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  • strange behavior in Box2D+LibGDX when applying impulse

    - by Z0lenDer
    I have been playing around with Box2D and LibGDX and have been using a sample code from DecisionTreeGames as the testing ground. Now I have a screen with four walls and a rectangle shape, lets call it a brick. When I use applyLinearImpulse to the brick, it starts bouncing right and left without any pattern and won't stop! I tried adding friction and increasing the density, but the behavior still remains the same. Here are some of the code that might be useful: method for applying the impulse: center = brick.getWorldCenter(); brick.applyLinearImpulse(20, 0, center.x, center.y); Defining the brick: brick_bodyDef.type = BodyType.DynamicBody; brick_bodyDef.position.set(pos); // brick is initially on the ground brick_bodyDef.angle = 0; brick_body = world.createBody(brick_bodyDef); brick_body.setBullet(true); brick_bodyShape.setAsBox(w,h); brick_fixtureDef.density = 0.9f; brick_fixtureDef.restitution = 1; brick_fixtureDef.shape = brick_bodyShape; brick_fixtureDef.friction=1; brick_body.createFixture(fixtureDef); Walls are defined the same only their bullet value is set to false I would really appreciate it if you could help me have a change this code to have a realistic behavior (i.e. when I apply impulse to the brick it should trip a few times and then stop completely).

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  • Strange behavior of RigidBody with gravity and impulse applied

    - by Heisenbug
    I'm doing some experiments trying to figure out how physics works in Unity. I created a cube mesh with a BoxCollider and a RigidBody. The cuve is laying on a mesh plane with a BoxCollider. I'm trying to update the object position applying a force on its RigidBody. Inside script FixedUpdate function I'm doing the following: public void FixedUpdate() { if (leftButtonPressed()) this.rigidbody.AddForce( this.transform.forward * this.forceStrength, ForceMode.Impulse); } Despite the object is aligned with the world axis and the force is applied along Z axis, it performs a quite big rotation movement around its y axis. Since I didn't modify the center of mass and the BoxCollider position and dimension, all values should be fine. Removing gravity and letting the object flying without touching the plane, the problem doesn't show. So I suppose it's related to the friction between objects, but I can't understand exactly which is the problem. Why this? What's my mistake? How can I fix this, or what's the right way to do such a moving an object on a plane through a force impulse?

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  • Show path of a body of where it should go after linear impulse is applied

    - by Farooq Arshed
    I am making a game with Andengine and Box2D. I have a dynamic body and I apply linear impulse on the body to move it around when the user have touched the screen. Now I want to show the path where the body will go when the user have touched. If you have played Angry Birds or Basket Ball Shoot or any other which have projectile motion with a path shown you will get my point. I want to show the white dots which are shown in those games.

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  • Matlab help: I am given a second order differential equation.I need to use matlab to find unit step response and impulse response?

    - by Cady Smith
    I have the second order differential equation d^2(y(t))/dt^2+ B1*d(y(t))/dt+ c1*y(t)=A1*x(t) t is in seconds and is greater than 0. A1, B1, C1 are constants that equal: A1= 3.8469x10^6 B1= 325.6907 C1= 3.8469x10^6 This system is linear, time-invariant, and casual. The system is called H1. I want to use Matlab to compute and plot the impulse response function h1(t) and the unit step response function g1(t) of this system.

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  • How to make a stack stable? Need help for an explicit resting contact scheme (2-dimensional)

    - by Register Sole
    Previously, I struggle with the sequential impulse-based method I developed. Thanks to jedediah referring me to this paper, I managed to rebuild the codes and implement the simultaneous impulse based method with Projected-Gauss-Seidel (PGS) iterative solver as described by Erin Catto (mentioned in the reference of the paper as [Catt05]). So here's how it currently is: The simulation handles 2-dimensional rotating convex polygons. Detection is using separating-axis test, with a SKIN, meaning closest points between two polygons is detected and determined if their distance is less than SKIN. To resolve collision, simultaneous impulse-based method is used. It is solved using iterative solver (PGS-solver) as in Erin Catto's paper. Error-correction is implemented using Baumgarte's stabilization (you can refer to either paper for this) using J V = beta/dt*overlap, J is the Jacobian for the constraints, V the matrix containing the velocities of the bodies, beta an error-correction parameter that is better be < 1, dt the time-step taken by the engine, and overlap, the overlap between the bodies (true overlap, so SKIN is ignored). However, it is still less stable than I expected :s I tried to stack hexagons (or squares, doesn't really matter), and even with only 4 to 5 of them, they would swing! Also note that I am not looking for a sleeping scheme. But I would settle if you have any explicit scheme to handle resting contacts. That said, I would be more than happy if you have a way of treating it generally (as continuous collision, instead of explicitly as a special state). Ideas I have tried: Using simultaneous position based error correction as described in the paper in section 5.3.2, turned out to be worse than the current scheme. If you want to know the parameters I used: Hexagons, side 50 (pixels) gravity 2400 (pixels/sec^2) time-step 1/60 (sec) beta 0.1 restitution 0 to 0.2 coeff. of friction 0.2 PGS iteration 10 initial separation 10 (pixels) mass 1 (unit is irrelevant for now, i modified velocity directly<-impulse method) inertia 1/1000 Thanks in advance! I really appreciate any help from you guys!! :) EDIT In response to Cholesky's comment about warm starting the solver and Baumgarte: Oh right, I forgot to mention! I do save the contact history and the impulse determined in this time step to be used as initial guess in the next time step. As for the Baumgarte, here's what actually happens in the code. Collision is detected when the bodies' closest distance is less than SKIN, meaning they are actually still separated. If at this moment, I used the PGS solver without Baumgarte, restitution of 0 alone would be able to stop the bodies, separated by a distance of ~SKIN, in mid-air! So this isn't right, I want to have the bodies touching each other. So I turn on the Baumgarte, where its role is actually to pull the bodies together! Weird I know, a scheme intended to push the body apart becomes useful for the reverse. Also, I found that if I increase the number of iteration to 100, stacks become much more stable, though the program becomes so slow. UPDATE Since the stack swings left and right, could it be something is wrong with my friction model? Current friction constraint: relative_tangential_velocity = 0

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  • Physics Engine [Collision Response, 2-dimensional] experts, help!! My stack is unstable!

