprite ) { float pRotation = 0; float pWidth = pSprite.getWidth(); float pHeight = pSprite.getHeight(); final BodyDef boxBodyDef = new BodyDef(); boxBodyDef.type = pBodyType; boxBodyDef.position.x = pSprite.getX() / Consts.PIXEL_METER_RATIO; boxBodyDef.position.y = pSprite.getY() / Consts.PIXEL_METER_RATIO; // Temporary Box shape of the Body final PolygonShape boxPoly = new PolygonShape(); final float halfWidth = pWidth * 0.5f / Consts.PIXEL_METER_RATIO; final float halfHeight = pHeight * 0.5f / Consts.PIXEL_METER_RATIO; boxPoly.setAsBox( halfWidth, halfHeight ); // set the anchor point to be the center of the sprite pFixtureDef.shape = boxPoly; final Body boxBody = BattleScreen.getPhysicsWorld().createBody(boxBodyDef); boxBody.createFixture(pFixtureDef); } Sorry for all the code and long description but it's hard to pin down what exactly might be causing the problem.

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  • Making AI jump on a spot effectively

    - by Pasquale Sada
    How to calculate, in 3D environment, the closest point, from which an AI character can jump onto a platform? Setup I have an initial velocity V(Vx,Vy,VZ) and a spot where the character stands still at S(Sx,Sy,Sz). What I'm trying to achieve is a successful jump on a spot E(Ex,Ey,Ez) where you have clicked on(only lower or higher spot, because I've in place a simple steering behavior for even terrains). There are no obstacles around. I've implemented a formula that can make him jump in a precise way on a spot but you need to declare an angle: the problem arise when the selected spot is straight above your head. It' pretty lame that the char hang there and can reach a thing that is 1cm above is head. I'll share the code I'm using: Vector3 dir = target - transform.position; // get target direction float h = dir.y; // get height difference dir.y = 0; // retain only the horizontal direction float dist = dir.magnitude ; // get horizontal distance float a = angle * Mathf.Deg2Rad; // convert angle to radians dir.y = dist * Mathf.Tan(a); // set dir to the elevation angle dist += h / Mathf.Tan(a); // correct for small height differences // calculate the velocity magnitude float vel = Mathf.Sqrt(dist * Physics.gravity.magnitude / Mathf.Sin(2 *a)); return vel * dir.normalized; Ended up using the lowest angle (20 degree) and checking for collision on the trajectory. If found any increase the angle. Here some code (to improve the code maybe must stop the check at the highest point of the curve): Vector3 BallisticVel(Vector3 target, float angle) { Vector3 dir = target - transform.position; // get target direction float h = dir.y; // get height difference dir.y = 0; // retain only the horizontal direction float dist = dir.magnitude ; // get horizontal distance float a = angle * Mathf.Deg2Rad; // convert angle to radians dir.y = dist * Mathf.Tan(a); // set dir to the elevation angle dist += h / Mathf.Tan(a); // correct for small height differences // calculate the velocity magnitude float vel = Mathf.Sqrt(dist * Physics.gravity.magnitude / Mathf.Sin(2 * a)); return vel * dir.normalized; } Vector3 TrajectoryPoint(Vector3 startingPosition, Vector3 startingVelocity, float n ) { float t = 1/60 ; // seconds per time step Vector3 stepVelocity = t * startingVelocity; // m/s Vector3 stepGravity = t * t * Physics.gravity; // m/s/s return startingPosition + n * stepVelocity + 0.5f * (n*n+n) * stepGravity; } bool CheckTrajectory(Vector3 startingPosition,Vector3 target, float angle_jump) { Debug.Log("checking"); if(angle_jump < 80f) { Debug.Log("if"); Vector3 startingVelocity = BallisticVel(target, angle_jump); for (int i = 0; i < 180; i++) { //Debug.Log(i); Vector3 trajectoryPosition = TrajectoryPoint( startingPosition, startingVelocity, i ); if(Physics.Raycast(trajectoryPosition,Vector3.forward,safeDistance)) { angle_jump += 10; break; // restart loop with the new angle } else continue; } return true; JumpVelocity = BallisticVel(target, angle_jump); } return false; }

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  • Is there a standard way to store 3D meshes to easily communicate between libraries?

    - by awiebe
    In a 3D game lots of different systems need to know about geometry data, however the only way they seem to be able to agree to on in representing it by an array of triangles. Can anyone recommend a good geometry manipulation library that will allow me to easily integrate the drawing library(OpenGL), the physics engine(Bullet), Serialization(Several 3D file formats) and my own code(objective-c++). Focus on the a representation between the drawing library and the physics engine. Also if the library can triangulate a mesh definition that would be very helpful. My code can work around what exists already.

