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• Scaling along an arbitrary axis (Dealing with non-uniform scale)

  - by Jon

  I'm trying to build my own little engine to get more familiar with the concepts of 3D programming. I have a transform class that on each frame it creates a Scaling Matrix (S), a Rotation Matrix from a Quaternion (R) and concatenates them together (S*R). Once i have SR, I insert the translation values into the bottom of the three columns. So i end up with a transformation matrix that looks like: [SR SR SR 0] [SR SR SR 0] [SR SR SR 0] [tx ty tz 1] This works perfectly in all cases except when rotating an object that has a non-uniform scale. For example a unit cube with ScaleX = 4, ScaleY = 2, ScaleZ = 1 will give me a rectangular box that is 4 times as wide as the depth and twice as high as the depth. If i then translate this around, the box stays the same and looks normal. The problem happens whenever I try to rotate this scaled box. The shape itself becomes distorted and it appears as though the Scale factors are affecting the object on the World X,Y,Z axis rather than the local X,Y,Z axis of the object. I've done some pretty extensive research through a variety of textbooks (Eberly, Moller/Hoffman, Phar etc) and there isn't a ton there to go off of. Online, most of the answers say to avoid non-uniform scaling which I understand the desire to avoid it, but I'd still like to figure out how to support it. The only thing I can think off is that when constructing a Scale Matrix: [sx 0 0 0] [0 sy 0 0] [0 0 sz 0] [0 0 0 1] This is scaling along the World Axis instead of the object's local Direction, Up and Right vectors or it's local Z, Y, X axis. Does anyone have any tips or ideas on how to handle construction a transformation matrix that allows for non-uniform scaling and rotation? Thanks!

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• Maya Animated Character export for XNA 4.0 problem

  - by FahidK

  To begin with, I'm trying to export an animated character in .fbx format from Maya 2013 to XNA 4.0 In Maya, The Model has a basic rig and the animations are in clips made in the Trax editor. so the issue i'm having is after selecting the model and the root joint and then hitting export in .fbx format, for some reason when i open the exported .fbx file the joint system is detached from the model with no animation. Btw, i have the animations in clips so that they can be called in code, for example "run","walk","attack". So, what can i do to solve this problem? Thank you.

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• Where to start? (3D Modeling)

  - by herfus

  I'm looking for a good resource to start learning 3d modeling. I'm looking for something that starts with the basics (e.g. terminology; what are quads, triangles etc.) before/while going into the actual modeling. Book, website, video, anything will do. I'm only concerned with the quality of the tutorials, how thorough they are. I have experience with texturing, level design and so on - but I've never created anything more than simple shapes/editing existing assets.

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• Is there a way to use the facebook sdk with libgdx?

  - by Rudy_TM

  I have tried to use the facebook sdk in libgdx with callbacks, but it never enters the authetication listeners, so the user never is logged in, it permits the authorization for the facebook app but it never implements the authentication interfaces :( Is there a way to use it? public MyFbClass() { facebook = new Facebook(APPID); mAsyncRunner = new AsyncFacebookRunner(facebook); SessionStore.restore(facebook, this); FB.init(this, 0, facebook, this.permissions); } ///Method for init the permissions and my listener for authetication public void init(final Activity activity, final Facebook fb,final String[] permissions) { mActivity = activity; this.fb = fb; mPermissions = permissions; mHandler = new Handler(); async = new AsyncFacebookRunner(mFb); params = new Bundle(); SessionEvents.addAuthListener(auth); } ///I call the authetication process, I call it with a callback from libgdx public void facebookAction() { // TODO Auto-generated method stub fb.authenticate(); } ///It only allow the app permission, it doesnt register the events public void authenticate() { if (mFb.isSessionValid()) { SessionEvents.onLogoutBegin(); AsyncFacebookRunner asyncRunner = new AsyncFacebookRunner(mFb); asyncRunner.logout(getContext(), new LogoutRequestListener()); //SessionStore.save(this.mFb, getContext()); } else { mFb.authorize(mActivity, mPermissions,0 , new DialogListener()); } } public class SessionListener implements AuthListener, LogoutListener { @Override public void onAuthSucceed() { SessionStore.save(mFb, getContext()); } @Override public void onAuthFail(String error) { } @Override public void onLogoutBegin() { } @Override public void onLogoutFinish() { SessionStore.clear(getContext()); } } DialogListener() { @Override public void onComplete(Bundle values) { SessionEvents.onLoginSuccess(); } @Override public void onFacebookError(FacebookError error) { SessionEvents.onLoginError(error.getMessage()); } @Override public void onError(DialogError error) { SessionEvents.onLoginError(error.getMessage()); } @Override public void onCancel() { SessionEvents.onLoginError("Action Canceled"); } }

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• Behaviour tree code example?

