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  • x axis detection issues platformer starter kit

    - by dbomb101
    I've come across a problem with the collision detection code in the platformer starter kit for xna.It will send up the impassible flag on the x axis despite being nowhere near a wall in either direction on the x axis, could someone could tell me why this happens ? Here is the collision method. /// <summary> /// Detects and resolves all collisions between the player and his neighboring /// tiles. When a collision is detected, the player is pushed away along one /// axis to prevent overlapping. There is some special logic for the Y axis to /// handle platforms which behave differently depending on direction of movement. /// </summary> private void HandleCollisions() { // Get the player's bounding rectangle and find neighboring tiles. Rectangle bounds = BoundingRectangle; int leftTile = (int)Math.Floor((float)bounds.Left / Tile.Width); int rightTile = (int)Math.Ceiling(((float)bounds.Right / Tile.Width)) - 1; int topTile = (int)Math.Floor((float)bounds.Top / Tile.Height); int bottomTile = (int)Math.Ceiling(((float)bounds.Bottom / Tile.Height)) - 1; // Reset flag to search for ground collision. isOnGround = false; // For each potentially colliding tile, for (int y = topTile; y <= bottomTile; ++y) { for (int x = leftTile; x <= rightTile; ++x) { // If this tile is collidable, TileCollision collision = Level.GetCollision(x, y); if (collision != TileCollision.Passable) { // Determine collision depth (with direction) and magnitude. Rectangle tileBounds = Level.GetBounds(x, y); Vector2 depth = RectangleExtensions.GetIntersectionDepth(bounds, tileBounds); if (depth != Vector2.Zero) { float absDepthX = Math.Abs(depth.X); float absDepthY = Math.Abs(depth.Y); // Resolve the collision along the shallow axis. if (absDepthY < absDepthX || collision == TileCollision.Platform) { // If we crossed the top of a tile, we are on the ground. if (previousBottom <= tileBounds.Top) isOnGround = true; // Ignore platforms, unless we are on the ground. if (collision == TileCollision.Impassable || IsOnGround) { // Resolve the collision along the Y axis. Position = new Vector2(Position.X, Position.Y + depth.Y); // Perform further collisions with the new bounds. bounds = BoundingRectangle; } } //This is the section which deals with collision on the x-axis else if (collision == TileCollision.Impassable) // Ignore platforms. { // Resolve the collision along the X axis. Position = new Vector2(Position.X + depth.X, Position.Y); // Perform further collisions with the new bounds. bounds = BoundingRectangle; } } } } } // Save the new bounds bottom. previousBottom = bounds.Bottom; }

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  • How to detect which edges of a rectange touch when they collide in iOS

    - by Mike King
    I'm creating a basic "game" in iOS 4.1. The premise is simple, there is a green rectangle ("disk") that moves/bounces around the screen, and red rectangle ("bump") that is stationary. The user can move the red "bump" by touching another coordinate on the screen, but that's irrelevant to this question. Each rectangle is a UIImageView (I will replace them with some kind of image/icon once I get the mechanics down). I've gotten as far as detecting when the rectangles collide, and I'm able to reverse the direction of the green "disk" on the Y axis if they do. This works well when the green "disk" approaches the red "bump" from top or bottom, it bounces off in the other direction. But when it approaches from the side, the bounce is incorrect; I need to reverse the X direction instead. Here's the timer I setup: - (void)viewDidLoad { xSpeed = 3; ySpeed = -3; gameTimer = [NSTimer scheduledTimerWithTimeInterval:0.05 target:self selector:@selector(mainGameLoop:) userInfo:nil repeats:YES]; [super viewDidLoad]; } Here's the main game loop: - (void) mainGameLoop:(NSTimer *)theTimer { disk.center = CGPointMake(disk.center.x + xSpeed, disk.center.y + ySpeed); // make sure the disk does not travel off the edges of the screen // magic number values based on size of disk's frame // startAnimating causes the image to "pulse" if (disk.center.x < 55 || disk.center.x > 265) { xSpeed = xSpeed * -1; [disk startAnimating]; } if (disk.center.y < 55 || disk.center.y > 360) { ySpeed = ySpeed * -1; [disk startAnimating]; } // check to see if the disk collides with the bump if (CGRectIntersectsRect(disk.frame, bump.frame)) { NSLog(@"Collision detected..."); if (! [disk isAnimating]) { ySpeed = ySpeed * -1; [disk startAnimating]; } } } So my question is: how can I detect whether I need to flip the X speed or the Y speed? ie: how can I calculate which edge of the bump was collided with?

