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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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• Why do I get this file loading exception when trying to draw sprites with libgdx?

  - by BluFire

  I'm having trouble with the "Drawing Images" section on the libgdx tutorial. I set up the documents completely and I typed the code as follows: public class Game implements ApplicationListener { public static final String LOG = Game.class.getSimpleName(); private FPSLogger fpsLogger; private SpriteBatch batch; private Texture texture; private Sprite sprite; private TextureRegion region; //removed irrelevant code for this question... @Override public void render() { texture = new Texture(Gdx.files.internal("android.png")); region = new TextureRegion(texture, 20, 20, 50, 50); sprite = new Sprite(texture, 20, 20, 50, 50); sprite.setPosition(10, 10); sprite.setRotation(45); Gdx.gl.glClearColor(0f, 1f, 0f, 1f); Gdx.gl.glClear(GL20.GL_COLOR_BUFFER_BIT); batch.begin(); batch.draw(texture,10,10); batch.draw(region,10,10); sprite.draw(batch); batch.end(); // output the current FPS fpsLogger.log(); } } I went through the tutorial on the website but when I run the code I get errors: Exception in thread "LWJGL Application" com.badlogic.gdx.utils.GdxRuntimeException: Couldn't load file: android.png at com.badlogic.gdx.graphics.Pixmap.<init>(Pixmap.java:137) at com.badlogic.gdx.graphics.glutils.FileTextureData.prepare(FileTextureData.java:55) at com.badlogic.gdx.graphics.Texture.load(Texture.java:175) at com.badlogic.gdx.graphics.Texture.create(Texture.java:159) at com.badlogic.gdx.graphics.Texture.<init>(Texture.java:133) at com.badlogic.gdx.graphics.Texture.<init>(Texture.java:122) at com.game.Game.render(Game.java:46) at com.badlogic.gdx.backends.lwjgl.LwjglApplication.mainLoop (LwjglApplication.java:163) at com.badlogic.gdx.backends.lwjgl.LwjglApplication$1.run(LwjglApplication.java:113) Caused by: com.badlogic.gdx.utils.GdxRuntimeException: File not found: android.png (Internal) at com.badlogic.gdx.files.FileHandle.read(FileHandle.java:108) at com.badlogic.gdx.files.FileHandle.length(FileHandle.java:364) at com.badlogic.gdx.files.FileHandle.readBytes(FileHandle.java:156) at com.badlogic.gdx.graphics.Pixmap.<init>(Pixmap.java:134) ... 8 more I set the android.png in my assests folder in my android project linking it to the desktop one, I don't understand what I'm doing wrong. What is making these errors? FIX. Weird ending.this was the plus where the sprite is suppose to look like. The top right corner of the next image should look like, the bottom left is what turned out in the code. I'm think it was because of the texture region but I'm not 100%. Can somebody explain why it is really warped? I thought the changes I made in the coding will just change position/rotation, rather then a change in the image.

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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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• 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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• 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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• 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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• XNA 2D line-of-sight check

  - by bionicOnion

  I'm working on a top-down shooter in XNA, and I need to implement line-of-sight checking. I've come up with a solution that seems to work, but I get the nagging feeling that it won't be efficient enough to do every frame for multiple calls (the game already hiccups slightly at about 10 calls per frame). The code is below, but my general plan was to create a series of rectangles with a width and height of zero to act as points along the sight line, and then check to see if any of these rectangles intersects a ClutterObject (an interface I defined for things like walls or other obstacles) after first screening for any that can't possibly be in the line of sight (i.e. behind the viewer) or are too far away (a concession I made for efficiency). public static bool LOSCheck(Vector2 pos1, Vector2 pos2) { Vector2 currentPos = pos1; Vector2 perMove = (pos2 - pos1); perMove.Normalize(); HashSet<ClutterObject> clutter = new HashSet<ClutterObject>(); foreach (Room r in map.GetRooms()) { if (r != null) { foreach (ClutterObject c in r.GetClutter()) { if (c != null &&!(c.GetRectangle().X * perMove.X < 0) && !(c.GetRectangle().Y * perMove.Y < 0)) { Vector2 cVector = new Vector2(c.GetRectangle().X, c.GetRectangle().Y); if ((cVector - pos1).Length() < 1500) clutter.Add(c); } } } } while (currentPos != pos2 && ((currentPos - pos1).Length() < 1500)) { Rectangle position = new Rectangle((int)currentPos.X, (int)currentPos.Y, 0, 0); foreach (ClutterObject c in clutter) { if (position.Intersects(c.GetRectangle())) return false; } currentPos += perMove; } return true; } I'm sure that there's a better way to do this (or at least a way to make this method more efficient), but I'm not too used to XNA yet, so I figured it couldn't hurt to bring it here. At the very least, is there an efficient to determine which objects may be in front of the viewer with greater precision than the rather broad 90 degree window I've given myself?