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  • Do 2D games have a future? [closed]

    - by Griffin
    I'm currently working on a 2D soft-body physics engine (since none exist right now -_-), but I'm worried that there's no point to spending what will most likely be years on it. Although I love working on it, I doubt such an engine would get any income considering anyone willing to pay money for the library will likely to be working in 3D. Do 2D games have any sort of future in the game industry? Should I just drop my engine and find something meaningful to work on? Bonus: I've been trying to think of a unique way to implement my physics engine in a 2d game by looking at games that are multiple dimensions, but still in 2d perspective like Paper Mario. Any ideas?

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  • How to make an arc'd, but not mario-like jump in python, pygame [duplicate]

    - by PythonInProgress
    This question already has an answer here: Arc'd jumping method? 2 answers Analysis of Mario game Physics [closed] 6 answers I have looked at many, many questions similar to this, and cannot find a simple answer that includes the needed code. What i am trying to do is raise the y value of a square for a certain amount of time, then raise it a bit more, then a bit more, then lower it twice. I cant figure out how to use acceleration/friction, and might want to do that too. P.S. - can someone tell me if i should post this on stackoverflow or not? Thanks all! Edit: What i am looking for is not mario-like physics, but a simple equation that can be used to increase then decrease height over the time over a few seconds.

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  • Units in tile world

    - by Vilzow
    I've started to make a 2D sidescroller, the camera and world rendering works as I expect, but now comes the physics part of world. What I need is that one tile in x direction (or y direction) should correspond to 1 meter. Since I have a variable time step (android mobile game), I can't figure it out, since the timing and velocity always will be dependent of the device. So, is there any good way to make one tile to correspond 1 meter? This would be good, otherwise the physics implementation would later be weird.

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  • Lag compensation with networked 2D games

    - by Milo
    I want to make a 2D game that is basically a physics driven sandbox / activity game. There is something I really do not understand though. From research, it seems like updates from the server should only be about every 100ms. I can see how this works for a player since they can just concurrently simulate physics and do lag compensation through interpolation. What I do not understand is how this works for updates from other players. If clients only get notified of player positions every 100ms, I do not see how that works because a lot can happen in 100ms. The player could have changed direction twice or so in that time. I was wondering if anyone would have some insight on this issue. Basically how does this work for shooting and stuff like that? Thanks

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  • Bullet physics in python and pygame

    - by Pomg
    I am programming a 2D sidescroller in python and pygame and am having trouble making a bullet go farther than just farther than the player. The bullet travels straight to the ground after i fire it. How, in python code using pygame do I make the bullet go farther. If you need code, here is the method that handles the bullet firing: self.xv += math.sin(math.radians(self.angle)) * self.attrs['speed'] self.yv += math.cos(math.radians(self.angle)) * self.attrs['speed'] self.rect.left += self.xv self.rect.top += self.yv

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  • Car-like Physics - Basic Maths to Simulate Steering

    - by Reanimation
    As my program stands I have a cube which I can control using keyboard input. I can make it move left, right, up, down, back, fourth along the axis only. I can also rotate the cube either left or right; all the translations and rotations are implemented using glm. if (keys[VK_LEFT]) //move cube along xAxis negative { globalPos.x -= moveCube; keys[VK_RIGHT] = false; } if (keys[VK_RIGHT]) //move cube along xAxis positive { globalPos.x += moveCube; keys[VK_LEFT] = false; } if (keys[VK_UP]) //move cube along yAxis positive { globalPos.y += moveCube; keys[VK_DOWN] = false; } if (keys[VK_DOWN]) //move cube along yAxis negative { globalPos.y -= moveCube; keys[VK_UP] = false; } if (FORWARD) //W - move cube along zAxis positive { globalPos.z += moveCube; BACKWARD = false; } if (BACKWARD) //S- move cube along zAxis negative { globalPos.z -= moveCube; FORWARD = false; } if (ROT_LEFT) //rotate cube left { rotX +=0.01f; ROT_LEFT = false; } if (ROT_RIGHT) //rotate cube right { rotX -=0.01f; ROT_RIGHT = false; } I render the cube using this function which handles the shader and position on screen: void renderMovingCube(){ glUseProgram(myShader.handle()); GLuint matrixLoc4MovingCube = glGetUniformLocation(myShader.handle(), "ProjectionMatrix"); glUniformMatrix4fv(matrixLoc4MovingCube, 1, GL_FALSE, &ProjectionMatrix[0][0]); glm::mat4 viewMatrixMovingCube; viewMatrixMovingCube = glm::lookAt(camOrigin,camLookingAt,camNormalXYZ); ModelViewMatrix = glm::translate(viewMatrixMovingCube,globalPos); ModelViewMatrix = glm::rotate(ModelViewMatrix,rotX, glm::vec3(0,1,0)); //manually rotate glUniformMatrix4fv(glGetUniformLocation(myShader.handle(), "ModelViewMatrix"), 1, GL_FALSE, &ModelViewMatrix[0][0]); movingCube.render(); glUseProgram(0); } The glm::lookAt function always points to the screens centre (0,0,0). The globalPos is a glm::vec3 globalPos(0,0,0); so when the program executes, renders the cube in the centre of the screens viewing matrix; the keyboard inputs above adjust the globalPos of the moving cube. The glm::rotate is the function used to rotate manually. My question is, how can I make the cube go forwards depending on what direction the cube is facing.... ie, once I've rotated the cube a few degrees using glm, the forwards direction, relative to the cube, is no longer on the z-Axis... how can I store the forwards direction and then use that to navigate forwards no matter what way it is facing? (either using vectors that can be applied to my code or some handy maths). Thanks.

