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• OpenGL 2D Depth Perception

  - by Stephen James

  This is the first time i have ever commented on a forum about programming, so sorry if I'm not specific enough. Here's my problem: I have a 2D RPG game written in Java using LWJGL. All works fine, but at the moment I'm having trouble deciding what the best way to do depth perception is. So , for example, if the player goes in front of the tree/enemy (lower than the objects y-coordinate) then show the player in front), if the player goes behind the tree/enemy (higher than the objects specific y-coordinate), then show the player behind the object. I have tried writing a block of code to deal with this, and it works quite well for the trees, but not for the enemies yet. Is there a simpler way of doing this in LWJGL that I'm missing? Thanks :)

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• Algorithm to find all tiles within a given radius on staggered isometric map

  - by kasztelan

  Given staggered isometric map and a start tile what would be the best way to get all surrounding tiles within given radius(middle to middle)? I can get all neighbours of a given tile and distance between each of them without any problems but I'm not sure what path to take after that. This feature will be used quite often (along with A*) so I'd like to avoid unecessary calculations. If it makes any difference I'm using XNA and each tile is 64x32 pixels.

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• Physics engine that can handle multiple attractors?

  - by brice

  I'm putting together a game that will be played mostly with three dimensional gravity. By that I mean multiple planets/stars/moons behaving realistically, and path plotting and path prediction in the gravity field. I have looked at a variety of physics engines, such as Bullet, tokamak or Newton, but none of them seem to be suitable, as I'd essentially have to re-write the gravity engine in their framework. Do you know of a physics engine that is capable of dealing with multiple bodies all attracted to one another? I don't need scenegraph management, or rendering, just core physics. (collision detection would be a bonus, as would rigid body dynamics). My background is in physics, so I would be able to write an engine that uses Verlet integration or RK4 (or even Euler integration, if I had to) but I'd much rather adapt an off the shelf solution. [edit]: There are some great resources for physics simulation of n-body problems online, and on stackoverflow

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• How do you stop OgreBullet Capsule from falling over?

  - by Nathan Baggs

  I've just started implementing bullet into my Ogre project. I followed the install instructions here: http://www.ogre3d.org/tikiwiki/OgreBullet+Tutorial+1 And the rest if the tutorial here: http://www.ogre3d.org/tikiwiki/OgreBullet+Tutorial+2 I got that to work fine however now I wanted to extend it to a handle a first person camera. I created a CapsuleShape and a Rigid Body (like the tutorial did for the boxes) however when I run the game the capsule falls over and rolls around on the floor, causing the camera swing wildly around. I need a way to fix the capsule to always stay upright, but I have no idea how Below is the code I'm using. (part of) Header File OgreBulletDynamics::DynamicsWorld *mWorld; // OgreBullet World OgreBulletCollisions::DebugDrawer *debugDrawer; std::deque<OgreBulletDynamics::RigidBody *> mBodies; std::deque<OgreBulletCollisions::CollisionShape *> mShapes; OgreBulletCollisions::CollisionShape *character; OgreBulletDynamics::RigidBody *characterBody; Ogre::SceneNode *charNode; Ogre::Camera* mCamera; Ogre::SceneManager* mSceneMgr; Ogre::RenderWindow* mWindow; main file bool MinimalOgre::go(void) { ... mCamera = mSceneMgr->createCamera("PlayerCam"); mCamera->setPosition(Vector3(0,0,0)); mCamera->lookAt(Vector3(0,0,300)); mCamera->setNearClipDistance(5); mCameraMan = new OgreBites::SdkCameraMan(mCamera); OgreBulletCollisions::CollisionShape *Shape; Shape = new OgreBulletCollisions::StaticPlaneCollisionShape(Vector3(0,1,0), 0); // (normal vector, distance) OgreBulletDynamics::RigidBody *defaultPlaneBody = new OgreBulletDynamics::RigidBody( "BasePlane", mWorld); defaultPlaneBody->setStaticShape(Shape, 0.1, 0.8); // (shape, restitution, friction) // push the created objects to the deques mShapes.push_back(Shape); mBodies.push_back(defaultPlaneBody); character = new OgreBulletCollisions::CapsuleCollisionShape(1.0f, 1.0f, Vector3(0, 1, 0)); charNode = mSceneMgr->getRootSceneNode()->createChildSceneNode(); charNode->attachObject(mCamera); charNode->setPosition(mCamera->getPosition()); characterBody = new OgreBulletDynamics::RigidBody("character", mWorld); characterBody->setShape( charNode, character, 0.0f, // dynamic body restitution 10.0f, // dynamic body friction 10.0f, // dynamic bodymass Vector3(0,0,0), Quaternion(0, 0, 1, 0)); mShapes.push_back(character); mBodies.push_back(characterBody); ... }

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• Thread safe double buffering

  - by kdavis8

  I am trying to implement a draw map method that will draw the tiled image across the surface of the component. I'm having issue with this code. The double buffering does not seem to be working, because the sprite flickers like crazy; my source code: package myPackage; import java.awt.Color; import java.awt.Graphics; import java.awt.Graphics2D; import java.awt.Image; import java.awt.Toolkit; import java.awt.image.BufferStrategy; import java.awt.image.BufferedImage; import javax.swing.JFrame; public class GameView extends JFrame implements Runnable { public BufferedImage backbuffer; public Graphics2D g2d; public Image img; Thread gameloop; Scene scene; public GameView() { super("Game View"); setSize(600, 600); setVisible(true); setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); backbuffer = new BufferedImage(getWidth(), getHeight(), BufferedImage.TYPE_INT_RGB); g2d = backbuffer.createGraphics(); Toolkit tk = Toolkit.getDefaultToolkit(); img = tk.getImage(this.getClass().getResource("cage.png")); scene = new Scene(g2d, this); gameloop = new Thread(this); gameloop.start(); } public static void main(String args[]) { new GameView(); } public void paint(Graphics g) { g.drawImage(backbuffer, 0, 0, this); repaint(); } @Override public void run() { // TODO Auto-generated method stub Thread t = Thread.currentThread(); while (t == gameloop) { scene.getScene("dirtmap"); g2d.drawImage(img, 80, 80,this![enter image description here][1]); } } private void drawScene(String string) { // TODO Auto-generated method stub // g2d.setColor(Color.white); // g2d.fillRect(0, 0, getWidth(), getHeight()); scene.getScene(string); } } package myPackage; import java.awt.Color; import java.awt.Component; import java.awt.Graphics; import java.awt.Graphics2D; import java.awt.Image; import java.awt.Toolkit; public class Scene { Graphics g2d; Component c; boolean loaded = false; public Scene(Graphics2D gr, Component co) { g2d = gr; c = co; } public void getScene(String mapName) { Toolkit tk = Toolkit.getDefaultToolkit(); Image tile = tk.getImage(this.getClass().getResource("dirt.png")); // g2d.setColor(Color.red); for (int y = 0; y <= 18; y++) { for (int x = 0; x <= 18; x += 1) { g2d.drawImage(tile, x * 32, y * 32, c); } } loaded = true; } }

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• "Optimal" game loop for 2D side-scroller

  - by MrDatabase

  Is it possible to describe an "optimal" (in terms of performance) layout for a 2D side-scroller's game loop? In this context the "game loop" takes user input, updates the states of game objects and draws the game objects. For example having a GameObject base class with a deep inheritance hierarchy could be good for maintenance... you can do something like the following: foreach(GameObject g in gameObjects) g.update(); However I think this approach can create performance issues. On the other hand all game objects' data and functions could be global. Which would be a maintenance headache but might be closer to an optimally performing game loop. Any thoughts? I'm interested in practical applications of near optimal game loop structure... even if I get a maintenance headache in exchange for great performance.