  - by jokoon

  http://altdevblogaday.org/2011/02/24/introduction-to-behavior-trees/ Obviously the most interesting article I found on this website. What do you think about it ? It lacks some code example, don't you know any ? I also read that state machines are not very flexible compared to behaviour trees... On top of that I'm not sure if there is a true link between state machines and the state pattern... is there ?

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• Java: Reflection Packet Builder using getField()

  - by Matchlighter

  So I just finished writing a packet builder that dynamically loads data into a data stream which is then sent out. Each builder operates by finding fields in its class (and its superclasses) that are marked with an @data annotation. Upon finishing the builder, I remembered that getFields() does not return in "any specific order". I quite like my builder because it allows for quite simple, yet hard-typed packets. Could this implementation be a problem? What would be the best next step to keep the simplicity - do alphabetical sorting of fields?

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• Isometric algorithm [fixed]

  - by David

  so i've been toying with isometric and i just cant get the tiles to be in the right order. im probably missing something obvious and i just cant see it... but even at the risk of looking stupid, heres my code. for (int i = 0; i < Tile.MapSize; i++) { for (int j = 0; j < Tile.MapSize; j++) { spriteBatch.Draw( Tile.TileSetTexture, new Rectangle( (-j * Tile.TileWidth / 2) + (i * Tile.TileWidth / 2), (i * (Tile.TileHeight - 9) / 2) - (-j * (Tile.TileHeight - 9) / 2), Tile.TileWidth, Tile.TileHeight), Tile.GetSourceRectangle(tileID), Color.White, 0.0f, new Vector2(-350, -60), SpriteEffects.None, 1.0f); } } and heres what i end up with delicious messed up map yep, bit of an issue. so if anyone could help, i'd appreciate it. edit* works now <_<

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• How does a collision engine work?

  - by JXPheonix

  Original question: Click me How exactly does a collision engine work? This is an extremely broad question. What code keeps things bouncing against each other, what code makes the player walk into a wall instead of walk through the wall? How does the code constantly refresh the players position and objects position to keep gravity and collision working as it should? If you don't know what a collision engine is, basically it's generally used in platform games to make the player acutally hit walls and the like. There's the 2D type and the 3D type, but they all accomplish the same thing: collision. So, what keeps a collision engine ticking?

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• How to create a copy of an instance without having access to private variables

  - by Jamie

  Im having a bit of a problem. Let me show you the code first: public class Direction { private CircularList xSpeed, zSpeed; private int[] dirSquare = {-1, 0, 1, 0}; public Direction(int xSpeed, int zSpeed){ this.xSpeed = new CircularList(dirSquare, xSpeed); this.zSpeed = new CircularList(dirSquare, zSpeed); } public Direction(Point dirs){ this(dirs.x, dirs.y); } public void shiftLeft(){ xSpeed.shiftLeft(); zSpeed.shiftRight(); } public void shiftRight(){ xSpeed.shiftRight(); zSpeed.shiftLeft(); } public int getXSpeed(){ return this.xSpeed.currentValue(); } public int getZSpeed(){ return this.zSpeed.currentValue(); } } Now lets say i have an instance of Direction: Direction dir = new Direction(0, 0); As you can see in the code of Direction, the arguments fed to the constructor, are passed directly to some other class. One cannot be sure if they stay the same because methods shiftRight() and shiftLeft could have been called, which changes thos numbers. My question is, how do i create a completely new instance of Direction, that is basically copy(not by reference) of dir? The only way i see it, is to create public methods in both CircularList(i can post the code of this class, but its not relevant) and Direction that return the variables needed to create a copy of the instance, but this solution seems really dirty since those numbers are not supposed to be touched after beeing fed to the constructor, and therefore they are private.

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• Making body(box2d) a spite(andengine) in android

  - by Kadir

  I can't make body(box2d) a spite(andengine) and at the same time i wanna apply MoveModifier to sprite which is body.if i can make just body,it works namely the srites can collide.if i can apply just MoveModifier to sprites,the sprites can move where i want.but i wanna make body(they can collide) and apply MoveModifier(they can move where i want) at the same time.How can i do? this my code just run MoveModifier not as body at the same time. circles[i] = new Sprite(startX, startY, textRegCircle[i]); body[i] = PhysicsFactory.createCircleBody(physicsWorld, circles[i], BodyType.DynamicBody, FIXTURE_DEF); physicsWorld.registerPhysicsConnector(new PhysicsConnector(circles[i], body[i], true, true)); circles[i].registerEntityModifier( (IEntityModifier) new SequenceEntityModifier ( new MoveModifier(10.0f, circles[i].getX(), circles[i].getX(), circles[i].getY(),CAMERA_HEIGHT+64.0f))); scene.getLastChild().attachChild(circles[i]); scene.registerUpdateHandler(physicsWorld);