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• glm quaternion camera rotating on wrong axis

  - by Jarrett

  I'm trying to get my camera implemented with a glm::quat used to store the rotation. However, whenever I do circles with the mouse, the camera rotates along the axis I am viewing (i.e. I think it's called the target axis). For example, if I rotated the mouse in a clockwise fashion, the camera rotates clockwise around the axis. I initialize my quaternion like so: void Camera::initialize() { orientationQuaternion_ = glm::quat(); orientationQuaternion_ = glm::normalize(orientationQuaternion_); } I rotate like so: void Camera::rotate(const glm::detail::float32& degrees, const glm::vec3& axis) { orientationQuaternion_ = orientationQuaternion_ * glm::normalize(glm::angleAxis(degrees, axis)); } and I set the viewMatrix like so: void Camera::render() { glm::quat temp = glm::conjugate(orientationQuaternion_); viewMatrix_ = glm::mat4_cast(temp); viewMatrix_ = glm::translate(viewMatrix_, glm::vec3(-pos_.x, -pos_.y, -pos_.z)); } The only axis' I actually try to rotate are the X and Y axis (i.e. (1,0,0) and (0,1,0)). Anyone have any idea why I see my camera rotating around the target axis?

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• Where can I buy freely redistributable (creative commons) game assets?

  - by Erlend

  I'd like to know about any 3D asset shops out there that specialize in game assets and, most importantly, license their assets under an open license like Creative Commons or similarly permissive. We are looking to buy some professional looking assets for use and redistribution with our open source 3D game engine. The problem is that all the commercial 3D assets we've come by are only sold under very restrictive licenses, which won't allow us to include the models in our code repository (since free code hosting repositories require that all your data, including media, is open source or otherwise copyleft) nor in turn redistribute the assets as part of our downloadable SDK. I realize this sounds like a weak business idea, since users could just buy the asset and start sharing it with everyone. But somehow this has worked for hundreds of WordPress theme shops, so I was hoping maybe someone's trying similar things for commercial game assets.

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• Blender to Collada to Assimp - Rigid (Non-skinned) Animation

  - by gareththegeek

  I am trying to get simple animations to work, exporting from Blender and importing into my application. My first attempt was as follows: Open Blender at factory settings. Select the default cube and insert a location keyframe. Select another frame and move the cube. Insert a second location keyframe. Export to Collada. When I open the Collada file using assimp it contains zero animations, even though in Blender the cube animates correctly. On my next attempt, I inserted a bone armature with a single bone, made it the parent of the cube, and animated the bone instead. Again the animation worked correctly in Blender. Assimp now lists one animation but both key frames have the position [0, 0, 0] Does anyone have any suggestions as to how I can get animated (non-skinned) meshes from Blender into Assimp? My ultimate goal here is to export animated meshes from Blender, process them offline into my own model format, and load them into my SharpDX based graphics engine..

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• Using model tools as map editor

  - by cooky451

  I want to make a game which would require a 3D map editor. Of course, I would like to avoid creating such an editor. My idea is now to use modeling tools (3DS Max, Maya, Blender) to create the map, and to give game specific objects specified names. This way I'd just need to write an COLLADA - native map format converter. But I'm not sure if this is possible the way I imagine it, that's why I'd like to hear your thoughts on the matter. Are modeling tools suitable to create big open world maps? Can this "naming convention"-idea for game specific objects work? Are the modeling tools able to export a scene in chunks / in a way that occlusion culling and collision detection can be properly done? If not: Is there a way to build a suitable data structure from the exported data?

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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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• Camera wont stay behind model after pitch, then rotation

  - by ChocoMan

  I have a camera position behind a model. Currently, if I push the left thumbstick making my model move forward, backward, or strafe, the camera stays with the model. If I push the right thumbstick left or right, the model rotates in those directions fine along with the camera rotating while maintaining its position relatively behind the model. But when I pitch the model up or down, then rotate the model afterwards, the camera moves slightly rotates in a clock-like fashion behind the model. If I do a few rotations of the model and try to pitch the camera, the camera will eventually be looking at the side, then eventually the front of the model while also rotating in a clock-like fashion. My question is, how do I keep the camera to pitch up and down behind the model no matter how much the model has rotated? Here is what I got: // Rotates model and pitches camera on its own axis public void modelRotMovement(GamePadState pController) { // Rotates Camera with model Yaw = pController.ThumbSticks.Right.X * MathHelper.ToRadians(angularSpeed); // Pitches Camera around model Pitch = pController.ThumbSticks.Right.Y * MathHelper.ToRadians(angularSpeed); AddRotation = Quaternion.CreateFromYawPitchRoll(Yaw, 0, 0); ModelLoad.MRotation *= AddRotation; MOrientation = Matrix.CreateFromQuaternion(ModelLoad.MRotation); } // Orbit (yaw) Camera around with model (only seeing back of model) public void cameraYaw(Vector3 axisYaw, float yaw) { ModelLoad.CameraPos = Vector3.Transform(ModelLoad.CameraPos - ModelLoad.camTarget, Matrix.CreateFromAxisAngle(axisYaw, yaw)) + ModelLoad.camTarget; } // Raise camera above or below model's shoulders public void cameraPitch(Vector3 axisPitch, float pitch) { ModelLoad.CameraPos = Vector3.Transform(ModelLoad.CameraPos - ModelLoad.camTarget, Matrix.CreateFromAxisAngle(axisPitch, pitch)) + ModelLoad.camTarget; } // Call in update method public void updateCamera() { cameraYaw(Vector3.Up, Yaw); cameraPitch(Vector3.Right, Pitch); } NOTE: I tried to use addPitch just like addRotation but it didn't work...