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• Spritesheet per pixel collision XNA

  - by Jixi

  So basically i'm using this: public bool IntersectPixels(Rectangle rectangleA, Color[] dataA,Rectangle rectangleB, Color[] dataB) { int top = Math.Max(rectangleA.Top, rectangleB.Top); int bottom = Math.Min(rectangleA.Bottom, rectangleB.Bottom); int left = Math.Max(rectangleA.Left, rectangleB.Left); int right = Math.Min(rectangleA.Right, rectangleB.Right); for (int y = top; y < bottom; y++) { for (int x = left; x < right; x++) { Color colorA = dataA[(x - rectangleA.Left) + (y - rectangleA.Top) * rectangleA.Width]; Color colorB = dataB[(x - rectangleB.Left) + (y - rectangleB.Top) * rectangleB.Width]; if (colorA.A != 0 && colorB.A != 0) { return true; } } } return false; } In order to detect collision, but i'm unable to figure out how to use it with animated sprites. This is my animation update method: public void AnimUpdate(GameTime gameTime) { if (!animPaused) { animTimer += (float)gameTime.ElapsedGameTime.TotalMilliseconds; if (animTimer > animInterval) { currentFrame++; animTimer = 0f; } if (currentFrame > endFrame || endFrame <= currentFrame || currentFrame < startFrame) { currentFrame = startFrame; } objRect = new Rectangle(currentFrame * TextureWidth, frameRow * TextureHeight, TextureWidth, TextureHeight); origin = new Vector2(objRect.Width / 2, objRect.Height / 2); } } Which works with multiple rows and columns. and how i call the intersect: public bool IntersectPixels(Obj me, Vector2 pos, Obj o) { Rectangle collisionRect = new Rectangle(me.objRect.X, me.objRect.Y, me.objRect.Width, me.objRect.Height); collisionRect.X += (int)pos.X; collisionRect.Y += (int)pos.Y; if (IntersectPixels(collisionRect, me.TextureData, o.objRect, o.TextureData)) { return true; } return false; } Now my guess is that i have to update the textureData everytime the frame changes, no? If so then i already tried it and miserably failed doing so :P Any hints, advices? If you need to see any more of my code just let me know and i'll update the question. Updated almost functional collisionRect: collisionRect = new Rectangle((int)me.Position.X, (int)me.Position.Y, me.Texture.Width / (int)((me.frameCount - 1) * me.TextureWidth), me.Texture.Height); What it does now is "move" the block up 50%, shouldn't be too hard to figure out. Update: Alright, so here's a functional collision rectangle(besides the height issue) collisionRect = new Rectangle((int)me.Position.X, (int)me.Position.Y, me.TextureWidth / (int)me.frameCount - 1, me.TextureHeight); Now the problem is that using breakpoints i found out that it's still not getting the correct color values of the animated sprite. So it detects properly but the color values are always: R:0 G:0 B:0 A:0 ??? disregard that, it's not true afterall =P For some reason now the collision area height is only 1 pixel..

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• Checkers AI Algorithm

  - by John

  I am making an AI for my checkers game and I'm trying to make it as hard as possible. Here is the current criteria for a move on the hardest difficulty: 1: Look For A Block: This is when a piece is being threatened and another piece can be moved in behind it to protect it. Here is an example: Black Moves |W| |W| |W| |W| | | |W| |W| |W| |W| |W| | | |W| |W| | | | | |W| | | | | | | | | |B| | | | | |B| | | |B| |B| |B| |B| |B| |B| | | |B| |B| |B| |B| White Blocks |W| |W| |W| |W| | | |W| | | |W| |W| |W| |W| |W| |W| | | | | |W| | | | | | | | | |B| | | | | |B| | | |B| |B| |B| |B| |B| |B| | | |B| |B| |B| |B| 2: Move pieces out of danger: if any piece is being threatened, and a piece cannot block for that piece, then it will attempt to move out of the way. If the piece cannot move out of the way without still being in danger, the computer ignores the piece. 3: If the computer player owns any kings, it will attempt to 'hunt down' enemy pieces on the board, if no moves can be made that won't in danger the king or any other pieces, the computer ignores this rule. 4: Any piece that is owned by the computer that is in column 1 or 6 will attempt to go to a side. When a piece is in column 0 or 7, it is in a very strategic position because it cannot get captured while it is in either of these columns 5: It makes an educated random move, the move will not indanger the piece that is moving or any piece that is on the board. 6: If none of the above are possible it makes a random move. This question is not really specific to any language but if all examples could be in Java that would be great, considering this app is written in android. Does anyone see any room for improvement in this algorithm? Anything that would make it better at playing checkers?

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• SlimDX and Parsing .X Files