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  • Question about BoundingSpheres and Ray intersections

    - by NDraskovic
    I'm working on a XNA project (not really a game) and I'm having some trouble with picking algorithm. I have a few types of 3D models that I draw to the screen, and one of them is a switch. So I'm trying to make a picking algorithm that would enable the user to click on the switch and that would trigger some other function. The problem is that the BoundingSphere.Intersect() method always returns null as result. This is the code I'm using: In the declaration section: ` //Basic matrices private Matrix world = Matrix.CreateTranslation(new Vector3(0, 0, 0)); private Matrix view = Matrix.CreateLookAt(new Vector3(10, 10, 10), new Vector3(0, 0, 0), Vector3.UnitY); private Matrix projection = Matrix.CreatePerspectiveFieldOfView(MathHelper.ToRadians(45), 800f / 600f, 0.01f, 100f); //Collision detection variables Viewport mainViewport; List<BoundingSphere> spheres = new List<BoundingSphere>(); Ray ControlRay; Vector3 nearPoint, farPoint, nearPlane, farPlane, direction; ` And then in the Update method: ` nearPlane = new Vector3((float)Mouse.GetState().X, (float)Mouse.GetState().Y, 0.0f); farPlane = new Vector3((float)Mouse.GetState().X, (float)Mouse.GetState().Y, 10.0f); nearPoint = GraphicsDevice.Viewport.Unproject(nearPlane, projection, view, world); farPoint = GraphicsDevice.Viewport.Unproject(farPlane, projection, view, world); direction = farPoint - nearPoint; direction.Normalize(); ControlRay = new Ray(nearPoint, direction); if (spheres.Count != 0) { for (int i = 0; i < spheres.Count; i++) { if (spheres[i].Intersects(ControlRay) != null) { Window.Title = spheres[i].Center.ToString(); } else { Window.Title = "Empty"; } } ` The "spheres" list gets filled when the 3D object data gets loaded (I read it from a .txt file). For every object marked as switch (I use simple numbers to determine which object is to be drawn), a BoundingSphere is created (center is on the coordinates of the 3D object, and the diameter is always the same), and added to the list. The objects are drawn normally (and spheres.Count is not 0), I can see them on the screen, but the Window title always says "Empty" (of course this is just for testing purposes, I will add the real function when I get positive results) meaning that there is no intersection between the ControlRay and any of the bounding spheres. I think that my basic matrices (world, view and projection) are making some problems, but I cant figure out what. Please help.

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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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  • Custom collision

    - by bali182
    I was recently assigned to create a siple game using the Corona SDK. The main pillar of the game would be a simple event: the user should put a ball in a basket, and I should be able to handle this event. Here is a picture for better understanding: I successfully managed to create the collision shape for the basket, but i have trouble with the collision of the inside of this basket. My first thought was the following: create a new shape size and position it to fit the "belly" of this basket add it to the physics-world, and listen to the collision. With hybrid drawing it looks like this: But there is a problem: if i add this shape to the physics, it wouldn't let the ball fall into the, basket, it will handle this shape as a solid object as well. So my question is: How could I get this custom object to collide, without blocking the ball to fall through it? I have read a lots of forum post with similar questions but none of them got a proper answer. There must be a way to do this in an elegant way. And one note: Please don't suggest checking the collision manually, with rectangle intersection, because in this simple case it would work, but later I may need to change the shape of the basket, and then it will be useless!

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  • Point of contact of 2 OBBs?