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  • Physics like asteroides

    - by user2933016
    I try to make a ship that has the physic properties like asteroides. I have this for now(All in Java): Ship.class public class Ship { public static final float sMaxHealth = 0.1F; public static final float sMaxMoveVelocity = 5.0F; public static final float sMaxAngleVelocity = 20.0F; public static final float sRadius = 1.0F; public static final float sMoveDeceleration = 10.0F; public static final float sMoveAcceleration = 2.0F; public static final float sAngleDeceleration = 15.0F; public static final float sAngleAcceleration = 20.0F; private float mHealth; private float mXVelocity; private float mYVelocity; private float mAngleVelocity; private float mX; private float mY; private float mAngle; } (I let the getter and setter away for now) Controller code // Player input if(Gdx.input.isKeyPressed(Keys.UP)) { mPlayer.setXVelocity(mPlayer.getXVelocity() + (float) Math.cos(mPlayer.getAngle()) * Ship.sMoveAcceleration); mPlayer.setYVelocity(mPlayer.getYVelocity() + (float) Math.sin(mPlayer.getAngle()) * Ship.sMoveAcceleration); } if(Gdx.input.isKeyPressed(Keys.LEFT)) { mPlayer.setAngleVelocity(mPlayer.getAngleVelocity() + Ship.sAngleAcceleration * pDeltaTime); } if(Gdx.input.isKeyPressed(Keys.RIGHT)) { mPlayer.setAngleVelocity(mPlayer.getAngleVelocity() - Ship.sAngleAcceleration * pDeltaTime); } // X velocity if(mPlayer.getXVelocity() < 0) { if(-mPlayer.getXVelocity() > Ship.sMaxMoveVelocity) { mPlayer.setXVelocity(-Ship.sMaxMoveVelocity); } mPlayer.setXVelocity(mPlayer.getXVelocity() + Ship.sMoveDeceleration * pDeltaTime); if(mPlayer.getXVelocity() > 0) { mPlayer.setXVelocity(0); } } else if(mPlayer.getXVelocity() > 0) { if(mPlayer.getXVelocity() > Ship.sMaxMoveVelocity) { mPlayer.setXVelocity(Ship.sMaxMoveVelocity); } mPlayer.setXVelocity(mPlayer.getXVelocity() - Ship.sMoveDeceleration * pDeltaTime); if(mPlayer.getXVelocity() < 0) { mPlayer.setXVelocity(0); } } // Y velocity if(mPlayer.getYVelocity() < 0) { if(-mPlayer.getYVelocity() > Ship.sMaxMoveVelocity) { mPlayer.setYVelocity(-Ship.sMaxMoveVelocity); } mPlayer.setYVelocity(mPlayer.getYVelocity() + Ship.sMoveDeceleration * pDeltaTime); if(mPlayer.getYVelocity() > 0) { mPlayer.setYVelocity(0); } } else if(mPlayer.getYVelocity() > 0) { if(mPlayer.getYVelocity() > Ship.sMaxMoveVelocity) { mPlayer.setYVelocity(Ship.sMaxMoveVelocity); } mPlayer.setYVelocity(mPlayer.getYVelocity() - Ship.sMoveDeceleration * pDeltaTime); if(mPlayer.getYVelocity() < 0) { mPlayer.setYVelocity(0); } } // Angle velocity if(mPlayer.getAngleVelocity() < 0) { if(-mPlayer.getAngleVelocity() > Ship.sMaxAngleVelocity) { mPlayer.setAngleVelocity(-Ship.sMaxAngleVelocity); } mPlayer.setAngleVelocity(mPlayer.getAngleVelocity() + Ship.sAngleDeceleration * pDeltaTime); if(mPlayer.getAngleVelocity() > 0) { mPlayer.setAngleVelocity(0); } } else if(mPlayer.getAngleVelocity() > 0) { if(mPlayer.getAngleVelocity() > Ship.sMaxAngleVelocity) { mPlayer.setAngleVelocity(Ship.sMaxAngleVelocity); } mPlayer.setAngleVelocity(mPlayer.getAngleVelocity() - Ship.sAngleDeceleration * pDeltaTime); if(mPlayer.getAngleVelocity() < 0) { mPlayer.setAngleVelocity(0); } } mPlayer.setX(mPlayer.getX() + mPlayer.getXVelocity() * pDeltaTime); mPlayer.setY(mPlayer.getY() + mPlayer.getYVelocity() * pDeltaTime); mPlayer.setAngle(mPlayer.getAngle() + mPlayer.getAngleVelocity() * pDeltaTime); Why the ship does not behave like in asteroides ? What do I wrong?