  - by P. Avery

  I'm trying to parse a .x file using SlimDX. I can create the XFile object and register templates but I'm having problems with the enumeration object. The enumeration object has a child count of 0 for a file I know to have valid data. Here is code to create file, enumeration, and data objects: public void Parse(string filename, string templates, ref Frame aParam) { XFile xfile = null; XFileEnumerationObject enumObj = null; XFileData dataObj = null; // create file object xfile = new XFile(); // register templates if (xfile.RegisterTemplates(XFile.DefaultTemplates).IsFailure) { Console.WriteLine(Result.Last); xfile.Dispose(); return; } // create enumeration object enumObj = xfile.CreateEnumerationObject(filename, System.Runtime.InteropServices.CharSet.Auto); if (enumObj == null) { xfile.Dispose(); return; } // get child count( returns 0 here ) long ncElements = enumObj.ChildCount; for (int i = 0; i < ncElements; ++i) { // never reached... dataObj = enumObj.GetChild(i); if (dataObj.IsReference) continue; try { Parse(dataObj, ref aParam); } catch (Exception e) { e.Write(); } finally { dataObj.Dispose(); } } enumObj.Dispose(); xfile.Dispose(); } ...There are no exceptions thrown by this function...the child count is 0 so the conditional loop breaks right away, the file objects are disposed of and the function returns... Here is .x file...a simple cube: xof 0303txt 0032 Frame Root { FrameTransformMatrix { 1.000000, 0.000000, 0.000000, 0.000000, 0.000000, 1.000000, 0.000000, 0.000000, 0.000000, 0.000000, 1.000000, 0.000000, 0.000000, 0.000000, 0.000000, 1.000000;; } Frame Cube { FrameTransformMatrix { 1.000000, 0.000000, 0.000000, 0.000000, 0.000000, 1.000000, 0.000000, 0.000000, 0.000000, 0.000000, 1.000000, 0.000000, 0.000000, 0.000000, 0.000000, 1.000000;; } Mesh Cube{ //Cube Mesh 36; -1.000000; 1.000000; 1.000000;, -1.000000;-1.000000; 1.000000;, 0.999999;-1.000001; 1.000000;, -1.000000;-1.000000;-1.000000;, 1.000000;-1.000000;-1.000000;, 0.999999;-1.000001; 1.000000;, 1.000000; 0.999999; 1.000000;, -1.000000; 1.000000; 1.000000;, 0.999999;-1.000001; 1.000000;, -1.000000; 1.000000;-1.000000;, -1.000000;-1.000000;-1.000000;, -1.000000; 1.000000; 1.000000;, -1.000000; 1.000000; 1.000000;, 1.000000; 0.999999; 1.000000;, 1.000000; 1.000000;-1.000000;, 1.000000; 0.999999; 1.000000;, 0.999999;-1.000001; 1.000000;, 1.000000;-1.000000;-1.000000;, -1.000000;-1.000000;-1.000000;, -1.000000;-1.000000; 1.000000;, -1.000000; 1.000000; 1.000000;, 1.000000; 1.000000;-1.000000;, 1.000000;-1.000000;-1.000000;, -1.000000; 1.000000;-1.000000;, 1.000000; 1.000000;-1.000000;, 1.000000; 0.999999; 1.000000;, 1.000000;-1.000000;-1.000000;, -1.000000; 1.000000;-1.000000;, -1.000000; 1.000000; 1.000000;, 1.000000; 1.000000;-1.000000;, -1.000000;-1.000000; 1.000000;, -1.000000;-1.000000;-1.000000;, 0.999999;-1.000001; 1.000000;, 1.000000;-1.000000;-1.000000;, -1.000000;-1.000000;-1.000000;, -1.000000; 1.000000;-1.000000;; 12; 3;0;1;2;, 3;3;4;5;, 3;6;7;8;, 3;9;10;11;, 3;12;13;14;, 3;15;16;17;, 3;18;19;20;, 3;21;22;23;, 3;24;25;26;, 3;27;28;29;, 3;30;31;32;, 3;33;34;35;; MeshNormals { //Mesh Normals 36; 0.000000;-0.000000; 1.000000;, 0.000000;-0.000000; 1.000000;, 0.000000;-0.000000; 1.000000;, -0.000000;-1.000000;-0.000000;, -0.000000;-1.000000;-0.000000;, -0.000000;-1.000000;-0.000000;, -0.000000;-0.000000; 1.000000;, -0.000000;-0.000000; 1.000000;, -0.000000;-0.000000; 1.000000;, -1.000000; 0.000000;-0.000000;, -1.000000; 0.000000;-0.000000;, -1.000000; 0.000000;-0.000000;, 0.000000; 1.000000; 0.000000;, 0.000000; 1.000000; 0.000000;, 0.000000; 1.000000; 0.000000;, 1.000000;-0.000001; 0.000000;, 1.000000;-0.000001; 0.000000;, 1.000000;-0.000001; 0.000000;, -1.000000; 0.000000;-0.000000;, -1.000000; 0.000000;-0.000000;, -1.000000; 0.000000;-0.000000;, 0.000000; 0.000000;-1.000000;, 0.000000; 0.000000;-1.000000;, 0.000000; 0.000000;-1.000000;, 1.000000; 0.000000;-0.000000;, 1.000000; 0.000000;-0.000000;, 1.000000; 0.000000;-0.000000;, 0.000000; 1.000000; 0.000000;, 0.000000; 1.000000; 0.000000;, 0.000000; 1.000000; 0.000000;, -0.000000;-1.000000; 0.000000;, -0.000000;-1.000000; 0.000000;, -0.000000;-1.000000; 0.000000;, 0.000000;-0.000000;-1.000000;, 0.000000;-0.000000;-1.000000;, 0.000000;-0.000000;-1.000000;; 12; 3;0;1;2;, 3;3;4;5;, 3;6;7;8;, 3;9;10;11;, 3;12;13;14;, 3;15;16;17;, 3;18;19;20;, 3;21;22;23;, 3;24;25;26;, 3;27;28;29;, 3;30;31;32;, 3;33;34;35;; } //End of Mesh Normals MeshMaterialList { //Mesh Material List 1; 12; 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0;; Material Material { 0.640000; 0.640000; 0.640000; 1.000000;; 96.078431; 0.500000; 0.500000; 0.500000;; 0.000000; 0.000000; 0.000000;; TextureFilename {"Yellow.jpg";} } } //End of Mesh Material List MeshTextureCoords UVMap{ //Mesh UV Coordinates 36; 0.000000; 1.000000;, 1.000000; 1.000000;, 1.000000; 0.000000;, 0.000000; 1.000000;, 1.000000; 1.000000;, 1.000000; 0.000000;, 0.000000; 0.000000;, 0.000000; 1.000000;, 1.000000; 0.000000;, 0.000000; 1.000000;, 1.000000; 1.000000;, 0.000000; 0.000000;, 0.000000; 1.000000;, 1.000000; 1.000000;, 1.000000; 0.000000;, 0.000000; 1.000000;, 1.000000; 1.000000;, 1.000000; 0.000000;, 1.000000; 1.000000;, 1.000000; 0.000000;, 0.000000; 0.000000;, 0.000000; 0.000000;, 0.000000; 1.000000;, 1.000000; 0.000000;, 0.000000; 0.000000;, 0.000000; 1.000000;, 1.000000; 0.000000;, 0.000000; 0.000000;, 0.000000; 1.000000;, 1.000000; 0.000000;, 0.000000; 0.000000;, 0.000000; 1.000000;, 1.000000; 0.000000;, 0.000000; 1.000000;, 1.000000; 1.000000;, 1.000000; 0.000000;; } //End of Mesh UV Coordinates } //End of Mesh Mesh } //End of Cube } //End of Root Frame

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• How to fix OpenGL Co-ordinate System in SFML?

  - by Marc Alexander Reed

  My OpenGL setup is somehow configured to work like so: (-1, 1) (0, 1) (1, 1) (-1, 0) (0, 0) (1, 0) (-1, -1) (0, -1) (1, -1) How do I configure it so that it works like so: (0, 0) (SW/2, 0) (SW, 0) (0, SH/2) (SW/2, SH/2) (SW, SH/2) (0, SH) (SW/2, SH) (SW/2, SH) SW as Screen Width. SH as Screen Height. This solution would have to fix the problem of I can't translate significantly(1) on the Z axis. Depth doesn't seem to be working either. The Perspective code I'm using is that of my WORKING GLUT OpenGL code which has a cool 3d grid and camera system etc. But my OpenGL setup doesn't seem to work with SFML. Help me guys. :( Thanks in advance. :) #include <SFML/Window.hpp> #include <SFML/Graphics.hpp> #include <SFML/Audio.hpp> #include <SFML/Network.hpp> #include <SFML/OpenGL.hpp> #include "ResourcePath.hpp" //Mac-only #define _USE_MATH_DEFINES #include <cmath> double screen_width = 640.f; double screen_height = 480.f; int main (int argc, const char **argv) { sf::ContextSettings settings; settings.depthBits = 24; settings.stencilBits = 8; settings.antialiasingLevel = 2; sf::Window window(sf::VideoMode(screen_width, screen_height, 32), "SFML OpenGL", sf::Style::Close, settings); window.setActive(); glEnable(GL_DEPTH_TEST); glEnable(GL_LIGHTING); glEnable(GL_LIGHT0); glEnable(GL_NORMALIZE); glEnable(GL_COLOR_MATERIAL); glShadeModel(GL_SMOOTH); glViewport(0, 0, screen_width, screen_height); glMatrixMode(GL_PROJECTION); glLoadIdentity(); //glOrtho(0.0f, screen_width, screen_height, 0.0f, -100.0f, 100.0f); gluPerspective(45.0f, (double) screen_width / (double) screen_height , 0.f, 100.f); glClearColor(0.f, 0.f, 1.f, 0.f); //blue while (window.isOpen()) { sf::Event event; while (window.pollEvent(event)) { switch (event.type) { case sf::Event::Closed: window.close(); break; } switch (event.key.code) { case sf::Keyboard::Escape: window.close(); break; case 'W': break; case 'S': break; case 'A': break; case 'D': break; } } glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); glMatrixMode(GL_MODELVIEW); glLoadIdentity(); glTranslatef(0.f, 0.f, 0.f); glPushMatrix(); glBegin(GL_QUADS); glColor3f(1.f, 0.f, 0.f); glVertex3f(-1.f, 1.f, 0.f); glColor3f(0.f, 1.f, 0.f); glVertex3f(1.f, 1.f, 0.f); glColor3f(1.f, 0.f, 1.f); glVertex3f(1.f, -1.f, 0.f); glColor3f(0.f, 0.f, 1.f); glVertex3f(-1.f, -1.f, 0.f); glEnd(); glPopMatrix(); window.display(); } return EXIT_SUCCESS; }

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• How exactly are textures drawn on faces of cubes?