    - 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 point of contact when I hit a wall. Here is my OBB class: public class OBB2D { private Vector2D projVec = new Vector2D(); private static Vector2D projAVec = new Vector2D(); private static Vector2D projBVec = new Vector2D(); private static Vector2D tempNormal = new Vector2D(); private Vector2D deltaVec = new Vector2D(); // Corners of the box, where 0 is the lower left. private Vector2D corner[] = new Vector2D[4]; private Vector2D center = new Vector2D(); private Vector2D extents = new Vector2D(); private RectF boundingRect = new RectF(); private float angle; //Two edges of the box extended away from corner[0]. private Vector2D axis[] = new Vector2D[2]; private double origin[] = new double[2]; public OBB2D(float centerx, float centery, float w, float h, float angle) { for(int i = 0; i < corner.length; ++i) { corner[i] = new Vector2D(); } for(int i = 0; i < axis.length; ++i) { axis[i] = new Vector2D(); } set(centerx,centery,w,h,angle); } public OBB2D(float left, float top, float width, float height) { for(int i = 0; i < corner.length; ++i) { corner[i] = new Vector2D(); } for(int i = 0; i < axis.length; ++i) { axis[i] = new Vector2D(); } set(left + (width / 2), top + (height / 2),width,height,0.0f); } public void set(float centerx,float centery,float w, float h,float angle) { float vxx = (float)Math.cos(angle); float vxy = (float)Math.sin(angle); float vyx = (float)-Math.sin(angle); float vyy = (float)Math.cos(angle); vxx *= w / 2; vxy *= (w / 2); vyx *= (h / 2); vyy *= (h / 2); corner[0].x = centerx - vxx - vyx; corner[0].y = centery - vxy - vyy; corner[1].x = centerx + vxx - vyx; corner[1].y = centery + vxy - vyy; corner[2].x = centerx + vxx + vyx; corner[2].y = centery + vxy + vyy; corner[3].x = centerx - vxx + vyx; corner[3].y = centery - vxy + vyy; this.center.x = centerx; this.center.y = centery; this.angle = angle; computeAxes(); extents.x = w / 2; extents.y = h / 2; computeBoundingRect(); } //Updates the axes after the corners move. Assumes the //corners actually form a rectangle. private void computeAxes() { axis[0].x = corner[1].x - corner[0].x; axis[0].y = corner[1].y - corner[0].y; axis[1].x = corner[3].x - corner[0].x; axis[1].y = corner[3].y - corner[0].y; // Make the length of each axis 1/edge length so we know any // dot product must be less than 1 to fall within the edge. for (int a = 0; a < axis.length; ++a) { float l = axis[a].length(); float ll = l * l; axis[a].x = axis[a].x / ll; axis[a].y = axis[a].y / ll; origin[a] = corner[0].dot(axis[a]); } } public void computeBoundingRect() { boundingRect.left = JMath.min(JMath.min(corner[0].x, corner[3].x), JMath.min(corner[1].x, corner[2].x)); boundingRect.top = JMath.min(JMath.min(corner[0].y, corner[1].y),JMath.min(corner[2].y, corner[3].y)); boundingRect.right = JMath.max(JMath.max(corner[1].x, corner[2].x), JMath.max(corner[0].x, corner[3].x)); boundingRect.bottom = JMath.max(JMath.max(corner[2].y, corner[3].y),JMath.max(corner[0].y, corner[1].y)); } public void set(RectF rect) { set(rect.centerX(),rect.centerY(),rect.width(),rect.height(),0.0f); } // Returns true if other overlaps one dimension of this. private boolean overlaps1Way(OBB2D other) { for (int a = 0; a < axis.length; ++a) { double t = other.corner[0].dot(axis[a]); // Find the extent of box 2 on axis a double tMin = t; double tMax = t; for (int c = 1; c < corner.length; ++c) { t = other.corner[c].dot(axis[a]); if (t < tMin) { tMin = t; } else if (t > tMax) { tMax = t; } } // We have to subtract off the origin // See if [tMin, tMax] intersects [0, 1] if ((tMin > 1 + origin[a]) || (tMax < origin[a])) { // There was no intersection along this dimension; // the boxes cannot possibly overlap. return false; } } // There was no dimension along which there is no intersection. // Therefore the boxes overlap. return true; } public void moveTo(float centerx, float centery) { float cx,cy; cx = center.x; cy = center.y; deltaVec.x = centerx - cx; deltaVec.y = centery - cy; for (int c = 0; c < 4; ++c) { corner[c].x += deltaVec.x; corner[c].y += deltaVec.y; } boundingRect.left += deltaVec.x; boundingRect.top += deltaVec.y; boundingRect.right += deltaVec.x; boundingRect.bottom += deltaVec.y; this.center.x = centerx; this.center.y = centery; computeAxes(); } // Returns true if the intersection of the boxes is non-empty. public boolean overlaps(OBB2D other) { if(right() < other.left()) { return false; } if(bottom() < other.top()) { return false; } if(left() > other.right()) { return false; } if(top() > other.bottom()) { return false; } if(other.getAngle() == 0.0f && getAngle() == 0.0f) { return true; } return overlaps1Way(other) && other.overlaps1Way(this); } public Vector2D getCenter() { return center; } public float getWidth() { return extents.x * 2; } public float getHeight() { return extents.y * 2; } public void setAngle(float angle) { set(center.x,center.y,getWidth(),getHeight(),angle); } public float getAngle() { return angle; } public void setSize(float w,float h) { set(center.x,center.y,w,h,angle); } public float left() { return boundingRect.left; } public float right() { return boundingRect.right; } public float bottom() { return boundingRect.bottom; } public float top() { return boundingRect.top; } public RectF getBoundingRect() { return boundingRect; } public boolean overlaps(float left, float top, float right, float bottom) { if(right() < left) { return false; } if(bottom() < top) { return false; } if(left() > right) { return false; } if(top() > bottom) { return false; } return true; } public static float distance(float ax, float ay,float bx, float by) { if (ax < bx) return bx - ay; else return ax - by; } public Vector2D project(float ax, float ay) { projVec.x = Float.MAX_VALUE; projVec.y = Float.MIN_VALUE; for (int i = 0; i < corner.length; ++i) { float dot = Vector2D.dot(corner[i].x,corner[i].y,ax,ay); projVec.x = JMath.min(dot, projVec.x); projVec.y = JMath.max(dot, projVec.y); } return projVec; } public Vector2D getCorner(int c) { return corner[c]; } public int getNumCorners() { return corner.length; } public static float collisionResponse(OBB2D a, OBB2D b, Vector2D outNormal) { float depth = Float.MAX_VALUE; for (int i = 0; i < a.getNumCorners() + b.getNumCorners(); ++i) { Vector2D edgeA; Vector2D edgeB; if(i >= a.getNumCorners()) { edgeA = b.getCorner((i + b.getNumCorners() - 1) % b.getNumCorners()); edgeB = b.getCorner(i % b.getNumCorners()); } else { edgeA = a.getCorner((i + a.getNumCorners() - 1) % a.getNumCorners()); edgeB = a.getCorner(i % a.getNumCorners()); } tempNormal.x = edgeB.x -edgeA.x; tempNormal.y = edgeB.y - edgeA.y; tempNormal.normalize(); projAVec.equals(a.project(tempNormal.x,tempNormal.y)); projBVec.equals(b.project(tempNormal.x,tempNormal.y)); float distance = OBB2D.distance(projAVec.x, projAVec.y,projBVec.x,projBVec.y); if (distance > 0.0f) { return 0.0f; } else { float d = Math.abs(distance); if (d < depth) { depth = d; outNormal.equals(tempNormal); } } } float dx,dy; dx = b.getCenter().x - a.getCenter().x; dy = b.getCenter().y - a.getCenter().y; float dot = Vector2D.dot(dx,dy,outNormal.x,outNormal.y); if(dot > 0) { outNormal.x = -outNormal.x; outNormal.y = -outNormal.y; } return depth; } public Vector2D getMoveDeltaVec() { return deltaVec; } }; Thanks!