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  • Model a chain with different elements in Unity 3D

    - by Alex
    I have to model, in unity 3D, a chain that is composed of various elements. some flexible, some rigid. The idea is to realize a human-chain where each person is linked to the other by their hands. I've not tried to implement it yet as i've no idea on what could be a good way to do it. In the game i've to manage a lot of chains of people... maybe also 100 chains composed of 11-15 people. The chain will be pretty simple and there won't be much interaction... Probabily some animation of the people one at time for each chain and some physic reaction (for example pushing a people in a chain should slightle flex the chain) the very problem of this work is that in the chain each object is composed by flexible parts (arms) and rigid parts (the body) and that the connection should remain firm... just like when people handshake... hands are firm and are the wrists to move. i can use C4D to model the meshes. i know this number may cause performance problems, but it's also true i will use low-poly versions of human. (for the real it won't be human, but very simple toonish characters that have harms and legs). So actually i'm trying to find a way to manage this in a way it can work, the performance will be a later problem that i can solve. If there is not a fast 'best-practiced' solution and you have any link/guide/doc that could help me in finding a way to realize this is, it would be very appreciated anyway if you post it. thanks

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  • Procedual level generation for a platformer game (tilebased) using player physics

    - by Notbad
    I have been searching for information about how to build a 2d world generator (tilebased) for a platformer game I am developing. The levels should look like dungeons with a ceiling and a floor and they will have a high probability of being just made of horizontal rooms but sometimes they can have exits to a top/down room. Here is an example of what I would like to achieve. I'm refering only to the caves part. I know level design won't be that great when generated but I think it is possible to have something good enough for people to enjoy the procedural maps (Note: Supermetrod Spoiler!): http://www.snesmaps.com/maps/SuperMetroid/SuperMetroidMapNorfair.html Well, after spending some time thinking about this I have some ideas to create the maps that I would like to share with you: 1) I have read about celular automatas and I would like to use them to carve the rooms but instead of carving just a tile at once I would like to carve full columns of tiles. Of course this carving system will have some restrictions like how many tiles must be left for the roof and the ceiling, etc... This way I could get much cleaner rooms than using the ussual automata. 2) I want some branching into the rooms. It will have little probability to happen but I definitely want it. Thinking about carving I came to the conclusion that I could be using some sort of path creation algorithm that the carving system would follow to create a path in the rooms. This could be more noticiable if we make the carving system to carve columns with the height of a corridor or with the height of a wide room (this will be added to the system as a param). This way at some point I could spawn a new automa beside the main one to create braches. This new automata should play side by side with the first one to create dead ends, islands (both paths created by the automatas meet at some point or lead to the same room. It would be too long to explain here all the tests I have done, etc... just will try to summarize the problems to see if anyone could bring some light to solve them (I don't mind sharing my successes but I think they aren't too relevant): 1) Zone reachability: How can I make sure that the player will be able to reach all zones I created (mainly when branches happen or vertical rooms are created). When branches are created I have to make sure that there will be a way to get onto the new created branch. I mean a bifurcation that the player could follow. Player will follow the main path or jump to a platform to get onto the other way). On the other hand if an island is created by the meeting of both branches I need to make sure the player will be able to get onto the island too. 2) When a branch is created and corridors are generated for each branch how can I make then both merge or repel to create an island or just make them separated corridors. 3) When I create a branch and an island is created becasue both corridors merge at somepoint or they lead to the same room, is there any way to detect this and randomize where to create the needed platforms to get onto the created isle? This platforms could be created at the start of the island or at the end. I guess part of the problem could be solved using some sort of graph following the created paths but I'm a bit lost in this sea of precedural content creation :). On the other hand I don't expect a solution to the problem but some information to get me moving forward again. Thanks in advance.