  - by Christian Frantz

  Are they drawn from the lower left corner clockwise? I know how triangles are created, I'm not just sure if textures are the same way. The texture on my cube is skewed way off and after playing around with the U,V coordinates, I still can't get it right. //front left bottom corner ok vertices[0] = (new VertexPositionTexture(new Vector3(0, 0, 0), new Vector2(1, 0))); //front left upper corner vertices[1] = (new VertexPositionTexture(new Vector3(0, 1, 0), new Vector2(1, 1))); //front right upper corner ok vertices[2] = (new VertexPositionTexture(new Vector3(1, 1, 0), new Vector2(0, 1))); //front lower right corner vertices[3] = (new VertexPositionTexture(new Vector3(1, 0, 0), new Vector2(0, 0))); //back left lower corner ok vertices[4] = (new VertexPositionTexture(new Vector3(0, 0, -1), new Vector2(0, 1))); //back left upper corner vertices[5] = (new VertexPositionTexture(new Vector3(0, 1, -1), new Vector2(1, 1))); //back right upper corner ok vertices[6] = (new VertexPositionTexture(new Vector3(1, 1, -1), new Vector2(1, 0))); //back right lower corner vertices[7] = (new VertexPositionTexture(new Vector3(1, 0, -1), new Vector2(0, 0)));

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• Best way to go about sorting 2D sprites in a "RPG Maker" styled RPG

  - by Aaron Stewart

  I am trying to come up with the best way to create overlapping sprites without having any issues. I was thinking of having a SortedDictionary and setting the Entity's key to it's Y position relative to the max bound of the simulation, aka the Z value. I'd update the "Z" value in the update method each frame, if the entity's position has changed at all. For those who don't know what I mean, I want characters who are standing closer in front of another character to be drawn on top, and if they are behind the character, they are drawn behind. I'm leery of using SpriteBatch back to front or front to back, I've been doing some searching and have been under the impression they are a bad idea. and want to know exactly how other people are dealing with their depth sorting. Just ultimately trying to come up with the best method of sorting for good practice before I get too far in to refactor the system effectively.

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• JOGL hardware based shadow mapping - computing the texture matrix

  - by axel22

  I am implementing hardware shadow mapping as described here. I've rendered the scene successfully from the light POV, and loaded the depth buffer of the scene into a texture. This texture has correctly been loaded - I check this by rendering a small thumbnail, as you can see in the screenshot below, upper left corner. The depth of the scene appears to be correct - objects further away are darker, and that are closer to the light are lighter. However, I run into trouble while rendering the scene from the camera's point of view using the depth texture - the texture on the polygons in the scene is rendered in a weird, nondeterministic fashion, as shown in the screenshot. I believe I am making an error while computing the texture transformation matrix, but I am unsure where exactly. Since I have no matrix utilities in JOGL other then the gl[Load|Mult]Matrix procedures, I multiply the matrices using them, like this: void calcTextureMatrix() { glPushMatrix(); glLoadIdentity(); glLoadMatrixf(biasmatrix, 0); glMultMatrixf(lightprojmatrix, 0); glMultMatrixf(lightviewmatrix, 0); glGetFloatv(GL_MODELVIEW_MATRIX, shadowtexmatrix, 0); glPopMatrix(); } I obtained these matrices by using the glOrtho and gluLookAt procedures: glLoadIdentity() val wdt = width / 45 val hgt = height / 45 glOrtho(wdt, -wdt, -hgt, hgt, -45.0, 45.0) glGetFloatv(GL_MODELVIEW_MATRIX, lightprojmatrix, 0) glLoadIdentity() glu.gluLookAt( xlook + lightpos._1, ylook + lightpos._2, lightpos._3, xlook, ylook, 0.0f, 0.f, 0.f, 1.0f) glGetFloatv(GL_MODELVIEW_MATRIX, lightviewmatrix, 0) My bias matrix is: float[] biasmatrix = new float[16] { 0.5f, 0.f, 0.f, 0.f, 0.f, 0.5f, 0.f, 0.f, 0.f, 0.f, 0.5f, 0.f, 0.5f, 0.5f, 0.5f, 1.f } After applying the camera projection and view matrices, I do: glTexGeni(GL_S, GL_TEXTURE_GEN_MODE, GL_EYE_LINEAR) glTexGenfv(GL_S, GL_EYE_PLANE, shadowtexmatrix, 0) glEnable(GL_TEXTURE_GEN_S) for each component. Does anybody know why the texture is not being rendered correctly? Thank you.

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• OpenGL 2D Depth Perception

  - by Stephen James

  I have a 2D RPG game written in Java using LWJGL. All works fine, but at the moment I'm having trouble deciding what the best way to do depth perception is. So , for example, if the player goes in front of the tree/enemy (lower than the objects y-coordinate) then show the player in front), if the player goes behind the tree/enemy (higher than the objects specific y-coordinate), then show the player behind the object. I have tried writing a block of code to deal with this, and it works quite well for the trees, but not for the enemies yet. Is there a simpler way of doing this in LWJGL that I'm missing?

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• Pathfinding library

  - by Shivan Dragon

  I'm an amateur game developer and somewhat amateur Java developer as well. I'm trying to find a way to have path finding for my game(s). I've first Googled for some existing Java libraries that have various path-finding implementations, but I've failed to find any. It seems to me that the only way to get pathfinding code is to use it via a game engine (like Unity). But I'd just like to have a library that I can use and make the game loop and other stuff on my own. Failing to find such a library I've tried implementing some algorithms myself. I've managed to make a running A* in Java, but for fancier stuff like D* I find it hard to do it by hand. So then, my question is, are there any Java libraries that contain at least some basic pathfinding algorithms implementations?

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• Can I use GLFW and GLEW together in the same code

  - by Brendan Webster

  I use the g++ compiler, which could be causing the main problem, but I'm using GLFW for window and input management, and I am using GLEW so that I can use OpenGL 3.x functionality. I loaded in models and then tried to make Vertex and Index buffers for the data, but it turned out that I kept getting segmentation faults in the program. I finally figured out that GLEW just wasn't working with GLFW included. Do they not work together? Also I've done the context creation through GLFW so that may be another factor in the problem.

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• Render 2 images that uses different shaders