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  • PGU Tiles collision detection

    - by user280454
    Hi, I've been using PGU(Phil's Pygame Utilities) for a while. It has a dictionary called tdata, which is passed as an argument while loading tiles tdata = { tileno:(agroup, hit_handler, config)} I'm making a pacman clone in which I have 2 groups : player and ghost, for which I want to collision detection with the same type of tile. For example, if the tile no is 2, I want this tile to have agroups as both player and ghost. I tried doing the following: tdata = {0x02 :('player', tile_hit_1, config), 0x02 : ('ghost', tile_hit_2, config)} However, on doing this, it only gives collision detection for ghost, not the player. Any ideas on how I can do collision detection for both the player and the ghost with the same type of tile?

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  • Are hash collisions with different file sizes just as likely as same file size?

    - by rwmnau
    I'm hashing a large number of files, and to avoid hash collisions, I'm also storing a file's original size - that way, even if there's a hash collision, it's extremely unlikely that the file sizes will also be identical. Is this sound (a hash collision is equally likely to be of any size), or do I need another piece of information (if a collision is more likely to also be the same length as the original). Or, more generally: Is every file just as likely to produce a particular hash, regardless of original file size?

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  • Are has collisions with different file sizes just as likely as same file size?

    - by rwmnau
    I'm hashing a large number of files, and to avoid hash collisions, I'm also storing a file's original size - that way, even if there's a hash collision, it's extrememly unlikely that the file sizes will also be identical. Is this sound (a hash collision is equally likely to be of any size), or do I need another piece of information (if a collision is more likely to also be the same length as the original). Or, more generally: Is every file just as likely to produce a particular hash, regardless of original file size?

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  • Why is mesh baking causing huge performance spikes?

    - by jellyfication
    A couple of seconds into the gameplay on my Android device, I see huge performance spikes caused by "Mesh.Bake Scaled Mesh PhysX CollisionData" In my game, a whole level is a parent object containing multiple ridigbodies with mesh colliders. Every FixedUpdate(), my parent object rotates around the player. Rotating the world causes mesh scaling. Here is the code that handles world rotation. private void Update() { input.update(); Vector3 currentInput = input.GetDirection(); worldParent.rotation = initialRotation; worldParent.DetachChildren(); worldParent.position = transform.position; world.parent = worldParent; worldParent.Rotate(Vector3.right, currentInput.x * 50f); worldParent.Rotate(Vector3.forward, currentInput.z * 50f); } How can I get rid of mesh scaling ? Mesh.Bake physx seems to take effect after some time, is it possible to disable this function ? The profiler looks like this: Bottom-left panel shows data before spikes, the right after

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  • Creating the “game space” for a 2D game

    - by alJaree
    How does one setup the game space for a game so that obstacles can be spawned? One example I am wondering about is doodle jump. Tile maps are limited in size and would need to change often if the user jumps a lot. How would this be done in another way than tile maps. How or what is used to create the notion of a game world where these spawned ledges/obstacles are placed as the user progresses through the stage? What is actually moving if the user jumps from ledge to ledge, what are the ledges based on in terms of the game world/space. What data structure or representation could the game use to reference and manage the spawning of these obstacles/ledges?

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  • Box2D Static-Dynamic body joint eliminates collisions

    - by andrewz
    I have a static body A, and a dynamic body B, and a dynamic body C. A is filtered to not collide with anything, B and C collide with each other. I wish to create a joint between B and A. When I create a joint (ex. revolute), B no longer collides with C - C passes through it as if it does not exist. What am I doing wrong? How can adding a joint prevent a body from colliding with another body it used to? EDIT: I want to join B with A, and have B collide with C, but not A collide with C. In realistic terms, I'm trying to create a revolute joint between a wheel (B) and a wall (A), and have a box (C) hit the wheel and the wheel would then rotate. EDIT: I create a the simplest revolute joint I can with these parameters (C++): b2RevoluteJointDef def; def.Initialize(A, B, B -> GetWorldCenter()); world -> CreateJoint(&def);