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• Sorting objects before rendering

  - by dreta

  I'm trying to implement a scene graph and in all the articles i've come across there is talk about object sorting. So you'd sort your objects by "material" for example. Now untill i sat down and started implementing it, i kind of took this for granted, because it made sense. But now i'm wondering what does sorting actually change? In my engine, i have a manager for UBOs, i use those to store data that'll be shared between programs, at the moment that only involves time, camera and projection matrices and lights (i'm not worrying about managing which lights affect which objects ATM). Now for each model i have to change the model to world matrix uniform, no sorting is going to change that. So is the jump from changing this matrix to also setting a material for each object that bad? I vaguely remember reading somewhere that each time you change something in the pipeline, it has to get flushed and that can cause performance issues. But for each drawing call i'm setting up a model to world matrix anyway, so what sense does it make to ever be concerned about this? BTW is there any information about whether changing a uniform and calling glBufferSubData is more (or less) expensive.

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• Quaternion LookAt for camera

  - by Homar

  I am using the following code to rotate entities to look at points. glm::vec3 forwardVector = glm::normalize(point - position); float dot = glm::dot(glm::vec3(0.0f, 0.0f, 1.0f), forwardVector); float rotationAngle = (float)acos(dot); glm::vec3 rotationAxis = glm::normalize(glm::cross(glm::vec3(0.0f, 0.0f, 1.0f), forwardVector)); rotation = glm::normalize(glm::quat(rotationAxis * rotationAngle)); This works fine for my usual entities. However, when I use this on my Camera entity, I get a black screen. If I flip the subtraction in the first line, so that I take the forward vector to be the direction from the point to my camera's position, then my camera works but naturally my entities rotate to look in the opposite direction of the point. I compute the transformation matrix for the camera and then take the inverse to be the View Matrix, which I pass to my OpenGL shaders: glm::mat4 viewMatrix = glm::inverse( cameraTransform->GetTransformationMatrix() ); The orthographic projection matrix is created using glm::ortho. What's going wrong?

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• Drawing 2D Grid in 3D View - Need help with method

  - by Deukalion

  I'm trying to draw a simple 2D grid for an editor, to able to navigate more clearly around the 3D space, but I can't render it: Grid2D class, creates a grid of a certain size at a location and should just draw lines. public class Grid2D : IShape { private VertexPositionColor[] _vertices; private Vector2 _size; private Vector3 _location; private int _faces; public Grid2D(Vector2 size, Vector3 location, Color color) { float x = 0, y = 0; if (size.X < 1f) { size.X = 1f; } if (size.Y < 1f) { size.Y = 1f; } _size = size; _location = location; List<VertexPositionColor> vertices = new List<VertexPositionColor>(); _faces = 0; for (y = -size.Y; y <= size.Y; y++) { vertices.Add(new VertexPositionColor(location + new Vector3(-size.X, y, 0), color)); vertices.Add(new VertexPositionColor(location + new Vector3(size.X, y, 0), color)); _faces++; } for (x = -size.X; x <= size.X; x++) { vertices.Add(new VertexPositionColor(location + new Vector3(x, -size.Y, 0), color)); vertices.Add(new VertexPositionColor(location + new Vector3(x, size.Y, 0), color)); _faces++; } _vertices = vertices.ToArray(); } public void Render(GraphicsDevice device) { device.DrawUserPrimitives<VertexPositionColor>(PrimitiveType.LineList, _vertices, 0, _faces); } } Like this: +----+----+----+----+ | | | | | +----+----+----+----+ | | | | | +----+----+----+----+ | | | | | +----+----+----+----+ | | | | | +----+----+----+----+ Anyone knows what I'm doing wrong? If I add a Shape without texture, it's set automatically to VertexColorEnabled and TextureEnabled = false. This is how I render it: foreach (RenderObject render in _renderObjects) { render.Effect.Projection = projection; render.Effect.View = view; render.Effect.World = world; foreach (EffectPass pass in render.Effect.CurrentTechnique.Passes) { pass.Apply(); try { // Could be a Grid2D render.Shape.Render(_device); } catch { throw; } } } Exception is thrown: The current vertex shader declaration does not include all the elements required by the current Vertex Shader. Normal0 is missing. Simply put, I can't figure out how to draw a few lines. I want to draw them one at a time and I guess that's the problem I haven't figured out, and even when I tried rendering vertices[i], vertices[i+1] and primitiveCount = 1, vertices = 2, and so on it didn't work either. Any suggestions?