    - by Register Sole
    Previously, I struggle with the sequential impulse-based method I developed. Thanks to jedediah referring me to this paper, I managed to rebuild the codes and implement the simultaneous impulse based method with Projected-Gauss-Seidel (PGS) iterative solver as described by Erin Catto (mentioned in the reference of the paper as [Catt05]). So here's how it currently is: The simulation handles 2-dimensional rotating convex polygons. Detection is using separating-axis test, with a SKIN, meaning closest points between two polygons is detected and determined if their distance is less than SKIN. To resolve collision, simultaneous impulse-based method is used. It is solved using iterative solver (PGS-solver) as in Erin Catto's paper. Error-correction is implemented using Baumgarte's stabilization (you can refer to either paper for this) using J V = beta/dt*overlap, J is the Jacobian for the constraints, V the matrix containing the velocities of the bodies, beta an error-correction parameter that is better be < 1, dt the time-step taken by the engine, and overlap, the overlap between the bodies (true overlap, so SKIN is ignored). However, it is still less stable than I expected :s I tried to stack hexagons (or squares, doesn't really matter), and even with only 4 to 5 of them, they hardly stand still! Also note that I am not looking for a sleeping scheme. But I would settle if you have any explicit scheme to handle resting contacts. That said, I would be more than happy if you have a way of treating it generally (as continuous collision, instead of explicitly as a special state). Ideas I have: I would try adding a damping term (proportional to velocity) to the Baumgarte. Is this a good idea in general? If not I would not want to waste my time trying to tune the parameter hoping it magically works. Ideas I have tried: Using simultaneous position based error correction as described in the paper in section 5.3.2, turned out to be worse than the current scheme. If you want to know the parameters I used: Hexagons, side 50 (pixels) gravity 2400 (pixels/sec^2) time-step 1/60 (sec) beta 0.1 restitution 0 to 0.2 coeff. of friction 0.2 PGS iteration 10 initial separation 10 (pixels) mass 1 (unit is irrelevant for now, i modified velocity directly<-impulse method) inertia 1/1000 Thanks in advance! I really appreciate any help from you guys!! :)

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  • Remove box2d bodies after collision deduction android?