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  • How to set a target as image [on hold]

    - by Zadalaxmi
    How to set a target as image in given code. public void addListenerForImage(final Image roomImage) { final DragAndDrop dragAndDrop = new DragAndDrop(); dragAndDrop.addSource(new DragAndDrop.Source(roomImage) { public DragAndDrop.Payload dragStart (InputEvent event, float x, float y, int pointer) { DragAndDrop.Payload payload = new DragAndDrop.Payload(); payload.setDragActor(roomImage); dragAndDrop.setDragActorPosition(-x, -y + roomImage.getHeight()); return payload; } public void dragStop (InputEvent event, float x, float y, int pointer,Target target) { roomImage.setBounds(50, 125, roomImage.getWidth(), roomImage.getHeight()); if(target != null) { roomImage.setPosition(target.getActor().getX(), target.getActor().getY()); } System.out.println(target); stage.addActor(roomImage); } }); My problem is i can drag the images and i am not able to set target as image; and target shows as null;One more if a invisible some of the images in group how can i test that it is overlapped or not;Please give some links and suggestion

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  • Algorithm for spreading labels in a visually appealing and intuitive way

    - by mac
    Short version Is there a design pattern for distributing vehicle labels in a non-overlapping fashion, placing them as close as possible to the vehicle they refer to? If not, is any of the method I suggest viable? How would you implement this yourself? Extended version In the game I'm writing I have a bird-eye vision of my airborne vehicles. I also have next to each of the vehicles a small label with key-data about the vehicle. This is an actual screenshot: Now, since the vehicles could be flying at different altitudes, their icons could overlap. However I would like to never have their labels overlapping (or a label from vehicle 'A' overlap the icon of vehicle 'B'). Currently, I can detect collisions between sprites and I simply push away the offending label in a direction opposite to the otherwise-overlapped sprite. This works in most situations, but when the airspace get crowded, the label can get pushed very far away from its vehicle, even if there was an alternate "smarter" alternative. For example I get: B - label A -----------label C - label where it would be better (= label closer to the vehicle) to get: B - label label - A C - label EDIT: It also has to be considered that beside the overlapping vehicles case, there might be other configurations in which vehicles'labels could overlap (the ASCII-art examples show for example three very close vehicles in which the label of A would overlap the icon of B and C). I have two ideas on how to improve the present situation, but before spending time implementing them, I thought to turn to the community for advice (after all it seems like a "common enough problem" that a design pattern for it could exist). For what it's worth, here's the two ideas I was thinking to: Slot-isation of label space In this scenario I would divide all the screen into "slots" for the labels. Then, each vehicle would always have its label placed in the closest empty one (empty = no other sprites at that location. Spiralling search From the location of the vehicle on the screen, I would try to place the label at increasing angles and then at increasing radiuses, until a non-overlapping location is found. Something down the line of: try 0°, 10px try 10°, 10px try 20°, 10px ... try 350°, 10px try 0°, 20px try 10°, 20px ...

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  • Libgdx detect when player is outside of screen

    - by Rockyy
    Im trying to learn libGDX (coming from XNA/MonoDevelop), and I'm making a super simple test game to get to know it better. I was wondering how to detect if the player sprite is outside of the screen and make it so it is impossible to go outside of the screen edges. In XNA you could do something like this: // Prevent player from moving off the left edge of the screen if (player.Position.X < 0) player.Position = new Vector2(0, player.Position.Y); How is this achieved in libgdx? I think it's the Stage that handles the 2D viewport in libgdx? This is my code so far: private Texture texture; private SpriteBatch batch; private Sprite sprite; @Override public void create () { float w = Gdx.graphics.getWidth(); float h = Gdx.graphics.getHeight(); batch = new SpriteBatch(); texture = new Texture(Gdx.files.internal("player.png")); sprite = new Sprite(texture); sprite.setPosition(w/2 -sprite.getWidth()/2, h/2 - sprite.getHeight()/2); } @Override public void render () { Gdx.gl.glClearColor(1, 1, 1, 1); Gdx.gl.glClear(GL20.GL_COLOR_BUFFER_BIT); if(Gdx.input.isKeyPressed(Input.Keys.LEFT)){ if(Gdx.input.isKeyPressed(Input.Keys.CONTROL_LEFT)) sprite.translateX(-1f); else sprite.translateX(-10.0f); } if(Gdx.input.isKeyPressed(Input.Keys.RIGHT)){ if(Gdx.input.isKeyPressed(Input.Keys.CONTROL_LEFT)) sprite.translateX(1f); else sprite.translateX(10f); } batch.begin(); sprite.draw(batch); batch.end(); }

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  • A* Jump Point Search - how does pruning really work?