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• Drawing texture does not work anymore with a small amount of triangles

  - by Paul

  When i draw lines, the vertices are well connected. But when i draw the texture inside the triangles, it only works with i<4 in the for loop, otherwise with i<5 for example, there is a EXC_BAD_ACCESS message, at @synthesize textureImage = _textureImage. I don't understand why. (The generatePolygons method seems to work fine as i tried to draw lines with many vertices as in the second image below. And textureImage remains the same for i<4 or i<5 : it's a 512px square image). Here are the images : What i want to achieve is to put the red points and connect them to the y-axis (the green points) and color the area (the green triangles) : If i only draw lines, it works fine : Then with a texture color, it works for i<4 in the loop (the red points in my first image, plus the fifth one to connect the last y) : But then, if i set i<5, the debug tool says EXC_BAD_ACCESS at the synthesize of _textureImage. Here is my code : I set a texture color in HelloWordLayer.mm with : CCSprite *textureImage = [self spriteWithColor:color3 textureSize:512]; _terrain.textureImage = textureImage; Then in the class Terrain, i create the vertices and put the texture in the draw method : @implementation Terrain @synthesize textureImage = _textureImage; //EXC_BAD_ACCESS for i<5 - (void)generatePath2{ CGSize winSize = [CCDirector sharedDirector].winSize; float x = 40; float y = 0; for(int i = 0; i < kMaxKeyPoints+1; ++i) { _hillKeyPoints[i] = CGPointMake(x, y); x = 150 + (random() % (int) 30); y += 30; } } -(void)generatePolygons{ _nPolyVertices = 0; float x1 = 0; float y1 = 0; int keyPoints = 0; for (int i=0; i<4; i++){ /* HERE : 4 = OK / 5 = crash */ //V0: at (0,0) _polyVertices[_nPolyVertices] = CGPointMake(x1, y1); _polyTexCoords[_nPolyVertices++] = CGPointMake(x1, y1); //V1: to the first "point" _polyVertices[_nPolyVertices] = CGPointMake(_hillKeyPoints[keyPoints].x, _hillKeyPoints[keyPoints].y); _polyTexCoords[_nPolyVertices++] = CGPointMake(_hillKeyPoints[keyPoints].x, _hillKeyPoints[keyPoints].y); keyPoints++; //from point at index 0 to 1 //V2, same y as point n°2: _polyVertices[_nPolyVertices] = CGPointMake(0, _hillKeyPoints[keyPoints].y); _polyTexCoords[_nPolyVertices++] = CGPointMake(0, _hillKeyPoints[keyPoints].y); //V1 again _polyVertices[_nPolyVertices] = _polyVertices[_nPolyVertices-2]; _polyTexCoords[_nPolyVertices++] = _polyVertices[_nPolyVertices-2]; //V2 again _polyVertices[_nPolyVertices] = _polyVertices[_nPolyVertices-2]; _polyTexCoords[_nPolyVertices++] = _polyVertices[_nPolyVertices-2]; //V3 = same x,y as point at index 1 _polyVertices[_nPolyVertices] = CGPointMake(_hillKeyPoints[keyPoints].x, _hillKeyPoints[keyPoints].y); _polyTexCoords[_nPolyVertices] = CGPointMake(_hillKeyPoints[keyPoints].x, _hillKeyPoints[keyPoints].y); y1 = _polyVertices[_nPolyVertices].y; _nPolyVertices++; } } - (id)init { if ((self = [super init])) { [self generatePath2]; [self generatePolygons]; } return self; } - (void) draw { //glDisable(GL_TEXTURE_2D); glDisableClientState(GL_COLOR_ARRAY); glDisableClientState(GL_TEXTURE_COORD_ARRAY); glBindTexture(GL_TEXTURE_2D, _textureImage.texture.name); glColor4f(1, 1, 1, 1); glVertexPointer(2, GL_FLOAT, 0, _polyVertices); glTexCoordPointer(2, GL_FLOAT, 0, _polyTexCoords); glDrawArrays(GL_TRIANGLE_STRIP, 0, (GLsizei)_nPolyVertices); glColor4f(1, 1, 1, 1); for(int i = 1; i < 40; ++i) { ccDrawLine(_polyVertices[i-1], _polyVertices[i]); } // restore default GL states glEnable(GL_TEXTURE_2D); glEnableClientState(GL_COLOR_ARRAY); glEnableClientState(GL_TEXTURE_COORD_ARRAY); } Do you see anything wrong in this code? Thanks for your help

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• How to make room reflection using Cubemap

  - by MaT

  I am trying to use a cube map of the inside of a room to create some reflections on walls, ceiling and floor. But when I use the cube map, the reflected image is not correct. The point of view seems to be false. To be correct I use a different cube map for each walls, floor or ceiling. The cube map is calculated from the center of the plane looking at the room. Are there specialized techniques to achieve such effect ? Thanks a lot !