  - by Code Vader

  Based on the giawa/nehe tutorials, how can I render 2 images with different shaders. I'm pretty new to OpenGl and shaders so I'm not completely sure whats happening in my code, but I think the shaders that is called last overwrites the first one. private static void OnRenderFrame() { // calculate how much time has elapsed since the last frame watch.Stop(); float deltaTime = (float)watch.ElapsedTicks / System.Diagnostics.Stopwatch.Frequency; watch.Restart(); // use the deltaTime to adjust the angle of the cube angle += deltaTime; // set up the OpenGL viewport and clear both the color and depth bits Gl.Viewport(0, 0, width, height); Gl.Clear(ClearBufferMask.ColorBufferBit | ClearBufferMask.DepthBufferBit); // use our shader program and bind the crate texture Gl.UseProgram(program); //<<<<<<<<<<<< TOP PYRAMID // set the transformation of the top_pyramid program["model_matrix"].SetValue(Matrix4.CreateRotationY(angle * rotate_cube)); program["enable_lighting"].SetValue(lighting); // bind the vertex positions, UV coordinates and element array Gl.BindBufferToShaderAttribute(top_pyramid, program, "vertexPosition"); Gl.BindBufferToShaderAttribute(top_pyramidNormals, program, "vertexNormal"); Gl.BindBufferToShaderAttribute(top_pyramidUV, program, "vertexUV"); Gl.BindBuffer(top_pyramidTrianlges); // draw the textured top_pyramid Gl.DrawElements(BeginMode.Triangles, top_pyramidTrianlges.Count, DrawElementsType.UnsignedInt, IntPtr.Zero); //<<<<<<<<<< CUBE // set the transformation of the cube program["model_matrix"].SetValue(Matrix4.CreateRotationY(angle * rotate_cube)); program["enable_lighting"].SetValue(lighting); // bind the vertex positions, UV coordinates and element array Gl.BindBufferToShaderAttribute(cube, program, "vertexPosition"); Gl.BindBufferToShaderAttribute(cubeNormals, program, "vertexNormal"); Gl.BindBufferToShaderAttribute(cubeUV, program, "vertexUV"); Gl.BindBuffer(cubeQuads); // draw the textured cube Gl.DrawElements(BeginMode.Quads, cubeQuads.Count, DrawElementsType.UnsignedInt, IntPtr.Zero); //<<<<<<<<<<<< BOTTOM PYRAMID // set the transformation of the bottom_pyramid program["model_matrix"].SetValue(Matrix4.CreateRotationY(angle * rotate_cube)); program["enable_lighting"].SetValue(lighting); // bind the vertex positions, UV coordinates and element array Gl.BindBufferToShaderAttribute(bottom_pyramid, program, "vertexPosition"); Gl.BindBufferToShaderAttribute(bottom_pyramidNormals, program, "vertexNormal"); Gl.BindBufferToShaderAttribute(bottom_pyramidUV, program, "vertexUV"); Gl.BindBuffer(bottom_pyramidTrianlges); // draw the textured bottom_pyramid Gl.DrawElements(BeginMode.Triangles, bottom_pyramidTrianlges.Count, DrawElementsType.UnsignedInt, IntPtr.Zero); //<<<<<<<<<<<<< STAR Gl.Disable(EnableCap.DepthTest); Gl.Enable(EnableCap.Blend); Gl.BlendFunc(BlendingFactorSrc.SrcAlpha, BlendingFactorDest.One); Gl.BindTexture(starTexture); //calculate the camera position using some fancy polar co-ordinates Vector3 position = 20 * new Vector3(Math.Cos(phi) * Math.Sin(theta), Math.Cos(theta), Math.Sin(phi) * Math.Sin(theta)); Vector3 upVector = ((theta % (Math.PI * 2)) > Math.PI) ? Vector3.Up : Vector3.Down; program_2["view_matrix"].SetValue(Matrix4.LookAt(position, Vector3.Zero, upVector)); // make sure the shader program and texture are being used Gl.UseProgram(program_2); // loop through the stars, drawing each one for (int i = 0; i < stars.Count; i++) { // set the position and color of this star program_2["model_matrix"].SetValue(Matrix4.CreateTranslation(new Vector3(stars[i].dist, 0, 0)) * Matrix4.CreateRotationZ(stars[i].angle)); program_2["color"].SetValue(stars[i].color); Gl.BindBufferToShaderAttribute(star, program_2, "vertexPosition"); Gl.BindBufferToShaderAttribute(starUV, program_2, "vertexUV"); Gl.BindBuffer(starQuads); Gl.DrawElements(BeginMode.Quads, starQuads.Count, DrawElementsType.UnsignedInt, IntPtr.Zero); // update the position of the star stars[i].angle += (float)i / stars.Count * deltaTime * 2 * rotate_stars; stars[i].dist -= 0.2f * deltaTime * rotate_stars; // if we've reached the center then move this star outwards and give it a new color if (stars[i].dist < 0f) { stars[i].dist += 5f; stars[i].color = new Vector3(generator.NextDouble(), generator.NextDouble(), generator.NextDouble()); } } Glut.glutSwapBuffers(); } The same goes for the textures, whichever one I mention last gets applied to both object?

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• Normal maps red in OpenGL?

  - by KaiserJohaan

  I am using Assimp to import 3d models, and FreeImage to parse textures. The problem I am having is that the normal maps are actually red rather than blue when I try to render them as normal diffuse textures. http://i42.tinypic.com/289ing3.png When I open the images in a image-viewing program they do indeed show up as blue. Heres when I create the texture; OpenGLTexture::OpenGLTexture(const std::vector<uint8_t>& textureData, uint32_t textureWidth, uint32_t textureHeight, TextureType textureType, Logger& logger) : mLogger(logger), mTextureID(gNextTextureID++), mTextureType(textureType) { glGenTextures(1, &mTexture); CHECK_GL_ERROR(mLogger); glBindTexture(GL_TEXTURE_2D, mTexture); CHECK_GL_ERROR(mLogger); glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, textureWidth, textureHeight, 0, glTextureFormat, GL_UNSIGNED_BYTE, &textureData[0]); CHECK_GL_ERROR(mLogger); glGenerateMipmap(GL_TEXTURE_2D); CHECK_GL_ERROR(mLogger); glBindTexture(GL_TEXTURE_2D, 0); CHECK_GL_ERROR(mLogger); } Here is my fragment shader. You can see I just commented out the normal-map parsing and treated the normal map texture as the diffuse texture to display it and illustrate the problem. As for the rest of the code it interacts as expected with the diffuse textures so I dont see a obvious problem there. "#version 330 \n \ \n \ layout(std140) uniform; \n \ \n \ const int MAX_LIGHTS = 8; \n \ \n \ struct Light \n \ { \n \ vec4 mLightColor; \n \ vec4 mLightPosition; \n \ vec4 mLightDirection; \n \ \n \ int mLightType; \n \ float mLightIntensity; \n \ float mLightRadius; \n \ float mMaxDistance; \n \ }; \n \ \n \ uniform UnifLighting \n \ { \n \ vec4 mGamma; \n \ vec3 mViewDirection; \n \ int mNumLights; \n \ \n \ Light mLights[MAX_LIGHTS]; \n \ } Lighting; \n \ \n \ uniform UnifMaterial \n \ { \n \ vec4 mDiffuseColor; \n \ vec4 mAmbientColor; \n \ vec4 mSpecularColor; \n \ vec4 mEmissiveColor; \n \ \n \ bool mHasDiffuseTexture; \n \ bool mHasNormalTexture; \n \ bool mLightingEnabled; \n \ float mSpecularShininess; \n \ } Material; \n \ \n \ uniform sampler2D unifDiffuseTexture; \n \ uniform sampler2D unifNormalTexture; \n \ \n \ in vec3 frag_position; \n \ in vec3 frag_normal; \n \ in vec2 frag_texcoord; \n \ in vec3 frag_tangent; \n \ in vec3 frag_bitangent; \n \ \n \ out vec4 finalColor; " " \n \ \n \ void CalcGaussianSpecular(in vec3 dirToLight, in vec3 normal, out float gaussianTerm) \n \ { \n \ vec3 viewDirection = normalize(Lighting.mViewDirection); \n \ vec3 halfAngle = normalize(dirToLight + viewDirection); \n \ \n \ float angleNormalHalf = acos(dot(halfAngle, normalize(normal))); \n \ float exponent = angleNormalHalf / Material.mSpecularShininess; \n \ exponent = -(exponent * exponent); \n \ \n \ gaussianTerm = exp(exponent); \n \ } \n \ \n \ vec4 CalculateLighting(in Light light, in vec4 diffuseTexture, in vec3 normal) \n \ { \n \ if (light.mLightType == 1) // point light \n \ { \n \ vec3 positionDiff = light.mLightPosition.xyz - frag_position; \n \ float dist = max(length(positionDiff) - light.mLightRadius, 0); \n \ \n \ float attenuation = 1 / ((dist/light.mLightRadius + 1) * (dist/light.mLightRadius + 1)); \n \ attenuation = max((attenuation - light.mMaxDistance) / (1 - light.mMaxDistance), 0); \n \ \n \ vec3 dirToLight = normalize(positionDiff); \n \ float angleNormal = clamp(dot(normalize(normal), dirToLight), 0, 1); \n \ \n \ float gaussianTerm = 0.0; \n \ if (angleNormal > 0.0) \n \ CalcGaussianSpecular(dirToLight, normal, gaussianTerm); \n \ \n \ return diffuseTexture * (attenuation * angleNormal * Material.mDiffuseColor * light.mLightIntensity * light.mLightColor) + \n \ (attenuation * gaussianTerm * Material.mSpecularColor * light.mLightIntensity * light.mLightColor); \n \ } \n \ else if (light.mLightType == 2) // directional light \n \ { \n \ vec3 dirToLight = normalize(light.mLightDirection.xyz); \n \ float angleNormal = clamp(dot(normalize(normal), dirToLight), 0, 1); \n \ \n \ float gaussianTerm = 0.0; \n \ if (angleNormal > 0.0) \n \ CalcGaussianSpecular(dirToLight, normal, gaussianTerm); \n \ \n \ return diffuseTexture * (angleNormal * Material.mDiffuseColor * light.mLightIntensity * light.mLightColor) + \n \ (gaussianTerm * Material.mSpecularColor * light.mLightIntensity * light.mLightColor); \n \ } \n \ else if (light.mLightType == 4) // ambient light \n \ return diffuseTexture * Material.mAmbientColor * light.mLightIntensity * light.mLightColor; \n \ else \n \ return vec4(0.0); \n \ } \n \ \n \ void main() \n \ { \n \ vec4 diffuseTexture = vec4(1.0); \n \ if (Material.mHasDiffuseTexture) \n \ diffuseTexture = texture(unifDiffuseTexture, frag_texcoord); \n \ \n \ vec3 normal = frag_normal; \n \ if (Material.mHasNormalTexture) \n \ { \n \ diffuseTexture = vec4(normalize(texture(unifNormalTexture, frag_texcoord).xyz * 2.0 - 1.0), 1.0); \n \ // vec3 normalTangentSpace = normalize(texture(unifNormalTexture, frag_texcoord).xyz * 2.0 - 1.0); \n \ //mat3 tangentToWorldSpace = mat3(normalize(frag_tangent), normalize(frag_bitangent), normalize(frag_normal)); \n \ \n \ // normal = tangentToWorldSpace * normalTangentSpace; \n \ } \n \ \n \ if (Material.mLightingEnabled) \n \ { \n \ vec4 accumLighting = vec4(0.0); \n \ \n \ for (int lightIndex = 0; lightIndex < Lighting.mNumLights; lightIndex++) \n \ accumLighting += Material.mEmissiveColor * diffuseTexture + \n \ CalculateLighting(Lighting.mLights[lightIndex], diffuseTexture, normal); \n \ \n \ finalColor = pow(accumLighting, Lighting.mGamma); \n \ } \n \ else { \n \ finalColor = pow(diffuseTexture, Lighting.mGamma); \n \ } \n \ } \n"; Why is this? does normal-map textures need some sort of special treatment in opengl?