    - by DeadMG
    I've come across Jump Point Search, and it seems pretty sweet to me. However, I'm unsure as to how their pruning rules actually work. More specifically, in Figure 1, it states that we can immediately prune all grey neighbours as these can be reached optimally from the parent of x without ever going through node x However, this seems somewhat at odds. In the second image, node 5 could be reached by first going through node 7 and skipping x entirely through a symmetrical path- that is, 6 -> x -> 5 seems to be symmetrical to 6 -> 7 -> 5. This would be the same as how node 3 can be reached without going through x in the first image. As such, I don't understand how these two images are not entirely equivalent, and not just rotated versions of each other. Secondly, I'd like to understand how this algorithm could be generalized to a three-dimensional search volume.

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  • How to impale and stack targets correctly according to the collider and its coordinate?

    - by David Dimalanta
    I'm making another simple game, a catch game, where a spawning target game object must be captured using a skewer to impale it. Here how: At the start, the falling object (in red) will fall in a vertical direction (in blue) When aimed properly, the target will fall down along the line of the skewer. (in blue) Then, another target is spawned and will fall vertically. (in red) When aimed successfully again in a streak, the second target will fall along the skewer and stacked. Same process over and over when another target is spawned. However, when I test run it on the scene tab in Unity, when impaled several targets, instead of a smooth flow and stacking it ended up overlaying it instead of stacking it up like a pancake. Here's what it look like: As I noticed when reaching the half-way of my progress, I tried to figure out how to deal with collider bodies without sticking each other so that it will actually stack like in the example of the image at no. 3. Here's the script code I added in the target game object: using UnityEngine; using System.Collections; public class ImpaleStateTest : MonoBehaviour { public GameObject target; public GameObject skewer; public bool drag = false; private float stack; private float impaleCount; void Start () { stack = 0; impaleCount = 0; } void Update () { if(drag) { target.transform.position = new Vector3 (DragTest.dir.transform.position.x, DragTest.dir.transform.position.y - 0.35f, 0); target.transform.rotation = DragTest.degrees; target.rigidbody2D.fixedAngle = true; target.rigidbody2D.isKinematic = true; target.rigidbody2D.gravityScale = 0; if(Input.GetMouseButton(0)) { Debug.Log ("Skewer: " + DragTest.dir.transform.position.x); Debug.Log ("Target: " + target.transform.position.x); } } } void OnTriggerEnter2D(Collider2D collider) { impaleCount++; Debug.Log ("Impaled " + impaleCount + " time(s)!"); drag = true; audio.Play (); } } Aside from that, I'm not sure if it's right but, the only way to stick the impaled targets while dragging the skewer left or right is to get the X coordinates from the skewer only. Is there something else to recommend it in order to improve this behavior as realistic as possible? Please help.

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  • How do I get the compression on specific dynamic body

    - by Mike JM
    Sorry, I could not find any tag that would suit my question. Let me first show you the image and then write what I want to do: I'm using box2D. As you can see there are three dynamic bodies connected to each other (think of it as a table from front view).The LEG1 and LEG2 are connected to the static body. (it's the ground body). Another dynamic body is falling onto the table. I need to get the compression in the LEG1 and LEG2 separately. Joints have GetReactionForce() function which returns a b2Vec, which in turn has Length() and LengthSqd functions. This will give the total sum of the forces in any taken joint. But what I need is forces in individual bodies that are connected with joints. Once you connect several bodies with a single joint it again will show the sum of forces which is not useful.Here's the case iI'm talking about:

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  • How to do reflective collisions with particles hitting background tiles?

    - by Shawn LeBlanc
    In my 2d pixel old-school platformer, I'm looking for methods for bouncing particles off of background tiles. Particles aren't affected by gravity and collisions are "reflective". By that I mean a particle hitting the side of a square tile at 45 degrees should bounce off at 45 degrees as well. We can assume that tiles will always be perfectly square. No slopes or anything. What are efficient methods and algorithms to do this? I'd be implementing this on a Sega Genesis.

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  • problem with frustum AABB culling in DirectX