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  • Which jar has JBox2d's p5 package

    - by Brantley Blanchard
    Using eclipse, I'm trying to write a simple hello world program in processing that simply draws a rectangle on the screen then has gravity drop it as seen in this Tutorial. The problem is that when I try to import the p5 package, it's not resolving so I can't declare my Physics object. I tried two things. Download the zip, unzip it, then import the 3 jars (library, serialization, & testbed) a. import org.jbox2d.p5.*; doesn't resolve but the others do b. Physics physics; doesn't resolve Download the older standalone testbed jar then import it a. Physics physics; doesn't resolve; Here is basically where I'm starting import org.jbox2d.util.nonconvex.*; import org.jbox2d.dynamics.contacts.*; import org.jbox2d.testbed.*; import org.jbox2d.collision.*; import org.jbox2d.common.*; import org.jbox2d.dynamics.joints.*; import org.jbox2d.p5.*; import org.jbox2d.dynamics.*; import processing.core.PApplet; public class MyFirstJBox2d extends PApplet { Physics physics; public void setup() { size(640,480); frameRate(60); initScene(); } public void draw() { background(0); if (keyPressed) { //Reset everything physics.destroy(); initScene(); } } public void initScene() { physics = new Physics(this, width, height); physics.setDensity(1.0f); physics.createRect(300,200,340,300); } }

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  • Bullet Physics, when to choose which DynamicsWorld?

    - by Sqeaky
    I have a few general questions about the bullet physics library. Here is my current understanding in a nutshell: btDiscreteDynamicsWorld - Simplest physics world, only handles rigid bodies, maybe it has better performance. btSoftRigidDynamicsWorld - The only physics world that can work with large jello moulds btContinuousDynamicsWorld - If you have really fast objects this will prevent them from prenetrating each other or flying through each other, but is otherwise like a btDiscreteDynamicsWorld. Is my understanding of the btDiscreetDynamicsWorld, btContinuousDynamicsWorld and btSoftRigidDynamicsWorld classes in terms of functionality, purpose, and performance correct? Why does the user manual recommend the btDiscreteDynamicsWorld class? btSoftRigidDynamicsWorld appears to be the only world that can handle soft bodies, so what if we wanted Continuous Physics integration and Soft bodies? How fast is fast enough to consider using a btContinuousDynamicsWorld, and what are the drawbacks of using one? Edit: My Buddy Mako also posted this question on The Bullet forums: http://www.bulletphysics.org/Bullet/phpBB3/viewtopic.php?f=9&t=4863

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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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  • Collision detection in 3D space

    - by dreta
    I've got to write, what can be summed up as, a compelte 3D game from scratch this semester. Up untill now i have only programmed 2D games in my spare time, the transition doesn't seem tough, the game's simple. The only issue i have is collision detection. The only thing i could find was AABB, bounding spheres or recommendations of various physics engines. I have to program a submarine that's going to be moving freely inside of a cave system, AFAIK i can't use physics libraries, so none of the above solves my problem. Up untill now i was using SAT for my collision detection. Are there any similar, great algorithms, but crafted for 3D collision? I'm not talking about octrees, or other optimalizations, i'm talking about direct collision detection of one set of 3D polygons with annother set of 3D polygons. I thought about using SAT twice, project the mesh from the top and the side, but then it seems so hard to even divide 3D space into convex shapes. Also that seems like far too much computation even with octrees. How do proffessionals do it? Could somebody shed some light.

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  • I am looking to make a spaceship tilt as it corners but I cant get it to return

    - by bobthemac
    I am using the TL game engine I am not allowed to use a physics engine but I need to make the spaceship lean as it corners, I can make it lean but cannot make it return to its starting position. I have looked at implementing some kind of spring physics but I don't understand it. Here is my code so far if(myEngine->KeyHeld(Key_A)) { car->RotateY(carSteer * frameTime); if(carSteer >= -carMaxSteer) { carSteer -= carSteerIncrement; car->RotateLocalZ(-(carSteer * frameTime)); } } if(!myEngine->KeyHeld(Key_A)) { if(carSteer < 0) { carSteer = 0; } } if(myEngine->KeyHeld(Key_D)) { car->RotateY(carSteer * frameTime); if(carSteer <= carMaxSteer) { carSteer += carSteerIncrement; car->RotateLocalZ(-(carSteer * frameTime)); } } if(!myEngine->KeyHeld(Key_D)) { if(carSteer > 0) { carSteer = 0; } } All the functions I am calling are built into the engine and I did not write them. Any Help Would Be Appreciated Thanks.