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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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• Adding Vertices to a dynamic mesh via Method Call

  - by Raven Dreamer

  I have a C# Struct with a static method, "Get Shape" which populates a List with the vertices of a polyhedron. Method Signature: public static void GetShape(Block b, int x, int y, int z, List<Vector3> vertices, List<int> triangles, List<Vector2> uvs, List<Vector2> uv2s) Adding directly to the vertices list (via vertices.Add(vector3) ), the code works as expected, and the new polyhedron appears when I trigger the method. However, I want to do some processing on the vertices I'm adding (a rotation), and the most sensible way I can think to do that is by creating a separate list of Vector3s, and then combining the lists when I'm done. However, vertices.AddRange(newVerts) does not add the shape to the mesh, nor does a foreach loop with verts.Add(vertices[i]). And this is before I've added in any of the processing! I have a feeling this might stem from passing the list of vertices in as a parameter, rather than returning a list and then adding to the vertices in the calling object, but since I'm filling 4 lists, I was trying to avoid having to create a data struct to return all four at once. Any ideas? The working version of the method is reprinted below, in full: public static void GetShape(Block b, int x, int y, int z, List<Vector3> vertices, List<int> triangles, List<Vector2> uvs, List<Vector2> uv2s) { //List<Vector3> vertices = new List<Vector3>(); int l_blockShape = b.blockShape; int l_blockType = b.blockType; //CheckFace checks if the block is empty //if this block is empty, don't draw anything. int vertexIndex; //only y faces need to be hidden. //if((l_blockShape & BlockShape.NegZFace) == BlockShape.NegZFace) { vertexIndex = vertices.Count; //top left, top right, bottom right, bottom left vertices.Add(new Vector3(x+.2f, y + 1, z+.2f)); vertices.Add(new Vector3(x+.8f, y + 1, z+.2f)); vertices.Add(new Vector3(x+.8f, y , z+.2f)); vertices.Add(new Vector3(x+.2f, y , z+.2f)); // first triangle for the face triangles.Add(vertexIndex); triangles.Add(vertexIndex+1); triangles.Add(vertexIndex+3); // second triangle for the face triangles.Add(vertexIndex+1); triangles.Add(vertexIndex+2); triangles.Add(vertexIndex+3); //UVs for the face uvs.Add( new Vector2(0,1)); uvs.Add( new Vector2(1,1)); uvs.Add( new Vector2(1,0)); uvs.Add( new Vector2(0,0)); //UV2s (lightmapping?) uv2s.Add( new Vector2(0,1)); uv2s.Add( new Vector2(1,1)); uv2s.Add( new Vector2(1,0)); uv2s.Add( new Vector2(0,0)); } //XY Z+1 face //if((l_blockShape & BlockShape.PosZFace) == BlockShape.PosZFace) { vertexIndex = vertices.Count; //top left, top right, bottom right, bottom left vertices.Add(new Vector3(x+.8f, y + 1, z+.8f)); vertices.Add(new Vector3(x+.2f, y + 1, z+.8f)); vertices.Add(new Vector3(x+.2f, y , z+.8f)); vertices.Add(new Vector3(x+.8f, y , z+.8f)); // first triangle for the face triangles.Add(vertexIndex); triangles.Add(vertexIndex+1); triangles.Add(vertexIndex+3); // second triangle for the face triangles.Add(vertexIndex+1); triangles.Add(vertexIndex+2); triangles.Add(vertexIndex+3); //UVs for the face uvs.Add( new Vector2(0,1)); uvs.Add( new Vector2(1,1)); uvs.Add( new Vector2(1,0)); uvs.Add( new Vector2(0,0)); //UV2s (lightmapping?) uv2s.Add( new Vector2(0,1)); uv2s.Add( new Vector2(1,1)); uv2s.Add( new Vector2(1,0)); uv2s.Add( new Vector2(0,0)); } //ZY face //if((l_blockShape & BlockShape.NegXFace) == BlockShape.NegXFace) { vertexIndex = vertices.Count; //top left, top right, bottom right, bottom left vertices.Add(new Vector3(x+.2f, y + 1, z+.8f)); vertices.Add(new Vector3(x+.2f, y + 1, z+.2f)); vertices.Add(new Vector3(x+.2f, y , z+.2f)); vertices.Add(new Vector3(x+.2f, y , z+.8f)); // first triangle for the face triangles.Add(vertexIndex); triangles.Add(vertexIndex+1); triangles.Add(vertexIndex+3); // second triangle for the face triangles.Add(vertexIndex+1); triangles.Add(vertexIndex+2); triangles.Add(vertexIndex+3); //UVs for the face uvs.Add( new Vector2(0,1)); uvs.Add( new Vector2(1,1)); uvs.Add( new Vector2(1,0)); uvs.Add( new Vector2(0,0)); //UV2s (lightmapping?) uv2s.Add( new Vector2(0,1)); uv2s.Add( new Vector2(1,1)); uv2s.Add( new Vector2(1,0)); uv2s.Add( new Vector2(0,0)); } //ZY X+1 face // if((l_blockShape & BlockShape.PosXFace) == BlockShape.PosXFace) { vertexIndex = vertices.Count; //top left, top right, bottom right, bottom left vertices.Add(new Vector3(x+.8f, y + 1, z+.2f)); vertices.Add(new Vector3(x+.8f, y + 1, z+.8f)); vertices.Add(new Vector3(x+.8f, y , z+.8f)); vertices.Add(new Vector3(x+.8f, y , z+.2f)); // first triangle for the face triangles.Add(vertexIndex); triangles.Add(vertexIndex+1); triangles.Add(vertexIndex+3); // second triangle for the face triangles.Add(vertexIndex+1); triangles.Add(vertexIndex+2); triangles.Add(vertexIndex+3); //UVs for the face uvs.Add( new Vector2(0,1)); uvs.Add( new Vector2(1,1)); uvs.Add( new Vector2(1,0)); uvs.Add( new Vector2(0,0)); //UV2s (lightmapping?) uv2s.Add( new Vector2(0,1)); uv2s.Add( new Vector2(1,1)); uv2s.Add( new Vector2(1,0)); uv2s.Add( new Vector2(0,0)); } //ZX face if((l_blockShape & BlockShape.NegYFace) == BlockShape.NegYFace) { vertexIndex = vertices.Count; //top left, top right, bottom right, bottom left vertices.Add(new Vector3(x+.8f, y , z+.8f)); vertices.Add(new Vector3(x+.8f, y , z+.2f)); vertices.Add(new Vector3(x+.2f, y , z+.2f)); vertices.Add(new Vector3(x+.2f, y , z+.8f)); // first triangle for the face triangles.Add(vertexIndex+3); triangles.Add(vertexIndex+1); triangles.Add(vertexIndex); // second triangle for the face triangles.Add(vertexIndex+3); triangles.Add(vertexIndex+2); triangles.Add(vertexIndex+1); //UVs for the face uvs.Add( new Vector2(0,1)); uvs.Add( new Vector2(1,1)); uvs.Add( new Vector2(1,0)); uvs.Add( new Vector2(0,0)); //UV2s (lightmapping?) uv2s.Add( new Vector2(0,1)); uv2s.Add( new Vector2(1,1)); uv2s.Add( new Vector2(1,0)); uv2s.Add( new Vector2(0,0)); } //ZX + 1 face if((l_blockShape & BlockShape.PosYFace) == BlockShape.PosYFace) { vertexIndex = vertices.Count; //top left, top right, bottom right, bottom left vertices.Add(new Vector3(x+.8f, y+1 , z+.2f)); vertices.Add(new Vector3(x+.8f, y+1 , z+.8f)); vertices.Add(new Vector3(x+.2f, y+1 , z+.8f)); vertices.Add(new Vector3(x+.2f, y+1 , z+.2f)); // first triangle for the face triangles.Add(vertexIndex+3); triangles.Add(vertexIndex+1); triangles.Add(vertexIndex); // second triangle for the face triangles.Add(vertexIndex+3); triangles.Add(vertexIndex+2); triangles.Add(vertexIndex+1); //UVs for the face uvs.Add( new Vector2(0,1)); uvs.Add( new Vector2(1,1)); uvs.Add( new Vector2(1,0)); uvs.Add( new Vector2(0,0)); //UV2s (lightmapping?) uv2s.Add( new Vector2(0,1)); uv2s.Add( new Vector2(1,1)); uv2s.Add( new Vector2(1,0)); uv2s.Add( new Vector2(0,0)); } }