    - by jubin
    Can any one explain me how to destroy box2d body when collide i have tried but my application crashed.First i have checked al collisions then add all the bodies in array who i want to destroy.I am trying to learning this tutorial My all the bodies are falling i want these bodies should destroy when these bodies will collide my actor monkey but when it collide it destroy but my aplication crashed.I have googled and from google i got the application crash reasons we should not destroy body in step funtion but i am removing body in the last of tick method. could any one help me or provide me code aur check my code why i am getting this prblem or how can i destroy box2d bodies. This is my code what i am doing. Please could any one check my code and tell me what is i am doing wrong for removing bodies. The code is for multiple box2d objects falling on my actor monkey it should be destroy when it will fall on the monkey.It is destroing but my application crahes. static class Box2DLayer extends CCLayer { protected static final float PTM_RATIO = 32.0f; protected static final float WALK_FACTOR = 3.0f; protected static final float MAX_WALK_IMPULSE = 0.2f; protected static final float ANIM_SPEED = 0.3f; int isLeft=0; String dir=""; int x =0; float direction; CCColorLayer objectHint; // protected static final float PTM_RATIO = 32.0f; protected World _world; protected static Body spriteBody; CGSize winSize = CCDirector.sharedDirector().winSize(); private static int count = 200; protected static Body monkey_body; private static Body bodies; CCSprite monkey; float animDelay; int animPhase; CCSpriteSheet danceSheet = CCSpriteSheet.spriteSheet("phases.png"); CCSprite _block; List<Body> toDestroy = new ArrayList<Body>(); //CCSpriteSheet _spriteSheet; private static MyContactListener _contactListener = new MyContactListener(); public Box2DLayer() { this.setIsAccelerometerEnabled(true); CCSprite bg = CCSprite.sprite("jungle.png"); addChild(bg,0); bg.setAnchorPoint(0,0); bg.setPosition(0,0); CGSize s = CCDirector.sharedDirector().winSize(); // Use scaled width and height so that our boundaries always match the current screen float scaledWidth = s.width/PTM_RATIO; float scaledHeight = s.height/PTM_RATIO; Vector2 gravity = new Vector2(0.0f, -30.0f); boolean doSleep = false; _world = new World(gravity, doSleep); // Create edges around the entire screen // Define the ground body. BodyDef bxGroundBodyDef = new BodyDef(); bxGroundBodyDef.position.set(0.0f, 0.0f); // The body is also added to the world. Body groundBody = _world.createBody(bxGroundBodyDef); // Register our contact listener // Define the ground box shape. PolygonShape groundBox = new PolygonShape(); Vector2 bottomLeft = new Vector2(0f,0f); Vector2 topLeft = new Vector2(0f,scaledHeight); Vector2 topRight = new Vector2(scaledWidth,scaledHeight); Vector2 bottomRight = new Vector2(scaledWidth,0f); // bottom groundBox.setAsEdge(bottomLeft, bottomRight); groundBody.createFixture(groundBox,0); // top groundBox.setAsEdge(topLeft, topRight); groundBody.createFixture(groundBox,0); // left groundBox.setAsEdge(topLeft, bottomLeft); groundBody.createFixture(groundBox,0); // right groundBox.setAsEdge(topRight, bottomRight); groundBody.createFixture(groundBox,0); CCSprite floorbg = CCSprite.sprite("grassbehind.png"); addChild(floorbg,1); floorbg.setAnchorPoint(0,0); floorbg.setPosition(0,0); CCSprite floorfront = CCSprite.sprite("grassfront.png"); floorfront.setTag(2); this.addBoxBodyForSprite(floorfront); addChild(floorfront,3); floorfront.setAnchorPoint(0,0); floorfront.setPosition(0,0); addChild(danceSheet); //CCSprite monkey = CCSprite.sprite(danceSheet, CGRect.make(0, 0, 48, 73)); //addChild(danceSprite); monkey = CCSprite.sprite("arms_up.png"); monkey.setTag(2); monkey.setPosition(200,100); BodyDef spriteBodyDef = new BodyDef(); spriteBodyDef.type = BodyType.DynamicBody; spriteBodyDef.bullet=true; spriteBodyDef.position.set(200 / PTM_RATIO, 300 / PTM_RATIO); monkey_body = _world.createBody(spriteBodyDef); monkey_body.setUserData(monkey); PolygonShape spriteShape = new PolygonShape(); spriteShape.setAsBox(monkey.getContentSize().width/PTM_RATIO/2, monkey.getContentSize().height/PTM_RATIO/2); FixtureDef spriteShapeDef = new FixtureDef(); spriteShapeDef.shape = spriteShape; spriteShapeDef.density = 2.0f; spriteShapeDef.friction = 0.70f; spriteShapeDef.restitution = 0.0f; monkey_body.createFixture(spriteShapeDef); //Vector2 force = new Vector2(10, 10); //monkey_body.applyLinearImpulse(force, spriteBodyDef.position); addChild(monkey,10000); this.schedule(tickCallback); this.schedule(createobjects, 2.0f); objectHint = CCColorLayer.node(ccColor4B.ccc4(255,0,0,128), 200f, 100f); addChild(objectHint, 15000); objectHint.setVisible(false); _world.setContactListener(_contactListener); } private UpdateCallback tickCallback = new UpdateCallback() { public void update(float d) { tick(d); } }; private UpdateCallback createobjects = new UpdateCallback() { public void update(float d) { secondUpdate(d); } }; private void secondUpdate(float dt) { this.addNewSprite(); } public void addBoxBodyForSprite(CCSprite sprite) { BodyDef spriteBodyDef = new BodyDef(); spriteBodyDef.type = BodyType.StaticBody; //spriteBodyDef.bullet=true; spriteBodyDef.position.set(sprite.getPosition().x / PTM_RATIO, sprite.getPosition().y / PTM_RATIO); spriteBody = _world.createBody(spriteBodyDef); spriteBody.setUserData(sprite); Vector2 verts[] = { new Vector2(-11.8f / PTM_RATIO, -24.5f / PTM_RATIO), new Vector2(11.7f / PTM_RATIO, -24.0f / PTM_RATIO), new Vector2(29.2f / PTM_RATIO, -14.0f / PTM_RATIO), new Vector2(28.7f / PTM_RATIO, -0.7f / PTM_RATIO), new Vector2(8.0f / PTM_RATIO, 18.2f / PTM_RATIO), new Vector2(-29.0f / PTM_RATIO, 18.7f / PTM_RATIO), new Vector2(-26.3f / PTM_RATIO, -12.2f / PTM_RATIO) }; PolygonShape spriteShape = new PolygonShape(); spriteShape.set(verts); //spriteShape.setAsBox(sprite.getContentSize().width/PTM_RATIO/2, //sprite.getContentSize().height/PTM_RATIO/2); FixtureDef spriteShapeDef = new FixtureDef(); spriteShapeDef.shape = spriteShape; spriteShapeDef.density = 2.0f; spriteShapeDef.friction = 0.70f; spriteShapeDef.restitution = 0.0f; spriteShapeDef.isSensor=true; spriteBody.createFixture(spriteShapeDef); } public void addNewSprite() { count=0; Random rand = new Random(); int Number = rand.nextInt(10); switch(Number) { case 0: _block = CCSprite.sprite("banana.png"); break; case 1: _block = CCSprite.sprite("backpack.png");break; case 2: _block = CCSprite.sprite("statue.png");break; case 3: _block = CCSprite.sprite("pineapple.png");break; case 4: _block = CCSprite.sprite("bananabunch.png");break; case 5: _block = CCSprite.sprite("hat.png");break; case 6: _block = CCSprite.sprite("canteen.png");break; case 7: _block = CCSprite.sprite("banana.png");break; case 8: _block = CCSprite.sprite("statue.png");break; case 9: _block = CCSprite.sprite("hat.png");break; } int padding=20; //_block.setPosition(CGPoint.make(100, 100)); // Determine where to spawn the target along the Y axis CGSize winSize = CCDirector.sharedDirector().displaySize(); int minY = (int)(_block.getContentSize().width / 2.0f); int maxY = (int)(winSize.width - _block.getContentSize().width / 2.0f); int rangeY = maxY - minY; int actualY = rand.nextInt(rangeY) + minY; // Create block and add it to the layer float xOffset = padding+_block.getContentSize().width/2+((_block.getContentSize().width+padding)*count); _block.setPosition(CGPoint.make(actualY, 750)); _block.setTag(1); float w = _block.getContentSize().width; objectHint.setVisible(true); objectHint.changeWidth(w); objectHint.setPosition(actualY-w/2, 460); this.addChild(_block,10000); // Create ball body and shape BodyDef ballBodyDef1 = new BodyDef(); ballBodyDef1.type = BodyType.DynamicBody; ballBodyDef1.position.set(actualY/PTM_RATIO, 480/PTM_RATIO); bodies = _world.createBody(ballBodyDef1); bodies.setUserData(_block); PolygonShape circle1 = new PolygonShape(); Vector2 verts[] = { new Vector2(-11.8f / PTM_RATIO, -24.5f / PTM_RATIO), new Vector2(11.7f / PTM_RATIO, -24.0f / PTM_RATIO), new Vector2(29.2f / PTM_RATIO, -14.0f / PTM_RATIO), new Vector2(28.7f / PTM_RATIO, -0.7f / PTM_RATIO), new Vector2(8.0f / PTM_RATIO, 18.2f / PTM_RATIO), new Vector2(-29.0f / PTM_RATIO, 18.7f / PTM_RATIO), new Vector2(-26.3f / PTM_RATIO, -12.2f / PTM_RATIO) }; circle1.set(verts); FixtureDef ballShapeDef1 = new FixtureDef(); ballShapeDef1.shape = circle1; ballShapeDef1.density = 10.0f; ballShapeDef1.friction = 0.0f; ballShapeDef1.restitution = 0.1f; bodies.createFixture(ballShapeDef1); count++; //Remove(); } @Override public void ccAccelerometerChanged(float accelX, float accelY, float accelZ) { //Apply the directional impulse /*float impulse = monkey_body.getMass()*accelY*WALK_FACTOR; Vector2 force = new Vector2(impulse, 0); monkey_body.applyLinearImpulse(force, monkey_body.getWorldCenter());*/ walk(accelY); //Remove(); } private void walk(float accelY) { // TODO Auto-generated method stub direction = accelY; } private void Remove() { for (Iterator<MyContact> it1 = _contactListener.mContacts.iterator(); it1.hasNext();) { MyContact contact = it1.next(); Body bodyA = contact.fixtureA.getBody(); Body bodyB = contact.fixtureB.getBody(); // See if there's any user data attached to the Box2D body // There should be, since we set it in addBoxBodyForSprite if (bodyA.getUserData() != null && bodyB.getUserData() != null) { CCSprite spriteA = (CCSprite) bodyA.getUserData(); CCSprite spriteB = (CCSprite) bodyB.getUserData(); // Is sprite A a cat and sprite B a car? If so, push the cat // on a list to be destroyed... if (spriteA.getTag() == 1 && spriteB.getTag() == 2) { //Log.v("dsfds", "dsfsd"+bodyA); //_world.destroyBody(bodyA); // removeChild(spriteA, true); toDestroy.add(bodyA); } // Is sprite A a car and sprite B a cat? If so, push the cat // on a list to be destroyed... else if (spriteA.getTag() == 2 && spriteB.getTag() == 1) { //Log.v("dsfds", "dsfsd"+bodyB); toDestroy.add(bodyB); } } } // Loop through all of the box2d bodies we want to destroy... for (Iterator<Body> it1 = toDestroy.iterator(); it1.hasNext();) { Body body = it1.next(); // See if there's any user data attached to the Box2D body // There should be, since we set it in addBoxBodyForSprite if (body.getUserData() != null) { // We know that the user data is a sprite since we set // it that way, so cast it... CCSprite sprite = (CCSprite) body.getUserData(); // Remove the sprite from the scene _world.destroyBody(body); removeChild(sprite, true); } // Destroy the Box2D body as well // _contactListener.mContacts.remove(0); } } public synchronized void tick(float delta) { synchronized (_world) { _world.step(delta, 8, 3); //_world.clearForces(); //addNewSprite(); } CCAnimation danceAnimation = CCAnimation.animation("dance", 1.0f); // Iterate over the bodies in the physics world Iterator<Body> it = _world.getBodies(); while(it.hasNext()) { Body b = it.next(); Object userData = b.getUserData(); if (userData != null && userData instanceof CCSprite) { //Synchronize the Sprites position and rotation with the corresponding body CCSprite sprite = (CCSprite)userData; if(sprite.getTag()==1) { //b.applyLinearImpulse(force, pos); sprite.setPosition(b.getPosition().x * PTM_RATIO, b.getPosition().y * PTM_RATIO); sprite.setRotation(-1.0f * ccMacros.CC_RADIANS_TO_DEGREES(b.getAngle())); } else { //Apply the directional impulse float impulse = monkey_body.getMass()*direction*WALK_FACTOR; Vector2 force = new Vector2(impulse, 0); b.applyLinearImpulse(force, b.getWorldCenter()); sprite.setPosition(b.getPosition().x * PTM_RATIO, b.getPosition().y * PTM_RATIO); animDelay -= 1.0f/60.0f; if(animDelay <= 0) { animDelay = ANIM_SPEED; animPhase++; if(animPhase > 2) { animPhase = 1; } } if(direction < 0 ) { isLeft=1; } else { isLeft=0; } if(isLeft==1) { dir = "left"; } else { dir = "right"; } float standingLimit = (float) 0.1f; float vX = monkey_body.getLinearVelocity().x; if((vX > -standingLimit)&& (vX < standingLimit)) { // Log.v("sasd", "standing"); } else { } } } } Remove(); } } Sorry for my english. Thanks in advance.