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  • colliding btRigidBody objects behave strangely when moving slowly

    - by Piku
    I'm trying to use Bullet Physics in my iOS game. The engine appears to be correctly compiled in that the demos work fine. In my game I have the player's ship and some enemy ships. They're defined as btRigidBody objects and btCollisionObjects and I'm using btSphereShapes for collision. At 'fast' speeds, collisions appear to happen sensibly - things collide and nothing goes 'weird'. If the speeds are very slow though and the player's ship touches a non-moving object the collision happens, but then the player's ship moves at incredible speed over the next few frames and appears a long distance from where it collided - completely out of proportion to the speed it was moving before impact. To move the things around I'm using setLinearVelocity() each frame, ticking the physics engine, then using getMotionState() to update the rendering code I have. Part of the issue might be I don't quite understand how to set the correct mass or what the best speeds are to use for anything. I'm mostly sticking numbers in and seeing what happens. Should I be using Bullet in this way, and are there any guidelines for deciding on the mass of objects? (am I right in assuming that in collisions heavier objects will force lighter objects to move more)

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  • Opposite Force to Apply to a Collided Rigid Body?

    - by Milo
    I'm working on the physics for my GTA2-like game so I can learn more about game physics. The collision detection and resolution are working great. I'm now just unsure how to compute the force to apply to a body after it collides with a wall. My rigid body looks like this: /our simulation object class RigidBody extends Entity { //linear private Vector2D velocity = new Vector2D(); private Vector2D forces = new Vector2D(); private float mass; private Vector2D v = new Vector2D(); //angular private float angularVelocity; private float torque; private float inertia; //graphical private Vector2D halfSize = new Vector2D(); private Bitmap image; private Matrix mat = new Matrix(); private float[] Vector2Ds = new float[2]; private Vector2D tangent = new Vector2D(); private static Vector2D worldRelVec = new Vector2D(); private static Vector2D relWorldVec = new Vector2D(); private static Vector2D pointVelVec = new Vector2D(); private static Vector2D acceleration = new Vector2D(); public RigidBody() { //set these defaults so we don't get divide by zeros mass = 1.0f; inertia = 1.0f; setLayer(LAYER_OBJECTS); } protected void rectChanged() { if(getWorld() != null) { getWorld().updateDynamic(this); } } //intialize out parameters public void initialize(Vector2D halfSize, float mass, Bitmap bitmap) { //store physical parameters this.halfSize = halfSize; this.mass = mass; image = bitmap; inertia = (1.0f / 20.0f) * (halfSize.x * halfSize.x) * (halfSize.y * halfSize.y) * mass; RectF rect = new RectF(); float scalar = 10.0f; rect.left = (int)-halfSize.x * scalar; rect.top = (int)-halfSize.y * scalar; rect.right = rect.left + (int)(halfSize.x * 2.0f * scalar); rect.bottom = rect.top + (int)(halfSize.y * 2.0f * scalar); setRect(rect); } public void setLocation(Vector2D position, float angle) { getRect().set(position.x,position.y, getWidth(), getHeight(), angle); rectChanged(); } public Vector2D getPosition() { return getRect().getCenter(); } @Override public void update(float timeStep) { doUpdate(timeStep); } public void doUpdate(float timeStep) { //integrate physics //linear acceleration.x = forces.x / mass; acceleration.y = forces.y / mass; velocity.x += (acceleration.x * timeStep); velocity.y += (acceleration.y * timeStep); //velocity = Vector2D.add(velocity, Vector2D.scalarMultiply(acceleration, timeStep)); Vector2D c = getRect().getCenter(); v.x = getRect().getCenter().getX() + (velocity.x * timeStep); v.y = getRect().getCenter().getY() + (velocity.y * timeStep); setCenter(v.x, v.y); forces.x = 0; //clear forces forces.y = 0; //angular float angAcc = torque / inertia; angularVelocity += angAcc * timeStep; setAngle(getAngle() + angularVelocity * timeStep); torque = 0; //clear torque } //take a relative Vector2D and make it a world Vector2D public Vector2D relativeToWorld(Vector2D relative) { mat.reset(); Vector2Ds[0] = relative.x; Vector2Ds[1] = relative.y; mat.postRotate(JMath.radToDeg(getAngle())); mat.mapVectors(Vector2Ds); relWorldVec.x = Vector2Ds[0]; relWorldVec.y = Vector2Ds[1]; return relWorldVec; } //take a world Vector2D and make it a relative Vector2D public Vector2D worldToRelative(Vector2D world) { mat.reset(); Vector2Ds[0] = world.x; Vector2Ds[1] = world.y; mat.postRotate(JMath.radToDeg(-getAngle())); mat.mapVectors(Vector2Ds); worldRelVec.x = Vector2Ds[0]; worldRelVec.y = Vector2Ds[1]; return worldRelVec; } //velocity of a point on body public Vector2D pointVelocity(Vector2D worldOffset) { tangent.x = -worldOffset.y; tangent.y = worldOffset.x; pointVelVec.x = (tangent.x * angularVelocity) + velocity.x; pointVelVec.y = (tangent.y * angularVelocity) + velocity.y; return pointVelVec; } public void applyForce(Vector2D worldForce, Vector2D worldOffset) { //add linear force forces.x += worldForce.x; forces.y += worldForce.y; //add associated torque torque += Vector2D.cross(worldOffset, worldForce); } @Override public void draw( GraphicsContext c) { c.drawRotatedScaledBitmap(image, getPosition().x, getPosition().y, getWidth(), getHeight(), getAngle()); } public Vector2D getVelocity() { return velocity; } public void setVelocity(Vector2D velocity) { this.velocity = velocity; } } The way it is given force is by the applyForce method, this method considers angular torque. I'm just not sure how to come up with the vectors in the case where: RigidBody hits static entity RigidBody hits other RigidBody that may or may not be in motion. Would anyone know a way (without too complex math) that I could figure out the opposite force I need to apply to the car? I know the normal it is colliding with and how deep it collided. My main goal is so that say I hit a building from the side, well the car should not just stay there, it should slowly rotate out of it if I'm more than 45 degrees. Right now when I hit a wall I only change the velocity directly which does not consider angular force. Thanks!