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• Sliding collision response

  - by dbostream

  I have been reading plenty of tutorials about sliding collision responses yet I am not able to implement it properly in my project. What I want to do is make a puck slide along the rounded corner boards of a hockey rink. In my latest attempt the puck does slide along the boards but there are some strange velocity behaviors. First of all the puck slows down a lot pretty much right away and then it slides for awhile and stops before exiting the corner. Even if I double the speed I get a similar behavior and the puck does not make it out of the corner. I used some ideas from this document http://www.peroxide.dk/papers/collision/collision.pdf. This is what I have: Update method called from the game loop when it is time to update the puck (I removed some irrelevant parts). I use two states (current, previous) which are used to interpolate the position during rendering. public override void Update(double fixedTimeStep) { /* Acceleration is set to 0 for now. */ Acceleration.Zero(); PreviousState = CurrentState; _collisionRecursionDepth = 0; CurrentState.Position = SlidingCollision(CurrentState.Position, CurrentState.Velocity * fixedTimeStep + 0.5 * Acceleration * fixedTimeStep * fixedTimeStep); /* Should not this be affected by a sliding collision? and not only the position. */ CurrentState.Velocity = CurrentState.Velocity + Acceleration * fixedTimeStep; Heading = Vector2.NormalizeRet(CurrentState.Velocity); } private Vector2 SlidingCollision(Vector2 position, Vector2 velocity) { if(_collisionRecursionDepth > 5) return position; bool collisionFound = false; Vector2 futurePosition = position + velocity; Vector2 intersectionPoint = new Vector2(); Vector2 intersectionPointNormal = new Vector2(); /* I did not include the collision detection code, if a collision is detected the intersection point and normal in that point is returned. */ if(!collisionFound) return futurePosition; /* If no collision was detected it is safe to move to the future position. */ /* It is not exactly the intersection point, but slightly before. */ Vector2 newPosition = intersectionPoint; /* oldVelocity is set to the distance from the newPosition(intersection point) to the position it had moved to had it not collided. */ Vector2 oldVelocity = futurePosition - newPosition; /* Project the distance left to move along the intersection normal. */ Vector2 newVelocity = oldVelocity - intersectionPointNormal * oldVelocity.DotProduct(intersectionPointNormal); if(newVelocity.LengthSq() < 0.001) return newPosition; /* If almost no speed, no need to continue. */ _collisionRecursionDepth++; return SlidingCollision(newPosition, newVelocity); } What am I doing wrong with the velocity? I have been staring at this for very long so I have gone blind. I have tried different values of recursion depth but it does not seem to make it better. Let me know if you need more information. I appreciate any help. EDIT: A combination of Patrick Hughes' and teodron's answers solved the velocity problem (I think), thanks a lot! This is the new code: I decided to use a separate recursion method now too since I don't want to recalculate the acceleration in each recursion. public override void Update(double fixedTimeStep) { Acceleration.Zero();// = CalculateAcceleration(fixedTimeStep); PreviousState = new MovingEntityState(CurrentState.Position, CurrentState.Velocity); CurrentState = SlidingCollision(CurrentState, fixedTimeStep); Heading = Vector2.NormalizeRet(CurrentState.Velocity); } private MovingEntityState SlidingCollision(MovingEntityState state, double timeStep) { bool collisionFound = false; /* Calculate the next position given no detected collision. */ Vector2 futurePosition = state.Position + state.Velocity * timeStep; Vector2 intersectionPoint = new Vector2(); Vector2 intersectionPointNormal = new Vector2(); /* I did not include the collision detection code, if a collision is detected the intersection point and normal in that point is returned. */ /* If no collision was detected it is safe to move to the future position. */ if (!collisionFound) return new MovingEntityState(futurePosition, state.Velocity); /* Set new position to the intersection point (slightly before). */ Vector2 newPosition = intersectionPoint; /* Project the new velocity along the intersection normal. */ Vector2 newVelocity = state.Velocity - 1.90 * intersectionPointNormal * state.Velocity.DotProduct(intersectionPointNormal); /* Calculate the time of collision. */ double timeOfCollision = Math.Sqrt((newPosition - state.Position).LengthSq() / (futurePosition - state.Position).LengthSq()); /* Calculate new time step, remaining time of full step after the collision * current time step. */ double newTimeStep = timeStep * (1 - timeOfCollision); return SlidingCollision(new MovingEntityState(newPosition, newVelocity), newTimeStep); } Even though the code above seems to slide the puck correctly please have a look at it. I have a few questions, if I don't multiply by 1.90 in the newVelocity calculation it doesn't work (I get a stack overflow when the puck enters the corner because the timeStep decreases very slowly - a collision is found early in every recursion), why is that? what does 1.90 really do and why 1.90? Also I have a new problem, the puck does not move parallell to the short side after exiting the curve; to be more exact it moves outside the rink (I am not checking for any collisions with the short side at the moment). When I perform the collision detection I first check that the puck is in the correct quadrant. For example bottom-right corner is quadrant four i.e. circleCenter.X < puck.X && circleCenter.Y puck.Y is this a problem? or should the short side of the rink be the one to make the puck go parallell to it and not the last collision in the corner? EDIT2: This is the code I use for collision detection, maybe it has something to do with the fact that I can't make the puck slide (-1.0) but only reflect (-2.0): /* Point is the current position (not the predicted one) and quadrant is 4 for the bottom-right corner for example. */ if (GeometryHelper.PointInCircleQuadrant(circleCenter, circleRadius, state.Position, quadrant)) { /* The line is: from = state.Position, to = futurePosition. So a collision is detected when from is inside the circle and to is outside. */ if (GeometryHelper.LineCircleIntersection2d(state.Position, futurePosition, circleCenter, circleRadius, intersectionPoint, quadrant)) { collisionFound = true; /* Set the intersection point to slightly before the real intersection point (I read somewhere this was good to do because of floting point precision, not sure exactly how much though). */ intersectionPoint = intersectionPoint - Vector2.NormalizeRet(state.Velocity) * 0.001; /* Normal at the intersection point. */ intersectionPointNormal = Vector2.NormalizeRet(circleCenter - intersectionPoint) } } When I set the intersection point, if I for example use 0.1 instead of 0.001 the puck travels further before it gets stuck, but for all values I have tried (including 0 - the real intersection point) it gets stuck somewhere (but I necessarily not get a stack overflow). Can something in this part be the cause of my problem? I can see why I get the stack overflow when using -1.0 when calculating the new velocity vector; but not how to solve it. I traced the time steps used in the recursion (initial time step is always 1/60 ~ 0.01666): Recursion depth Time step next recursive call [Start recursion, time step ~ 0.016666] 0 0,000985806527246773 [No collision, stop recursion] [Start recursion, time step ~ 0.016666] 0 0,0149596704364629 1 0,0144883449376379 2 0,0143155612984837 3 0,014224925727213 4 0,0141673917461608 5 0,0141265435314026 6 0,0140953966184117 7 0,0140704653746625 ...and so on. As you can see the collision is detected early in every recursive call which means the next time step decreases very slowly thus the recursion depth gets very big - stack overflow.