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  • WCF hosting: Can access svc file but cannot go to wsdl link

    - by Impulse
    Hello, I have a WCF service that is hosted in IIS 7.5. I have two servers, one for test and one for production. The service works fine on test server, but on the production server I have the following error. When I access the address http//..../service.svc I can see the default page that says: You have created a service. To test this service, you will need to create a client and use it to call the service. You can do this using the svcutil.exe tool from the command line with the following syntax: svcutil.exe http://..../service.svc?wsdl This will generate a configuration file and a code file that contains the client class. Add the two files to your client application and use the generated client class to call the Service. But when I click the wsdl link, I cannot go to the wsdl page. It returns me to this default web page without any errors. I am suspecting a network/firewall authorization error but does anybody have an experience like this one? All IIS settings are the same for test and production servers. Thank you, Best Regards.

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  • Movement of body after applying weld joint

    - by ved
    I have two rectangular bodies. I've applied Weldjoint successfully on these bodies. I want to move that joined body by applying linear impulse. After weld joint, these two bodies becomes single body right? How do I apply force/impulse on the joined body? I am using Box2D with LibGDX. I've tried this: polygon1.applyLinearImpulse(new Vector2(-5, 0), polygon1.getWorldCenter(), true); I thought that if I move polygon1 then polygon2 will also move due to my weld joint but it is not working properly. Why don't they move together after being welded?

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  • Behavior tree implementation details

    - by angryInsomniac
    I have been looking around for implementation details of behavior trees, the best descriptions I found were by Alex Champarand and some of Damian Isla's talk about AI in Halo 2 (the video of which is locked up in the GDC vault sadly). However, both descriptions fall short of helping one actually create a BT, one particular question has been bugging me for a while. When is the tree in a behavior tree evaluated? Furthermore: If the tree is in the middle of executing a sequence of actions (patrolling waypoints) and a higher priority impulse comes in (distraction sound) , how to switch to that side of the tree seamlessly without resorting to a state machine like system and if it is decided that the impulse was irrelevant (the distraction is too far away to affect this guard), how to go back to the last thing that the guard was doing ? I have quite a few questions like this and I don't wish to flood the board with separate queries so if you know of any resource where questions like these can be answered I would be very grateful.

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  • What does the symbol ::: mean in R

    - by Milktrader
    I came across this in the following context from B. Pfaff's "Analysis of Integrated and Cointegrated Time Series in R" ## Impulse response analysis of SVAR A-type model 1 args (vars ::: irf.svarest) 2 irf.svara <- irf (svar.A, impulse = ”y1 ” , 3 response = ”y2 ” , boot = FALSE) 4 args (vars ::: plot.varirf) 5 plot (irf.svara)

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  • I need help with 2D collision response (of stacking rotating polygons, with friction and gravity, for a game)