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  • Friction not working for Vehicle in BulletPhysics

    - by Manmohan Bishnoi
    I am creating a vehicle using bullet-physics engine (v 2.82). I created a ground ( btBoxShape ), a box and a vehicle (following the demo). But friction between ground and vehicle wheels seems not working. As soon as the vehicle is placed in 3d world, it starts moving forward. START : Steering works for the vehicle, but engineForce and brakingForce does not work (i.e. I cannot speed-up or stop the vehicle) : I create physics world like this : void initPhysics() { broadphase = new btDbvtBroadphase(); collisionConfiguration = new btDefaultCollisionConfiguration(); dispatcher = new btCollisionDispatcher(collisionConfiguration); solver = new btSequentialImpulseConstraintSolver(); dynamicsWorld = new btDiscreteDynamicsWorld(dispatcher, broadphase, solver, collisionConfiguration); dynamicsWorld->setGravity(btVector3(0, -9.81, 0)); // Debug Drawer bulletDebugugger.setDebugMode(btIDebugDraw::DBG_DrawWireframe); dynamicsWorld->setDebugDrawer(&bulletDebugugger); //groundShape = new btStaticPlaneShape(btVector3(0, 1, 0), 1); groundShape = new btBoxShape(btVector3(50, 3, 50)); fallShape = new btBoxShape(btVector3(1, 1, 1)); // Orientation and Position of Ground groundMotionState = new btDefaultMotionState(btTransform(btQuaternion(0, 0, 0, 1), btVector3(0, -3, 0))); btRigidBody::btRigidBodyConstructionInfo groundRigidBodyCI(0, groundMotionState, groundShape, btVector3(0, 0, 0)); groundRigidBody = new btRigidBody(groundRigidBodyCI); dynamicsWorld->addRigidBody(groundRigidBody); /////////////////////////////////////////////////////////////////////// // Vehicle Setup /////////////////////////////////////////////////////////////////////// vehicleChassisShape = new btBoxShape(btVector3(1.f, 0.5f, 2.f)); vehicleBody = new btCompoundShape(); localTrans.setIdentity(); localTrans.setOrigin(btVector3(0, 1, 0)); vehicleBody->addChildShape(localTrans, vehicleChassisShape); localTrans.setOrigin(btVector3(3, 0.f, 0)); vehicleMotionState = new btDefaultMotionState(localTrans); //vehicleMotionState = new btDefaultMotionState(btTransform(btQuaternion(0, 0, 0, 1), btVector3(3, 0, 0))); btVector3 vehicleInertia(0, 0, 0); vehicleBody->calculateLocalInertia(vehicleMass, vehicleInertia); btRigidBody::btRigidBodyConstructionInfo vehicleRigidBodyCI(vehicleMass, vehicleMotionState, vehicleBody, vehicleInertia); vehicleRigidBody = new btRigidBody(vehicleRigidBodyCI); dynamicsWorld->addRigidBody(vehicleRigidBody); wheelShape = new btCylinderShapeX(btVector3(wheelWidth, wheelRadius, wheelRadius)); { vehicleRayCaster = new btDefaultVehicleRaycaster(dynamicsWorld); vehicle = new btRaycastVehicle(vehicleTuning, vehicleRigidBody, vehicleRayCaster); // never deactivate vehicle vehicleRigidBody->setActivationState(DISABLE_DEACTIVATION); dynamicsWorld->addVehicle(vehicle); float connectionHeight = 1.2f; bool isFrontWheel = true; vehicle->setCoordinateSystem(rightIndex, upIndex, forwardIndex); // 0, 1, 2 // add wheels // front left btVector3 connectionPointCS0(CUBE_HALF_EXTENT-(0.3*wheelWidth), connectionHeight, 2*CUBE_HALF_EXTENT-wheelRadius); vehicle->addWheel(connectionPointCS0, wheelDirectionCS0, wheelAxleCS, suspensionRestLength, wheelRadius, vehicleTuning, isFrontWheel); // front right connectionPointCS0 = btVector3(-CUBE_HALF_EXTENT+(0.3*wheelWidth), connectionHeight, 2*CUBE_HALF_EXTENT-wheelRadius); vehicle->addWheel(connectionPointCS0, wheelDirectionCS0, wheelAxleCS, suspensionRestLength, wheelRadius, vehicleTuning, isFrontWheel); isFrontWheel = false; // rear right connectionPointCS0 = btVector3(-CUBE_HALF_EXTENT+(0.3*wheelWidth), connectionHeight, -2*CUBE_HALF_EXTENT+wheelRadius); vehicle->addWheel(connectionPointCS0, wheelDirectionCS0, wheelAxleCS, suspensionRestLength, wheelRadius, vehicleTuning, isFrontWheel); // rear left connectionPointCS0 = btVector3(CUBE_HALF_EXTENT-(0.3*wheelWidth), connectionHeight, -2*CUBE_HALF_EXTENT+wheelRadius); vehicle->addWheel(connectionPointCS0, wheelDirectionCS0, wheelAxleCS, suspensionRestLength, wheelRadius, vehicleTuning, isFrontWheel); for (int i = 0; i < vehicle->getNumWheels(); i++) { btWheelInfo& wheel = vehicle->getWheelInfo(i); wheel.m_suspensionStiffness = suspensionStiffness; wheel.m_wheelsDampingRelaxation = suspensionDamping; wheel.m_wheelsDampingCompression = suspensionCompression; wheel.m_frictionSlip = wheelFriction; wheel.m_rollInfluence = rollInfluence; } } /////////////////////////////////////////////////////////////////////// // Orientation and Position of Falling body fallMotionState = new btDefaultMotionState(btTransform(btQuaternion(0, 0, 0, 1), btVector3(-1, 5, 0))); btScalar mass = 1; btVector3 fallInertia(0, 0, 0); fallShape->calculateLocalInertia(mass, fallInertia); btRigidBody::btRigidBodyConstructionInfo fallRigidBodyCI(mass, fallMotionState, fallShape, fallInertia); fallRigidBody = new btRigidBody(fallRigidBodyCI); dynamicsWorld->addRigidBody(fallRigidBody); } I step physics world like this : // does not work vehicle->applyEngineForce(maxEngineForce, WHEEL_REARLEFT); vehicle->applyEngineForce(maxEngineForce, WHEEL_REARRIGHT); // these also do not work vehicle->setBrake(gBreakingForce, WHEEL_REARLEFT); vehicle->setBrake(gBreakingForce, WHEEL_REARRIGHT); // this works vehicle->setSteeringValue(gVehicleSteering, WHEEL_FRONTLEFT); vehicle->setSteeringValue(gVehicleSteering, WHEEL_FRONTRIGHT); dynamicsWorld->stepSimulation(1 / 60.0f, 10); However If I apply brakingForce to all 4 wheels (i.e. including WHEEL_FRONTLEFT and WHEEL_FRONTRIGHT), then my vehicle stops, but keeps sliding/moving forward very very slowly. How do I fix this ?