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• Suggestions to start a cross-platform project

  - by Gabriele

  I have a big project in my head, it should be cross-platform (Win, Max and Linux), online (Client - Server) and with 3D graphics. I would like some suggestions to start with the right things. Currently I'm a PHP/MySQL coder, I used to code in C and Pascal on DOS ages (Borland Times ;)), my C knowlegde need a refresh but it's ok. I guess C++ it's the right language. What platform and what i should use to code? I can choose from all three platforms. My idea was to use Visual Studio 2010 C++, but i'm not sure if it support Native code. What kind of libraries should i use? I guessed OpenSSL for the login, OpenGL for graphics part. For the Audio or the GUI? Any other suggestions are well accepted. I know it's a "BIG DEAL" but I have no rush and it'll be a free-time project, only for my pleasure. Thank you in advance.

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• The purpose of using invert and transpose

  - by user699215

  In openGl ES and the World of 3D - why use the invers matrix? The thing is that I dont have any intuition to, why it is used, therefore please correct me: As fare as I understand, it is used in shaders - and can help you to figure out the opposite direction of the normals? Invers in ordinary numbers is like; The product of a number and its multiplicative inverse is 1. Observe that 3/5 * 5/3 = 1. In a matrix this will give you the Identity Matrix, which is the base coordinate system or the orion of the World space - right. But the invers is - some other coordinate system? You can use the transpose(Row-major order to Column-major order) of a square matrix to find the inverted matrix, as calculating the invers is process heavy - and the transpose is giving you the inverted matrix as a bi product? Again, I am looking for getting some intuition of this - and therefore be able to use it as intended. Thank you for any reply that will guide me in the right direction. Regards

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• Collision Detection problems in Voxel Engine (XNA)

  - by Darestium

  I am creating a minecraft like terrain engine in XNA and have had some collision problems for quite some time. I have checked and changed my code based on other peoples collision code and I still have the same problem. It always seems to be off by about a block. for instance, if I walk across a bridge which is one block high I fall through it. Also, if you walk towards a "row" of blocks like this: You are able to stand "inside" the left most one, and you collide with nothing in the right most side (where there is no block and is not visible on this image). Here is all my collision code: private void Move(GameTime gameTime, Vector3 direction) { float speed = playermovespeed * (float)gameTime.ElapsedGameTime.TotalSeconds; Matrix rotationMatrix = Matrix.CreateRotationY(player.Camera.LeftRightRotation); Vector3 rotatedVector = Vector3.Transform(direction, rotationMatrix); rotatedVector.Normalize(); Vector3 testVector = rotatedVector; testVector.Normalize(); Vector3 movePosition = player.position + testVector * speed; Vector3 midBodyPoint = movePosition + new Vector3(0, -0.7f, 0); Vector3 headPosition = movePosition + new Vector3(0, 0.1f, 0); if (!world.GetBlock(movePosition).IsSolid && !world.GetBlock(midBodyPoint).IsSolid && !world.GetBlock(headPosition).IsSolid) { player.position += rotatedVector * speed; } //player.position += rotatedVector * speed; } ... public void UpdatePosition(GameTime gameTime) { player.velocity.Y += playergravity * (float)gameTime.ElapsedGameTime.TotalSeconds; Vector3 footPosition = player.Position + new Vector3(0f, -1.5f, 0f); Vector3 headPosition = player.Position + new Vector3(0f, 0.1f, 0f); // If the block below the player is solid the Y velocity should be zero if (world.GetBlock(footPosition).IsSolid || world.GetBlock(headPosition).IsSolid) { player.velocity.Y = 0; } UpdateJump(gameTime); UpdateCounter(gameTime); ProcessInput(gameTime); player.Position = player.Position + player.velocity * (float)gameTime.ElapsedGameTime.TotalSeconds; velocity = Vector3.Zero; } and the one and only function in the camera class: protected void CalculateView() { Matrix rotationMatrix = Matrix.CreateRotationX(upDownRotation) * Matrix.CreateRotationY(leftRightRotation); lookVector = Vector3.Transform(Vector3.Forward, rotationMatrix); cameraFinalTarget = Position + lookVector; Vector3 cameraRotatedUpVector = Vector3.Transform(Vector3.Up, rotationMatrix); viewMatrix = Matrix.CreateLookAt(Position, cameraFinalTarget, cameraRotatedUpVector); } which is called when the rotation variables are changed: public float LeftRightRotation { get { return leftRightRotation; } set { leftRightRotation = value; CalculateView(); } } public float UpDownRotation { get { return upDownRotation; } set { upDownRotation = value; CalculateView(); } } World class: public Block GetBlock(int x, int y, int z) { if (InBounds(x, y, z)) { Vector3i regionalPosition = GetRegionalPosition(x, y, z); Vector3i region = GetRegionPosition(x, y, z); return regions[region.X, region.Y, region.Z].Blocks[regionalPosition.X, regionalPosition.Y, regionalPosition.Z]; } return new Block(BlockType.none); } public Vector3i GetRegionPosition(int x, int y, int z) { int regionx = x == 0 ? 0 : x / Variables.REGION_SIZE_X; int regiony = y == 0 ? 0 : y / Variables.REGION_SIZE_Y; int regionz = z == 0 ? 0 : z / Variables.REGION_SIZE_Z; return new Vector3i(regionx, regiony, regionz); } public Vector3i GetRegionalPosition(int x, int y, int z) { int regionx = x == 0 ? 0 : x / Variables.REGION_SIZE_X; int X = x % Variables.REGION_SIZE_X; int regiony = y == 0 ? 0 : y / Variables.REGION_SIZE_Y; int Y = y % Variables.REGION_SIZE_Y; int regionz = z == 0 ? 0 : z / Variables.REGION_SIZE_Z; int Z = z % Variables.REGION_SIZE_Z; return new Vector3i(X, Y, Z); } Any ideas how to fix this problem? EDIT 1: Graphic of the problem: EDIT 2 GetBlock, Vector3 version: public Block GetBlock(Vector3 position) { int x = (int)Math.Floor(position.X); int y = (int)Math.Floor(position.Y); int z = (int)Math.Ceiling(position.Z); Block block = GetBlock(x, y, z); return block; } Now, the thing is I tested the theroy that the Z is always "off by one" and by ceiling the value it actually works as intended. Altough it still could be greatly more accurate (when you go down holes you can see through the sides, and I doubt it will work with negitive positions). I also does not feel clean Flooring the X and Y values and just Ceiling the Z. I am surely not doing something correctly still.