    - by Matthew Poole
    Hi, I am currently working on a project with a few friends, and I am trying to get frustum culling working. Every single tutorial or article I go to shows that my math is correct and that this should be working. I thought maybe posting here, somebody would catch something I could not. Thank you. Here are the important code snippets /create the projection matrix void CD3DCamera::SetLens(float fov, float aspect, float nearZ, float farZ) { D3DXMatrixPerspectiveFovLH(&projMat, D3DXToRadian(fov), aspect, nearZ, farZ); } //build the view matrix after changes have been made to camera void CD3DCamera::BuildView() { //keep axes orthoganal D3DXVec3Normalize(&look, &look); //up D3DXVec3Cross(&up, &look, &right); D3DXVec3Normalize(&up, &up); //right D3DXVec3Cross(&right, &up, &look); D3DXVec3Normalize(&right, &right); //fill view matrix float x = -D3DXVec3Dot(&position, &right); float y = -D3DXVec3Dot(&position, &up); float z = -D3DXVec3Dot(&position, &look); viewMat(0,0) = right.x; viewMat(1,0) = right.y; viewMat(2,0) = right.z; viewMat(3,0) = x; viewMat(0,1) = up.x; viewMat(1,1) = up.y; viewMat(2,1) = up.z; viewMat(3,1) = y; viewMat(0,2) = look.x; viewMat(1,2) = look.y; viewMat(2,2) = look.z; viewMat(3,2) = z; viewMat(0,3) = 0.0f; viewMat(1,3) = 0.0f; viewMat(2,3) = 0.0f; viewMat(3,3) = 1.0f; } void CD3DCamera::BuildFrustum() { D3DXMATRIX VP; D3DXMatrixMultiply(&VP, &viewMat, &projMat); D3DXVECTOR4 col0(VP(0,0), VP(1,0), VP(2,0), VP(3,0)); D3DXVECTOR4 col1(VP(0,1), VP(1,1), VP(2,1), VP(3,1)); D3DXVECTOR4 col2(VP(0,2), VP(1,2), VP(2,2), VP(3,2)); D3DXVECTOR4 col3(VP(0,3), VP(1,3), VP(2,3), VP(3,3)); // Planes face inward frustum[0] = (D3DXPLANE)(col2); // near frustum[1] = (D3DXPLANE)(col3 - col2); // far frustum[2] = (D3DXPLANE)(col3 + col0); // left frustum[3] = (D3DXPLANE)(col3 - col0); // right frustum[4] = (D3DXPLANE)(col3 - col1); // top frustum[5] = (D3DXPLANE)(col3 + col1); // bottom // Normalize the frustum for( int i = 0; i < 6; ++i ) D3DXPlaneNormalize( &frustum[i], &frustum[i] ); } bool FrustumCheck(D3DXVECTOR3 max, D3DXVECTOR3 min, const D3DXPLANE* frustum) { // Test assumes frustum planes face inward. D3DXVECTOR3 P; D3DXVECTOR3 Q; bool ret = false; for(int i = 0; i < 6; ++i) { // For each coordinate axis x, y, z... for(int j = 0; j < 3; ++j) { // Make PQ point in the same direction as the plane normal on this axis. if( frustum[i][j] > 0.0f ) { P[j] = min[j]; Q[j] = max[j]; } else { P[j] = max[j]; Q[j] = min[j]; } } if(D3DXPlaneDotCoord(&frustum[i], &Q) < 0.0f ) ret = false; } return true; }

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  • Finding Z given X & Y coordinates on terrain?

    - by mrky
    I need to know what the most efficient way of finding Z given X & Y coordinates on terrain. My terrain is set up as a grid, each grid block consisting of two triangles, which may be flipped in any direction. I want to move game objects smoothly along the floor of the terrain without "stepping." I'm currently using the following method with unexpected results: double mapClass::getZ(double x, double y) { int vertexIndex = ((floor(y))*width*2)+((floor(x))*2); vec3ray ray = {glm::vec3(x, y, 2), glm::vec3(x, y, 0)}; vec3triangle tri1 = { glmFrom(vertices[vertexIndex].v1), glmFrom(vertices[vertexIndex].v2), glmFrom(vertices[vertexIndex].v3) }; vec3triangle tri2 = { glmFrom(vertices[vertexIndex+1].v1), glmFrom(vertices[vertexIndex+1].v2), glmFrom(vertices[vertexIndex+1].v3) }; glm::vec3 intersect; if (!intersectRayTriangle(tri1, ray, intersect)) { intersectRayTriangle(tri2, ray, intersect); } return intersect.z; } intersectRayTriangle() and glmFrom() are as follows: bool intersectRayTriangle(vec3triangle tri, vec3ray ray, glm::vec3 &worldIntersect) { glm::vec3 barycentricIntersect; if (glm::intersectLineTriangle(ray.origin, ray.direction, tri.p0, tri.p1, tri.p2, barycentricIntersect)) { // Convert barycentric to world coordinates double u, v, w; u = barycentricIntersect.x; v = barycentricIntersect.y; w = 1 - (u+v); worldIntersect.x = (u * tri.p0.x + v * tri.p1.x + w * tri.p2.x); worldIntersect.y = (u * tri.p0.y + v * tri.p1.y + w * tri.p2.y); worldIntersect.z = (u * tri.p0.z + v * tri.p1.z + w * tri.p2.z); return true; } else { return false; } } glm::vec3 glmFrom(s_point3f point) { return glm::vec3(point.x, point.y, point.z); } My convenience structures are defined as: struct s_point3f { GLfloat x, y, z; }; struct s_triangle3f { s_point3f v1, v2, v3; }; struct vec3ray { glm::vec3 origin, direction; }; struct vec3triangle { glm::vec3 p0, p1, p2; }; vertices is defined as: std::vector<s_triangle3f> vertices; Basically, I'm trying to get the intersect of a ray (which is positioned at the x, and y coordinates specified facing pointing downwards toward the terrain) and one of the two triangles on the grid. getZ() rarely returns anything but 0. Other times, the numbers it generates seem to be completely off. Am I taking the wrong approach? Can anyone see a problem with my code? Any help or critique is appreciated!