    - by Register Sole
    Hi I am looking for suggestions on how to write a collision response for game programming purpose (so not a scientific simulation). I am dealing with 2D polygons that are rotating, and I want them to be able to stack. I also want friction and gravity. I have a detection mechanism that returns the separating axis, how long the polygons are overlapping, and up to 2 points of contact. For the response, I am currently using an impulse-based response, which main idea is: find the separating axis, length of overlap, and the point of contact (if there are two, pick a random point between to simulate averaged force. i believe there are better ways than this) separate the object (modifying their positions, taking into account of their masses. i do not separate them completely though, to keep track that they are colliding to reduce jitter) calculate normal force based on the coefficient of restitution as if there is no friction. calculate friction, as if there is no normal force. I also assume that the direction of the friction is the same throughout the collision. apply the two forces (which result in a rather inaccurate result, since each force is calculated as if the other is not present. for non-rotating bodies though, this method is exact) I am aware that this method requires the coefficient of friction to be sufficiently small due to the assumption that the direction of friction stays the same in a collision. Also, the result is visually satisfying if gravity is not present. However, when there is gravity, objects on ground jitter and drift (even with zero coefficient of restitution)! It also happens for stacking objects. Larger coefficient of restitution and gravity increase the jittering. I hope you can help me with this. Some things i would like to know more about is how to handle collision with two point of contacts (how to end up having an object sitting still on the ground?), how to reduce, and prevent if possible, jitter and drift (do people use the most accurate method possible, or is there a trick to overcome this?), and how to handle multiple objects collision (for example, in the case of stacking objects, how do I check collisions between all of them and keep them all stable at every frame so they don't jitter?). A total reformulation of my algorithm is also welcomed, as long as it works. Another thing to note is that I am not making a Physics game, so I only need a visually satisfying response (though a realistic response is preferable, if it is not performance-heavy). But surely jittering and drifting objects on flat ground are not at all acceptable. In addition, I am a Physics student, so feel free to talk about impulse and whatever needed. Finally, I'm sorry for the long post. I tried to be as concise as I can. Thank you for reading it! EDIT It seems what I didn't manage to come up all this time is to separate resting contact as a class of its own and how to solve them. Currently reading the paper suggested by Jedediah. More suggestions on the topic are welcome :) CASE CLOSED After reading various papers referenced in the paper, successfully implemented simultaneous impulse method (referring to the original paper by Erin Catto, [Catt05]). Thanks maaaan!! The paper is wonderful. The current system is visibly much better than the previous. Still haven't separated resting contact as a class of its own though, which brings me to my next question. Love you all! Haha (sorry, I'm just so happy thanks to you).

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  • CodePlex Daily Summary for Friday, November 23, 2012

    CodePlex Daily Summary for Friday, November 23, 2012Popular ReleasesLiberty: v3.4.3.0 Release 23rd November 2012: Change Log -Added -H4 A dialog which gives further instructions when attempting to open a "Halo 4 Data" file -H4 Added a short note to the weapon editor stating that dropping your weapons will cap their ammo -Reach Edit the world's gravity -Reach Fine invincibility controls in the object editor -Reach Edit object velocity -Reach Change the teams of AI bipeds and vehicles -Reach Enable/disable fall damage on the biped editor screen -Reach Make AIs deaf and/or blind in the objec...Umbraco CMS: Umbraco 4.11.0: NugetNuGet BlogRead the release blog post for 4.11.0. Whats new50 bugfixes (see the issue tracker for a complete list) Read the documentation for the MVC bits. Breaking changesNone since 4.10.0 NoteIf you need Courier use the release candidate (as of build 26). The code editor has been greatly improved, but is sometimes problematic in Internet Explorer 9 and lower. Previously it was just disabled for IE and we recommend you disable it in umbracoSettings.config (scriptDisableEditor) if y...VidCoder: 1.4.8 Beta: Fixed encode failures when including chapter markers (Regression in 1.4.7).Audio Pitch & Shift: Audio Pitch And Shift 5.1.0.3: Fixed supported files list on open dialog (added .pls and .m3u) Impulse Media Player splash message (can be disabled anyway)LiveChat Starter Kit: LCSK 2.0 alpha: This is an early preview of the LiveChat Starter Kit version 2 using SignalR as the core communication mechanism. To add LCSK to an existing ASP.NET app do the following: Copy the LCSK folder to your ASP.NET project Install SignalR form your package manager window Install-Package SignalR Include the following javascript tags where you want the visitor to see the chat box: <script src="/Scripts/jquery.signalR-0.5.3.min.js" type="text/javascript"></script> <script src="/signalr/hubs" typ...Impulse Media Player: Impulse Media Player 1.0.0.0: Impulse Media Player is born !!!patterns & practices - HiloJS: a Windows Store app using JavaScript: Source with Unit Tests: This source is also available under the _Source Code tab. See the folder Hilo.Specifications.Rackspace Cloud Files Manager: Rackspace Cloud Files Manager v1: Rackspace Cloud Files Manager v1MJPEG Decoder: MJPEG Decoder v1.2: Added support for WinRT (ARM and x86/x64) Added support for Windows Phone 8 Added Error event to catch connection exceptions (thanks to Mirek Czerwinski for the idea) Note that the XNA and WP7 assemblies remain at v1.1 and do not contain this addition Samples for WinRT in C#/XAML and HTML/JavaScript (in source code repository) Sample for Windows Phone 8 in C#/XAML (in source code repository)ServiceMon - Extensible Real-time, Service Monitoring Utility for Windows: ServiceMon Release 1.2.0.58: Auto-uploaded from build serverImapX 2: ImapX 2.0.0.6: An updated release of the ImapX 2 library, containing many bugfixes for both, the library and the sample application.WiX Toolset: WiX v3.7 RC: WiX v3.7 RC (3.7.1119.0) provides feature complete Bundle update and reference tracking plus several bug fixes. For more information see Rob's blog post about the release: http://robmensching.com/blog/posts/2012/11/20/WiX-v3.7-Release-Candidate-availablePicturethrill: Version 2.11.20.0: Fixed up Bing image provider on Windows 8Excel AddIn to reset the last worksheet cell: XSFormatCleaner.xla: Modified the commandbar code to use CommandBar IDs instead of English names.Json.NET: Json.NET 4.5 Release 11: New feature - Added ITraceWriter, MemoryTraceWriter, DiagnosticsTraceWriter New feature - Added StringEscapeHandling with options to escape HTML and non-ASCII characters New feature - Added non-generic JToken.ToObject methods New feature - Deserialize ISet<T> properties as HashSet<T> New feature - Added implicit conversions for Uri, TimeSpan, Guid New feature - Missing byte, char, Guid, TimeSpan and Uri explicit conversion operators added to JToken New feature - Special case...EntitiesToDTOs - Entity Framework DTO Generator: EntitiesToDTOs.v3.0: DTOs and Assemblers can be generated inside project folders! Choose the types you want to generate! Support for Visual Studio 2012 !!! Support for new Entity Framework EDMX (format used by VS2012) ! Support for Enum Types! Optional automatic check for updates! Added the following methods to Assemblers! IEnumerable<DTO>.ToEntities() : ICollection<Entity> IEnumerable<Entity>.ToDTOs() : ICollection<DTO> Indicate class identifier for DTOs and Assemblers! Cleaner Assemblers code....mojoPortal: 2.3.9.4: see release notes on mojoportal.com http://www.mojoportal.com/mojoportal-2394-released Note that we have separate deployment packages for .NET 3.5 and .NET 4.0, but we recommend you to use .NET 4, we will probably drop support for .NET 3.5 once .NET 4.5 is available The deployment package downloads on this page are pre-compiled and ready for production deployment, they contain no C# source code and are not intended for use in Visual Studio. To download the source code see getting the lates...DotNetNuke® Store: 03.01.07: What's New in this release? IMPORTANT: this version requires DotNetNuke 04.06.02 or higher! DO NOT REPORT BUGS HERE IN THE ISSUE TRACKER, INSTEAD USE THE DotNetNuke Store Forum! Bugs corrected: - Replaced some hard coded references to the default address provider classes by the corresponding interfaces to allow the creation of another address provider with a different name. New Features: - Added the 'pickup' delivery option at checkout. - Added the 'no delivery' option in the Store Admin ...ExtJS based ASP.NET 2.0 Controls: FineUI v3.2.0: +2012-11-18 v3.2.0 -?????????????????SelectedValueArray????????(◇?◆:)。 -???????????????????RecoverPropertiesFromJObject????(〓?〓、????、??、Vian_Pan)。 -????????????,?????????????,???SelectedValueArray???????(sam.chang)。 -??Alert.Show???????????(swtseaman)。 -???????????????,??Icon??IconUrl????(swtseaman)。 -?????????TimePicker(??)。 -?????????,??/res.axd?css=blue.css&v=1。 -????????,?????????????,???????。 -????MenuCheckBox(???????)。 -?RadioButton??AutoPostBack??。 -???????FCKEditor?????????...BugNET Issue Tracker: BugNET 1.2: Please read our release notes for BugNET 1.2: http://blog.bugnetproject.com/bugnet-1-2-has-been-released Please do not post questions as reviews. Questions should be posted in the Discussions tab, where they will usually get promptly responded to. If you post a question as a review, you will pollute the rating, and you won't get an answer.New Projects1123case1325: Face everything you enccounting bravely and optimistically1123case1327: blessbestgifts4us1: Gift registry v2CPE-in: A LinkedIn like for CPE Lyon engineering schoolcsanid_cs_db: mvc db operatedurrrguffy: Example project in C# This project has a wide scope and will cover the basics of the dot net framework as it applies to office environment (including sharepoint). At the end of this project, you will be able to call yourself a sharepoint developer. Epic Life: Achievements: An attempt to adapt the achievement system from games to the real life. Something between a to-do manager and a "done-in-this-year"-list. NOT A TO-DO MANAGERGeoVIP: ??????? ??? ?????????????? ?????????? ??????? ???????? ????? ?????????GTcfla KM: ??????????????????????????.??????Oracle????Java????Harlinn Windows: A C++ library targeting Windows 7 and aboveIdentityModel.Tools: Tools to support WIF with .NET 4.5jean1123-1326: rLOLSimulator: AMacroprocesos: Gestión de los procesos existentes en una empresa, así como del control de su ocumentaciónMakeQuestionaryProject: Projeto de geração de questionários dinâmicosMrCMS - ASP.NET MVC Open source CMS: MrCMS is an open source ASP.NET MVC content management system. MyWebApplication: WebApplication Next Code Generator: Next.CodeGen project is a simple application generator that offers a command line interface in order to help developers create WPF applications.Orchard backend additions: Proof of concept for combining translated contenitems and version in the backend content item listProgrammer's Color Picker for C# and WPF: Wybór koloru dla programisty C# i WPFProjet Flux RSS EPSI W: It's a project for windows 8 applicationSpander: Spander ist ein Open-Source VOS (Virtual Operating System).SQLServer Database Browser: It's a simple SQLServer Database Browser for simple query .TemplateCodeGenerator: ????????。???????。Vector Rumble WP7: navmesh navigation demo running on wp7VSDBM - Viral Sequence Data Base Manager: VSDBM - Viral Sequence Database ManagerWebApp2013: Please develop HTML5 mobile web apps rater than native mobile apps! This project is used in my training as MCT for microsoft certified WebApp Developer 70-480.Windows Phone Streaming Media: HTTP Live Streaming (HLS) for Windows Phone.WixDeploymentExtension: Extension support Biztalk Application deployment, Business Activity Monitor (BAM) Deployment and VSDBCMD based SQL deployment and SQLCMD script execution.