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• Moving objects colliding when using unalligned collision avoidance (steering)

  - by James Bedford

  I'm having trouble with unaligned collision avoidance for what I think is a rare case. I have set two objects to move towards each other but with a slight offset, so one of the objects is moving slightly upwards, and one of the objects is moving slightly downwards. In my unaligned collision avoidance steering algorithm I'm finding the points on the object's forward line and the other object's forward line where these two lines are the closest. If these closest points are within a collision avoidance distance, and if the distance between them is smaller than the two radii of the two object's bounding spheres, then the objects should steer away in the appropriate direction. The problem is that for my case, the closest points on the lines are calculated to be really far away from the actual collision point. This is because the two forward lines for each object are moving away from each other as the objects pass. The problem is that because of this, no steering takes place, and the two objects partially collide. Does anyone have any suggestions as to how I can correctly calculate the point of collision? Perhaps by somehow taking into account the size of the two objects?

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• When mapping the surface of a sphere with tiles, how might you deal with polar distortion?

  - by clweeks

  It's easy to deal with the way locations interact on a clean Cartesian grid. It's just vanilla math. And you can kind of ignore the geometry of the sphere's surface for a bunch of it if you want to just truncate the poles or something. But I keep coming up with ideas for games where the polar space matters. Geo-coded ARGs and global roguelikes and stuff. I want square(ish?) locations -- reasonably representable by square tiles of the same size across the globe, anyway. This has to be a solved problem, right? What are the solutions? ETA: At the equator -- and assuming that your square locations are reasonably small, it's close enough to true that you can get away with having one square in the rows north and south of the most equatorial row. And you could probably get away with that by just hand-waving the difference up to like 45-degrees or so. But eventually, you need to have fewer squares in a pole-ward circumferential row. If I reduce the length of the row by one and offset the squares by 1/2 then they're just like hexes and it's relatively easy to do the coding to keep track of the connections. But as you get pole-ward, it gets more and more extreme. Projecting the surface of the world onto the surface of a cube is tempting. But I figured there must be more elegant solutions already in use. If I did the cube thing (not dissecting it further through geodesy) Are there any pros and cons related to placing the pole at the center of a face or at the vertex of three sides?

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• Circle-Line Collision Detection Problem