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  • 2D object-aligned bounding-box intersection test

    - by AshleysBrain
    Hi all, I have two object-aligned bounding boxes (i.e. not axis aligned, they rotate with the object). I'd like to know if two object-aligned boxes overlap. (Edit: note - I'm using an axis-aligned bounding box test to quickly discard distant objects, so it doesn't matter if the quad routine is a little slower.) My boxes are stored as four x,y points. I've searched around for answers, but I can't make sense of the variable names and algorithms in examples to apply them to my particular case. Can someone help show me how this would be done, in a clear and simple way? Thanks. (The particular language isn't important, C-style pseudo code is OK.)

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  • Calculating 2D (screen) coordinates from 3D positions in XNA 4.0

    - by NDraskovic
    I have a program that draws some items to the scene by loading their positions from a file. Now I want to place a Ray on the same location where the items are drawn. So my question is how can I calculate the position of the ray (it's 2D components) by using 3D coordinates of each particular item? The items don't move anywhere, so once they are placed they stay until the end of the programs execution. Thanks.

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  • Platform jumping problems with AABB collisions

    - by Vee
    See the diagram first: When my AABB physics engine resolves an intersection, it does so by finding the axis where the penetration is smaller, then "push out" the entity on that axis. Considering the "jumping moving left" example: If velocityX is bigger than velocityY, AABB pushes the entity out on the Y axis, effectively stopping the jump (result: the player stops in mid-air). If velocityX is smaller than velocitY (not shown in diagram), the program works as intended, because AABB pushes the entity out on the X axis. How can I solve this problem? Source code: public void Update() { Position += Velocity; Velocity += World.Gravity; List<SSSPBody> toCheck = World.SpatialHash.GetNearbyItems(this); for (int i = 0; i < toCheck.Count; i++) { SSSPBody body = toCheck[i]; body.Test.Color = Color.White; if (body != this && body.Static) { float left = (body.CornerMin.X - CornerMax.X); float right = (body.CornerMax.X - CornerMin.X); float top = (body.CornerMin.Y - CornerMax.Y); float bottom = (body.CornerMax.Y - CornerMin.Y); if (SSSPUtils.AABBIsOverlapping(this, body)) { body.Test.Color = Color.Yellow; Vector2 overlapVector = SSSPUtils.AABBGetOverlapVector(left, right, top, bottom); Position += overlapVector; } if (SSSPUtils.AABBIsCollidingTop(this, body)) { if ((Position.X >= body.CornerMin.X && Position.X <= body.CornerMax.X) && (Position.Y + Height/2f == body.Position.Y - body.Height/2f)) { body.Test.Color = Color.Red; Velocity = new Vector2(Velocity.X, 0); } } } } } public static bool AABBIsOverlapping(SSSPBody mBody1, SSSPBody mBody2) { if(mBody1.CornerMax.X <= mBody2.CornerMin.X || mBody1.CornerMin.X >= mBody2.CornerMax.X) return false; if (mBody1.CornerMax.Y <= mBody2.CornerMin.Y || mBody1.CornerMin.Y >= mBody2.CornerMax.Y) return false; return true; } public static bool AABBIsColliding(SSSPBody mBody1, SSSPBody mBody2) { if (mBody1.CornerMax.X < mBody2.CornerMin.X || mBody1.CornerMin.X > mBody2.CornerMax.X) return false; if (mBody1.CornerMax.Y < mBody2.CornerMin.Y || mBody1.CornerMin.Y > mBody2.CornerMax.Y) return false; return true; } public static bool AABBIsCollidingTop(SSSPBody mBody1, SSSPBody mBody2) { if (mBody1.CornerMax.X < mBody2.CornerMin.X || mBody1.CornerMin.X > mBody2.CornerMax.X) return false; if (mBody1.CornerMax.Y < mBody2.CornerMin.Y || mBody1.CornerMin.Y > mBody2.CornerMax.Y) return false; if(mBody1.CornerMax.Y == mBody2.CornerMin.Y) return true; return false; } public static Vector2 AABBGetOverlapVector(float mLeft, float mRight, float mTop, float mBottom) { Vector2 result = new Vector2(0, 0); if ((mLeft > 0 || mRight < 0) || (mTop > 0 || mBottom < 0)) return result; if (Math.Abs(mLeft) < mRight) result.X = mLeft; else result.X = mRight; if (Math.Abs(mTop) < mBottom) result.Y = mTop; else result.Y = mBottom; if (Math.Abs(result.X) < Math.Abs(result.Y)) result.Y = 0; else result.X = 0; return result; }

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  • How would I be able to get a game over screen using the pause function?

    - by Joachim Velzel
    I am having problems with my snake game, when the snake collides with itself it draws a "game over" image in the background, but only while it's colliding with itself. I want it to behave like the pause function, so that as soon as the snake collides with itself it draws an image on the screen and stops the game play. And then how would you be able to restart or to quit the game? I just have this for the detection at the moment: if (snakeHeadRectangle.Intersects(snakeBodyRectangleArray[bodyNumber])) { spriteBatch.Draw(textureGameOver, gameOverPosition, Color.White); } Thanks

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