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  • How do I prevent other dynamic bodies from affecting the player's velocity with Box2D?

    - by Milo
    I'm working on my player object for my game. PhysicsBodyDef def; def.fixedRotation = true; def.density = 1.0f; def.position = Vec2(200.0f, 200.0f); def.isDynamic = true; def.size = Vec2(50.0f,200.0f); m_player.init(def,&m_physicsEngine.getWorld()); This is how he moves: b2Vec2 vel = getBody()->GetLinearVelocity(); float desiredVel = 0; if (m_keys[ALLEGRO_KEY_A] || m_keys[ALLEGRO_KEY_LEFT]) { desiredVel = -5; } else if (m_keys[ALLEGRO_KEY_D] || m_keys[ALLEGRO_KEY_RIGHT]) { desiredVel = 5; } else { desiredVel = 0; } float velChange = desiredVel - vel.x; float impulse = getBody()->GetMass() * velChange; //disregard time factor getBody()->ApplyLinearImpulse( b2Vec2(impulse,0), getBody()->GetWorldCenter(),true); This creates a few problems. First, to move the player at a constant speed he must be given a high velocity. The problem with this is if he just comes in contact with a small box, he makes it move a lot. Now, I can fix this by lowering his density, but then comes my main issue: I need other objects to be able to run into him, but when they do, he should be like a static wall and not move. I'm not sure how to do that without high density. I cannot use collision groups since I still need him to be solid toward other dynamic things. How can this be done? Essentially, how do I prevent other dynamic bodies from affecting the player's velocity?