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• Converting 3 axis vectors to a rotation matrix

  - by user38858

  I am trying to get a rotation matrix (in 3dsmax) from 3 vectors that form an axis (all 3 vectors are aligned by 90 degrees each other) Somewhere I read that I could build a rotation matrix just by inserting in every row one vector at a time (source: http://renderdan.blogspot.cz/2006/05/rotation-matrix-from-axis-vectors.html) So, I built a matrix with these example vectors x-axis : [-0.194624,-0.23715,-0.951778] y-axis : [-0.773012,0.634392,0] z-axis : [-0.6038,-0.735735,0.306788] But for some reason, if I try to convert this matrix to eulerangles, I receive this rotation: (eulerAngles 47.7284 6.12831 36.8263) ... which is totally wrong, and doesn't align to my 3 vectors at all. I know that rotation is quite difficult to understand, may someone shed some light? :)

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• Textures do not render on ATI graphics cards?

  - by Mathias Lykkegaard Lorenzen

  I'm rendering textured quads to an orthographic view in XNA through hardware instancing. On Nvidia graphics cards, this all works, tested on 3 machines. On ATI cards, it doesn't work at all, tested on 2 machines. How come? Culling perhaps? My orthographic view is set up like this: Matrix projection = Matrix.CreateOrthographicOffCenter(0, graphicsDevice.Viewport.Width, -graphicsDevice.Viewport.Height, 0, 0, 1); And my elements are rendered with the Z-coordinate 0. Edit: I just figured out something weird. If I do not call this spritebatch code above doing my textured quad rendering code, then it won't work on Nvidia cards either. Could that be due to culling information or something like that? Batch.Instance.SpriteBatch.Begin(SpriteSortMode.Immediate, BlendState.AlphaBlend, SamplerState.LinearClamp, DepthStencilState.Default, RasterizerState.CullNone); ... spriteBatch.End(); Edit 2: Here's the full code for my instancing call. public void DrawTextures() { Batch.Instance.SpriteBatch.Begin(SpriteSortMode.Texture, BlendState.AlphaBlend, SamplerState.LinearClamp, DepthStencilState.Default, RasterizerState.CullNone, textureEffect); while (texturesToDraw.Count > 0) { TextureJob texture = texturesToDraw.Dequeue(); spriteBatch.Draw(texture.Texture, texture.DestinationRectangle, texture.TintingColor); } spriteBatch.End(); #if !NOTEXTUREINSTANCING // no work to do if (positionInBufferTextured > 0) { device.BlendState = BlendState.Opaque; textureEffect.CurrentTechnique = textureEffect.Techniques["Technique1"]; textureEffect.Parameters["Texture"].SetValue(darkTexture); textureEffect.CurrentTechnique.Passes[0].Apply(); if ((textureInstanceBuffer == null) || (positionInBufferTextured > textureInstanceBuffer.VertexCount)) { if (textureInstanceBuffer != null) textureInstanceBuffer.Dispose(); textureInstanceBuffer = new DynamicVertexBuffer(device, texturedInstanceVertexDeclaration, positionInBufferTextured, BufferUsage.WriteOnly); } if (positionInBufferTextured > 0) { textureInstanceBuffer.SetData(texturedInstances, 0, positionInBufferTextured, SetDataOptions.Discard); } device.Indices = textureIndexBuffer; device.SetVertexBuffers(textureGeometryBuffer, new VertexBufferBinding(textureInstanceBuffer, 0, 1)); device.DrawInstancedPrimitives(PrimitiveType.TriangleStrip, 0, 0, textureGeometryBuffer.VertexCount, 0, 2, positionInBufferTextured); // now that we've drawn, it's ok to reset positionInBuffer back to zero, // and write over any vertices that may have been set previously. positionInBufferTextured = 0; } #endif }

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• How can I make a game like doodlejump XNA c#

  - by Ramy

  I wanted to know how can I make the background scroll down like doodlejump. I have a game made and I have to transform it so it's like doodle jump, but I'm wonder how or where to look so I can make he background keep moving as in progressing through the background till let's say the character dies. namespace IFM20884 { using System; using System.Collections.Generic; using System.Linq; using System.Text; using Microsoft.Xna.Framework; using Microsoft.Xna.Framework.Content; using Microsoft.Xna.Framework.Graphics; public abstract class BackgroundScroll : Sprite { private float speedOfBackground = 0.2f; // speed that the background moves public BackgroundScroll (GraphicsDeviceManager graphics) : base(graphics.GraphicsDevice.Viewport.Width / 2f, graphics.GraphicsDevice.Viewport.Height / 2f) { } //Getter public float speedOfBackground { get { return this.speedOfBackground ; } set { this.speedOfBackground = value; } } public override void Update(GameTime gameTime, GraphicsDeviceManager graphics) { //Makes background go down. ForcePosition(Position.X, Position.Y + (gameTime.ElapsedGameTime.Milliseconds * this.speedOfBackground )); if (Position.Y - (Height / 2) > graphics.GraphicsDevice.Viewport.Height) { ForcePosition(Position.X, Position.Y - this.Height); } } public override void Draw(SpriteBatch spriteBatch) { ForcePosition(Position.X, Position.Y - this.Height); base.Draw(spriteBatch); ForcerPosition(Position.X, Position.Y + this.Height); base.Draw(spriteBatch); } } }

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• Geometry Shader: distortions

  - by Christophe Lionet

  This is a cross-question from Stack Overflow, I thought it would be more appropriate here. There is a lot of code I could be posting. To avoid overloading the page with code, I will post any part of the code if requested. I am working from the ParticleGS DirectX10 sample, to build a geometry shader based particle system in DirectX 11. Using the sample code, and changing it to my liking, I am able to draw a single quad (which is essentially one particle constantly recreating itself). However, I noticed a problem which was similar to one I once had: the rendered shape is distorted. Here is a video showcasing what is happening. http://youtu.be/6NY_hxjMfwY Now, I used to have this issue when using several effects together, when I realised that I needed to explicitely set the geometry shader to null for the other effects. I solved this problem, as you can see in the video, as the rest of the scene is drawing properly. Note that some sides are being culled somehow, although I turned off culling in my main render state. The texturing is fine too, the texture draws with appropriate proportions relative to the quad. I really don't see what I could be doing wrong here... what would cause the geometry shader to behave in such a way? Again, I will post any piece code you will request.

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