  - by jazzdawg

  I am currently developing a breakout clone and I have hit a roadblock in getting collision detection between a ball (circle) and a brick (convex polygon) working correctly. I am using a Circle-Line collision detection test where each line represents and edge on the convex polygon brick. For the majority of the time the Circle-Line test works properly and the points of collision are resolved correctly. Collision detection working correctly. However, occasionally my collision detection code returns false due to a negative discriminant when the ball is actually intersecting the brick. Collision detection failing. I am aware of the inefficiency with this method and I am using axis aligned bounding boxes to cut down on the number of bricks tested. My main concern is if there are any mathematical bugs in my code below. /* * from and to are points at the start and end of the convex polygons edge. * This function is called for every edge in the convex polygon until a * collision is detected. */ bool circleLineCollision(Vec2f from, Vec2f to) { Vec2f lFrom, lTo, lLine; Vec2f line, normal; Vec2f intersectPt1, intersectPt2; float a, b, c, disc, sqrt_disc, u, v, nn, vn; bool one = false, two = false; // set line vectors lFrom = from - ball.circle.centre; // localised lTo = to - ball.circle.centre; // localised lLine = lFrom - lTo; // localised line = from - to; // calculate a, b & c values a = lLine.dot(lLine); b = 2 * (lLine.dot(lFrom)); c = (lFrom.dot(lFrom)) - (ball.circle.radius * ball.circle.radius); // discriminant disc = (b * b) - (4 * a * c); if (disc < 0.0f) { // no intersections return false; } else if (disc == 0.0f) { // one intersection u = -b / (2 * a); intersectPt1 = from + (lLine.scale(u)); one = pointOnLine(intersectPt1, from, to); if (!one) return false; return true; } else { // two intersections sqrt_disc = sqrt(disc); u = (-b + sqrt_disc) / (2 * a); v = (-b - sqrt_disc) / (2 * a); intersectPt1 = from + (lLine.scale(u)); intersectPt2 = from + (lLine.scale(v)); one = pointOnLine(intersectPt1, from, to); two = pointOnLine(intersectPt2, from, to); if (!one && !two) return false; return true; } } bool pointOnLine(Vec2f p, Vec2f from, Vec2f to) { if (p.x >= min(from.x, to.x) && p.x <= max(from.x, to.x) && p.y >= min(from.y, to.y) && p.y <= max(from.y, to.y)) return true; return false; }

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• Change collision action

  - by PatrickR

  I have a collision detection and its working fine, the problem is, that whenever my "bird" is hitting a "cloud", the cloud dissapers and i get some points. The same happens for the "sol" which it should, but not with the clouds. How can this be changed ? ive tryed a lot, but can seem to figger it out. Collision Code - (void)update:(ccTime)dt { bird.position = ccpAdd(bird.position, skyVelocity); NSMutableArray *projectilesToDelete = [[NSMutableArray alloc] init]; for (CCSprite *bird in _projectiles) { bird.anchorPoint = ccp(0, 0); CGRect absoluteBox = CGRectMake(bird.position.x, bird.position.y, [bird boundingBox].size.width, [bird boundingBox].size.height); NSMutableArray *targetsToDelete = [[NSMutableArray alloc] init]; for (CCSprite *cloudSprite in _targets) { cloudSprite.anchorPoint = ccp(0, 0); CGRect absoluteBox = CGRectMake(cloudSprite.position.x, cloudSprite.position.y, [cloudSprite boundingBox].size.width, [cloudSprite boundingBox].size.height); if (CGRectIntersectsRect([bird boundingBox], [cloudSprite boundingBox])) { [targetsToDelete addObject:cloudSprite]; } } for (CCSprite *solSprite in _targets) { solSprite.anchorPoint = ccp(0, 0); CGRect absoluteBox = CGRectMake(solSprite.position.x, solSprite.position.y, [solSprite boundingBox].size.width, [solSprite boundingBox].size.height); if (CGRectIntersectsRect([bird boundingBox], [solSprite boundingBox])) { [targetsToDelete addObject:solSprite]; score += 50/2; [scoreLabel setString:[NSString stringWithFormat:@"%d", score]]; } } // NÅR SKYEN BLIVER RAMT AF FUGLEN for (CCSprite *cloudSprite in targetsToDelete) { //[_targets removeObject:cloudSprite]; //[self removeChild:cloudSprite cleanup:YES]; } // NÅR SOLEN BLIVER RAMT AF FUGLEN for (CCSprite *solSprite in targetsToDelete) { [_targets removeObject:solSprite]; [self removeChild:solSprite cleanup:YES]; } if (targetsToDelete.count > 0) { [projectilesToDelete addObject:bird]; } [targetsToDelete release]; } // NÅR FUGLEN BLIVER RAMT AF ALT ANDET for (CCSprite *bird in projectilesToDelete) { //[_projectiles removeObject:bird]; //[self removeChild:bird cleanup:YES]; } [projectilesToDelete release]; }

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• How to make an object move again after being stopped by collision in Unity?