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  • Good 2D Platformer Physics

    - by Joe Wreschnig
    I have a basic character controller set up for a 2D platformer with Box2D, and I'm starting to tweak it to try to make it feel good. Physics engines have a lot of knobs to tweak, and it's not clear to me, writing with a physics engine for the first time, which ones I should use. Should jumping apply a force for several ticks? An impulse? Directly set velocity? How do I stop the avatar from sticking to walls without taking away all its friction (or do I take away all the friction, but only in the air)? Should I model the character as a capsule? A box with rounded corners? A box with two wheels? Just one big wheel? I feel like someone must have done this before! There seem to be very few resources available on the web that are not "baby's first physics", which all cut off where I'm hoping someone has already solved the issues. Most examples of physics engines for platformers have floaty-feeling controls, or in-air jumps, or easily exploitable behavior when temporary penetration is too high, etc. Some examples of what I mean: A short tap of jump jumps a short distance; a long tap jumps higher. Short skidding when stopping or reversing directions at high velocity. Standing stably on inclines (but maybe sliding down them when ducking). Analog speed when using an analog controller. All the other things that separate good platformers from bad platformers. Dare I suggest, stable moving platforms? I'm not really looking for "hey, do this." Obviously, the right thing to do is dependent on what I want in the game. But I'm hoping someone somewhere has gone through the possibilities and said "well technique A does feature X well, technique B does Y well, but that doesn't work with C", or has some worked examples beyond "if (key == space) character.impulse(0, 1)"

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  • Ball to Ball Collision - Detection and Handling

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

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  • Pool Billiard AI

    - by Sebi
    Im implementing a pool billiard game in Java and it all works fine. It is a multiplayer game, but nevertheless, it should also be possible to play it alone. For this purpose I'm trying to implement a simple KI. At the moment, the KI choose just randomly a direction and a random intensity of the impulse (don't know the correct english word for that). Of course this AI is very poor and unlikely to ever challenge a player. So i thought about improving the KI, but there are several hard to solve problems. First I thought of just choosing the nearest ball and to try to put it directly into the nearest hole. This isn't that bad, but if there other balls in the line between, it isn't really working anymore. Additionally this dosn't solve te problem of calculating the intensity of the impulse. So are there any general advice? Or any ideas? Best practices?

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  • Single and Double Jump with single button.

    - by Asad
    I want to make Single Jump on Single Tap and Double Jump on Double Tap. My problem is that if I make double Tap on ground then it’s fine but if I make first Tap on ground and second Tap in Air then Player gain more height then usual As in image 1. I want to Make my jump like in Image 2, No matter from which point user gives second Tap, player Always get a specific height. I Used both Impulse and Linear velocity to make Jump but my problem did not solved.

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  • Any advice for dynamic music control?

    - by Assembler
    I would like to be able to dynamically progress the score, and affect the volume levels of separate channels within the music. How could I do this? From my experience with mod music (olden days Amiga music, Mod Tracker, Scream Tracker, Fast Tracker II, Impulse Tracker etc etc), I believe this is the best way to tackle the problem, to allow the music to move from one loop to another, without anything mixed down. I want to do this in AS3, and am considering pulling apart Flod to make this happen

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  • Using the Static Code Analysis feature of Visual Studio (Premium/Ultimate) to find memory leakage problems

    - by terje
    Memory for managed code is handled by the garbage collector, but if you use any kind of unmanaged code, like native resources of any kind, open files, streams and window handles, your application may leak memory if these are not properly handled.  To handle such resources the classes that own these in your application should implement the IDisposable interface, and preferably implement it according to the pattern described for that interface. When you suspect a memory leak, the immediate impulse would be to start up a memory profiler and start digging into that.   However, before you follow that impulse, do a Static Code Analysis run with a ruleset tuned to finding possible memory leaks in your code.  If you get any warnings from this, fix them before you go on with the profiling. How to use a ruleset In Visual Studio 2010 (Premium and Ultimate editions) you can define your own rulesets containing a list of Static Code Analysis checks.   I have defined the memory checks as shown in the lists below as ruleset files, which can be downloaded – see bottom of this post.  When you get them, you can easily attach them to every project in your solution using the Solution Properties dialog. Right click the solution, and choose Properties at the bottom, or use the Analyze menu and choose “Configure Code Analysis for Solution”: In this dialog you can now choose the Memorycheck ruleset for every project you want to investigate.  Pressing Apply or Ok opens every project file and changes the projects code analysis ruleset to the one we have specified here. How to define your own ruleset  (skip this if you just download my predefined rulesets) If you want to define the ruleset yourself, open the properties on any project, choose Code Analysis tab near the bottom, choose any ruleset in the drop box and press Open Clear out all the rules by selecting “Source Rule Sets” in the Group By box, and unselect the box Change the Group By box to ID, and select the checks you want to include from the lists below. Note that you can change the action for each check to either warning, error or none, none being the same as unchecking the check.   Now go to the properties window and set a new name and description for your ruleset. Then save (File/Save as) the ruleset using the new name as its name, and use it for your projects as detailed above. It can also be wise to add the ruleset to your solution as a solution item. That way it’s there if you want to enable Code Analysis in some of your TFS builds.   Running the code analysis In Visual Studio 2010 you can either do your code analysis project by project using the context menu in the solution explorer and choose “Run Code Analysis”, you can define a new solution configuration, call it for example Debug (Code Analysis), in for each project here enable the Enable Code Analysis on Build   In Visual Studio Dev-11 it is all much simpler, just go to the Solution root in the Solution explorer, right click and choose “Run code analysis on solution”.     The ruleset checks The following list is the essential and critical memory checks.  CheckID Message Can be ignored ? Link to description with fix suggestions CA1001 Types that own disposable fields should be disposable No  http://msdn.microsoft.com/en-us/library/ms182172.aspx CA1049 Types that own native resources should be disposable Only if the pointers assumed to point to unmanaged resources point to something else  http://msdn.microsoft.com/en-us/library/ms182173.aspx CA1063 Implement IDisposable correctly No  http://msdn.microsoft.com/en-us/library/ms244737.aspx CA2000 Dispose objects before losing scope No  http://msdn.microsoft.com/en-us/library/ms182289.aspx CA2115 1 Call GC.KeepAlive when using native resources See description  http://msdn.microsoft.com/en-us/library/ms182300.aspx CA2213 Disposable fields should be disposed If you are not responsible for release, of if Dispose occurs at deeper level  http://msdn.microsoft.com/en-us/library/ms182328.aspx CA2215 Dispose methods should call base class dispose Only if call to base happens at deeper calling level  http://msdn.microsoft.com/en-us/library/ms182330.aspx CA2216 Disposable types should declare a finalizer Only if type does not implement IDisposable for the purpose of releasing unmanaged resources  http://msdn.microsoft.com/en-us/library/ms182329.aspx CA2220 Finalizers should call base class finalizers No  http://msdn.microsoft.com/en-us/library/ms182341.aspx Notes: 1) Does not result in memory leak, but may cause the application to crash   The list below is a set of optional checks that may be enabled for your ruleset, because the issues these points too often happen as a result of attempting to fix up the warnings from the first set.   ID Message Type of fault Can be ignored ? Link to description with fix suggestions CA1060 Move P/invokes to NativeMethods class Security No http://msdn.microsoft.com/en-us/library/ms182161.aspx CA1816 Call GC.SuppressFinalize correctly Performance Sometimes, see description http://msdn.microsoft.com/en-us/library/ms182269.aspx CA1821 Remove empty finalizers Performance No http://msdn.microsoft.com/en-us/library/bb264476.aspx CA2004 Remove calls to GC.KeepAlive Performance and maintainability Only if not technically correct to convert to SafeHandle http://msdn.microsoft.com/en-us/library/ms182293.aspx CA2006 Use SafeHandle to encapsulate native resources Security No http://msdn.microsoft.com/en-us/library/ms182294.aspx CA2202 Do not dispose of objects multiple times Exception (System.ObjectDisposedException) No http://msdn.microsoft.com/en-us/library/ms182334.aspx CA2205 Use managed equivalents of Win32 API Maintainability and complexity Only if the replace doesn’t provide needed functionality http://msdn.microsoft.com/en-us/library/ms182365.aspx CA2221 Finalizers should be protected Incorrect implementation, only possible in MSIL coding No http://msdn.microsoft.com/en-us/library/ms182340.aspx   Downloadable ruleset definitions I have defined three rulesets, one called Inmeta.Memorycheck with the rules in the first list above, and Inmeta.Memorycheck.Optionals containing the rules in the second list, and the last one called Inmeta.Memorycheck.All containing the sum of the two first ones.  All three rulesets can be found in the  zip archive  “Inmeta.Memorycheck” downloadable from here.   Links to some other resources relevant to Static Code Analysis MSDN Magazine Article by Mickey Gousset on Static Code Analysis in VS2010 MSDN :  Analyzing Managed Code Quality by Using Code Analysis, root of the documentation for this Preventing generated code from being analyzed using attributes Online training course on Using Code Analysis with VS2010 Blogpost by Tatham Oddie on custom code analysis rules How to write custom rules, from Microsoft Code Analysis Team Blog Microsoft Code Analysis Team Blog