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  • What if the Earth were Hollow? [Video]

    - by Asian Angel
    What would things be like if you dug a tunnel completely through the Earth for travel purposes or if our planet were hollow? Minute Physics takes a look at how things would be if either of these scenarios actually existed. What if the Earth were Hollow? [via Geeks are Sexy] How To Switch Webmail Providers Without Losing All Your Email How To Force Windows Applications to Use a Specific CPU HTG Explains: Is UPnP a Security Risk?

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  • How to calculate continuous motion with angular velocity in 2d

    - by Rulk
    I'm really new with physics. Maybe someone would be able to help me to solve the next problem: I need to calculate position of an agent on the plane(2D) in next time step where time step is large(20+ seconds) What I know about agent's motion: Initial Position Direction(normalised vector) Velocity(linear function from time ) - object always moves along it's direction Angular Velocity(linear function from time) Optional: External force direction External force (linear function from time) Running discreet simulation with t-0 is not an option.

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  • 2D Polygon Triangulation

    - by BleedObsidian
    I am creating a game engine using the JBox2D physics engine. It only allows you to create polygon fixtures up to 8 vertices, To create a body with more than 8 vertices, you need to create multiple fixtures for the body. My question is, How can I split the polygons a user creates into smaller polygons for JBox2D? Also, what topology should I use when splitting the polygons and why? (If JBox2D can have up to 8 vertices, why not split polygons into 8 per polygon)

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