  - by Matthew Underwood

  I have a player object which position is always centered on the main camera's viewport. This object has a Rigidbody 2D, a box and circle collider. The player moves around a level, the level has a polygon collider attached. I move the camera until the object hits against the collider, which stops the movement of the camera by setting its speed to 0. The problem happens when I want to move the camera / player object away from the collider. As the speed is already at 0, it cannot move away from the collider. The script attached to the player object, checks for collisions and applies the speed to 0 on the main camera's test script. using UnityEngine; using System.Collections; public class move : MonoBehaviour { public float speed; public test testing; // Use this for initialization void Start () { speed = 10F; testing = Camera.main.GetComponent<test>(); } // Update is called once per frame void FixedUpdate () { Vector3 p = Camera.main.ViewportToWorldPoint(new Vector3(0.5F, 0.5F, Camera.main.nearClipPlane)); transform.position = new Vector3(p.x, p.y, -1); } void OnCollisionEnter2D(Collision2D col) { testing.speed = 0; } void OnCollisionExit2D(Collision2D col) { testing.speed = 10F; } } This is the script attached to the main camera; just a simple script that changes the camera's position. using UnityEngine; using System.Collections; public class test : MonoBehaviour { public float speed; public float translationY; public float translationX; // Use this for initialization void Start () { speed = 10F; } void FixedUpdate () { translationY = Input.GetAxis("Vertical") * speed * Time.deltaTime; translationX = Input.GetAxis("Horizontal") * speed * Time.deltaTime; transform.Translate(translationX, translationY, 0); } } The player object isn't kinematic and is a fixed angle, the colliders aren't triggers and the polygon collider isn't a trigger either. The player is the red square, the collider is the pink area. -- EDIT -- From the latest change the collider set up for the player So if the X speed was disabled. It wouldnt move into the side of the polygon colider which is good, but yet you couldnt move away from it. And moving down would move inside the colider.

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• What would be a good filter to create 'magnetic deformers' from a depth map?

  - by sebf

  In my project, I am creating a system for deforming a highly detailed mesh (clothing) so that it 'fits' a convex mesh. To do this I use depth maps of the item and the 'hull' to determine at what point in world space the deviation occurs and the extent. Simply transforming all occluded vertices to the depths as defined by the 'hull' is fairly effective, and has good performance, but it suffers the problem of not preserving the features of the mesh and requires extensive culling to avoid false-positives. I would like instead to generate from the depth deviation map a set of simple 'deformers' which will 'push'* all vertices of the deformed mesh outwards (in world space). This way, all features of the mesh are preserved and there is no need to have complex heuristics to cull inappropriate vertices. I am not sure how to go about generating this deformer set however. I am imagining something like an algorithm that attempts to match a spherical surface to each patch of contiguous deviations within a certain range, but do not know where to start doing this. Can anyone suggest a suitable filter or algorithm for generating deformers? Or to put it another way 'compressing' a depth map? (*Push because its fitting to a convex 'bulgy' humanoid so transforms are likely to be 'spherical' from the POV of the surface.)

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• How to snap a 2D Quad to the mouse cursor using OpenGL 3.0/WIN32?

  - by NoobScratcher

  I've been having issues trying to snap a 2D Quad to the mouse cursor position I'm able : 1.) To get values into posX, posY, posZ 2.) Translate with the values from those 3 variables But the quad positioning I'm not able to do correctly in such a way that the 2D Quad is near the mouse cursor using those values from those 3 variables eg."posX, posY, posZ" I need the mouse cursor in the center of the 2D Quad. I'm hoping someone can help me achieve this. I've tried searching around with no avail. Heres the function that is ment to do the snapping but instead creates weird flicker or shows nothing at all only the 3d models show up : void display() { glClearColor(0.0,0.0,0.0,1.0); glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT); for(std::vector<GLuint>::iterator I = cube.begin(); I != cube.end(); ++I) { glCallList(*I); } if(DrawArea == true) { glReadPixels(winX, winY, 1, 1, GL_DEPTH_COMPONENT, GL_FLOAT, &winZ); cerr << winZ << endl; glGetDoublev(GL_MODELVIEW_MATRIX, modelview); glGetDoublev(GL_PROJECTION_MATRIX, projection); glGetIntegerv(GL_VIEWPORT, viewport); gluUnProject(winX, winY, winZ , modelview, projection, viewport, &posX, &posY, & posZ); glBindTexture(GL_TEXTURE_2D, DrawAreaTexture); glPixelStorei(GL_UNPACK_ALIGNMENT, 1); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST); glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_DECAL); glTexImage2D (GL_TEXTURE_2D, 0, GL_RGB, DrawAreaSurface->w, DrawAreaSurface->h, 0, GL_RGBA, GL_UNSIGNED_BYTE, DrawAreaSurface->pixels); glEnable(GL_TEXTURE_2D); glBindTexture(GL_TEXTURE_2D, DrawAreaTexture); glTranslatef(posX , posY, posZ); glBegin(GL_QUADS); glTexCoord2f (0.0, 0.0); glVertex3f(0.5, 0.5, 0); glTexCoord2f (1.0, 0.0); glVertex3f(0, 0.5, 0); glTexCoord2f (1.0, 1.0); glVertex3f(0, 0, 0); glTexCoord2f (0.0, 1.0); glVertex3f(0.5, 0, 0); glEnd(); } SwapBuffers(hDC); } I'm using : OpenGL 3.0 WIN32 API C++ GLSL if you really want the full source here it is - http://pastebin.com/1Ncm9HNf , Its pretty messy.

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