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  • How to make the Angry Birds "shot arch" dotted line? [duplicate]

    - by unexpected62
    This question already has an answer here: Show path of a body of where it should go after linear impulse is applied 2 answers I am making a game that includes 2D projectile flight paths like that of Angry Birds. Angry Birds employs the notion that a previous shot is shown with a dotted line "arch" showing the player where that last shot went. I think recording that data is simple enough once a shot is fired, but in my game, I want to show it preemptively, ie: before the shot. How would I go about calculating this dotted line? The other caveat is I have wind in my game. How can you determine a projectile preemptively when wind will affect it too? This seems like a pretty tough problem. My wind right now just applies a constant force every step of animation in the direction of the wind flow. I'm using Box2D and AndEngine if it matters.

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  • AABB - AABB Collision, which face do I hit?

    - by PeeS
    To allow my objects to slide when they collide, I need to : Know which face of the AABB they collide with. Calculate the normal to that face. Return the normal and calculate the impulse that to apply to the player's velocity. Question How can I calculate which face of the AABB I collided with, knowing that I have two AABB's colliding? One is the player and the other is a world object. Here's what that looks like (problem collision circled in white): Thank you for your help.

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  • Box2Dweb very slow on node.js

    - by Peteris
    I'm using Box2Dweb on node.js. I have a rotated box object that I apply an impulse to move around. The timestep is set at 50ms, however, it bumps up to 100ms and even 200ms as soon as I add any more edges or boxes. Here are the edges I would like to use as bounds around the playing area: // Computing the corners var upLeft = new b2Vec2(0, 0), lowLeft = new b2Vec2(0, height), lowRight = new b2Vec2(width, height), upRight = new b2Vec2(width, 0) // Edges bounding the visible game area var edgeFixDef = new b2FixtureDef edgeFixDef.friction = 0.5 edgeFixDef.restitution = 0.2 edgeFixDef.shape = new b2PolygonShape var edgeBodyDef = new b2BodyDef; edgeBodyDef.type = b2Body.b2_staticBody edgeFixDef.shape.SetAsEdge(upLeft, lowLeft) world.CreateBody(edgeBodyDef).CreateFixture(edgeFixDef) edgeFixDef.shape.SetAsEdge(lowLeft, lowRight) world.CreateBody(edgeBodyDef).CreateFixture(edgeFixDef) edgeFixDef.shape.SetAsEdge(lowRight, upRight) world.CreateBody(edgeBodyDef).CreateFixture(edgeFixDef) edgeFixDef.shape.SetAsEdge(upRight, upLeft) world.CreateBody(edgeBodyDef).CreateFixture(edgeFixDef) Can box2d really become this slow for even two bodies or is there some pitfall? It would be very surprising given all the demos which successfully use tens of objects.

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  • Repelling a rigidbody in the direction an object is rotating

    - by ndg
    Working in Unity, I have a game object which I rotate each frame, like so: void Update() { transform.Rotate(new Vector3(0, 1, 0) * speed * Time.deltaTime); } However, I'm running into problems when it comes to applying a force to rigidbodies that collide with this game objects sphere collider. The effect I'm hoping to achieve is that objects which touch the collider are thrown in roughly the same direction as the object is rotating. To do this, I've tried the following: Vector3 force = ((transform.localRotation * Vector3.forward) * 2000) * Time.deltaTime; collision.gameObject.rigidbody.AddForce(force, ForceMode.Impulse); Unfortunately this doesn't always match the rotation of the object. To debug the issue, I wrote a simple OnDrawGizmos script, which (strangely) appears to draw the line correctly oriented to the rotation. void OnDrawGizmos() { Vector3 pos = transform.position + ((transform.localRotation * Vector3.forward) * 2); Debug.DrawLine(transform.position, pos, Color.red); } You can see the result of the OnDrawGizmos function below: What am I doing wrong?

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  • Specifying force and angle in ApplyImpulse in box2d

    - by Deepak Mahalingam
    I need to apply an impulse on a object with a particular force and at a particular angle in Box2d. If I am right the syntax would be the following: body.GetBody().ApplyImpulse(new b2Vec2(direction, power),body.GetBody().GetWorldCenter()); The problem is my direction is in angles. I found a discussion where it was said that the way we can convert an angle into a vector would be as: new b2Vec2(Math.cos(angle*Math.PI/180),Math.sin(angle*Math.PI/180)); Now I am not sure how to combine these two. In other words, if I wish to apply a force of 30 units at an angle of 30 degrees at the center of the object, how should I do it?

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