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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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• Detect two specific objects collision with bullet physics

  - by sebap123

  I have got some problem with defining collision between objects in my game using bullet physics. I know that objects are colliding with each other simultaneously and I don't have to do anything more. However I need to be noticed when one object collides with one of the rest. It is quite awkward written so I will tell what I want to achive. I have got ball which hits wall from tubes. Everything is on the floor. When ball hits wall some fragments fall down to infinity. So I have got bellow floor btStaticPlaneShape. This is place where most of objects is stoping and then I can start another action. But not all of them. So I've been trying to use function checkCollideWith but it isn't good method as it was said in reference and wiki. So I've checked method described in wiki http://bulletphysics.org/mediawiki-1.5.8/index.php/Collision_Callbacks_and_Triggers called contact information. This isn't good method either because it is extremly hard to identify what is what when colliding. You have to also remember that ball is almost all the time colliding with something - floor, wall or eart level. So is there any other method to check what is colliding with what?

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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 I consistently re-size my game window and elements?

  - by Milo

  In my 2D game, I have a flow layout. Inside the flow layout are tables. I have a slider that lets the user make the tables larger or smaller. This makes the background larger or smaller too. Everything should scale proportionally which means the background should stay at the same position when I make things larger, and it almost does. When the scrollbar is at 0, it does exactly this. As the scrollbar gets further down problems arise. I'll toggle the slider maybe 3 times and on the fourth time, the background jumps a little lower on the Y axis. In order to be efficient, I only start rendering the background near the parent of the flow layout. Here it is: void LobbyTableManager::renderBG( GraphicsContext* g, agui::Rectangle& absRect, agui::Rectangle& childRect ) { int cx, cy, cw, ch; g->getClippingRect(cx,cy,cw,ch); g->setClippingRect(absRect.getX(),absRect.getY(),absRect.getWidth(),absRect.getHeight()); float scale = 0.35f; int w = m_bgSprite->getWidth() * getTableScale() * scale; int h = m_bgSprite->getHeight() * getTableScale() * scale; int numX = ceil(absRect.getWidth() / (float)w) + 2; int numY = ceil(absRect.getHeight() / (float)h) + 2; float offsetX = m_activeTables[0]->getLocation().getX() - w; float offsetY = m_activeTables[0]->getLocation().getY() - h; int startY = childRect.getY(); if(moo) { std::cout << "S=" << startY << ","; } int numAttempts = 0; while(startY + h < absRect.getY() && numAttempts < 1000) { startY += h; if(moo) { std::cout << startY << ","; } numAttempts++; } if(moo) { std::cout << "\n"; moo = false; } g->holdDrawing(); for(int i = 0; i < numX; ++i) { for(int j = 0; j < numY; ++j) { g->drawScaledSprite(m_bgSprite,0,0,m_bgSprite->getWidth(),m_bgSprite->getHeight(), absRect.getX() + (i * w) + (offsetX),absRect.getY() + (j * h) + startY,w,h,0); } } g->unholdDrawing(); g->setClippingRect(cx,cy,cw,ch); } The numeric problem seems to be in the value of startY. I outputted startY figuring out its value: As you can see here, this is me only zooming in, pay attention to the final number before the next s=. You'll notice that, what should happen is, the numbers should be linear, ex: -40, -38, -36, -34, -32, -30, etc. As you'll notice, the start numbers linearly correlate ex: 62k, 64k, 66k, 68k, 70k etc.. but the end result is wrong every third or 4th time. Here is most of the resize code: void LobbyTableManager::setTableScale( float scale ) { scale += 0.3f; scale *= 2.0f; agui::Gui* gotGui = getGui(); float scrollRel = m_vScroll->getRelativeValue(); setScale(scale); rescaleTables(); resizeFlow(); if(gotGui) { gotGui->toggleWidgetLocationChanged(false); } updateScrollBars(); float newVal = scrollRel * m_vScroll->getMaxValue(); if((int)(newVal + 0.5f) > (int)newVal) { newVal++; } m_vScroll->setValue(newVal); static int x = 0; x++; moo = true; //std::cout << m_vScroll->getValue() << std::endl; if(gotGui) { gotGui->toggleWidgetLocationChanged(true); } if(gotGui) { gotGui->_widgetLocationChanged(); } } void LobbyTableManager::valueChanged( agui::VScrollBar* source,int val ) { if(getGui()) { getGui()->toggleWidgetLocationChanged(false); } m_flow->setLocation(0,-val); if(getGui()) { getGui()->toggleWidgetLocationChanged(true); getGui()->_widgetLocationChanged(); } }

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• How do I move the camera sideways in Libgdx?

  - by Bubblewrap

  I want to move the camera sideways (strafe). I had the following in mind, but it doesn't look like there are standard methods to achieve this in Libgdx. If I want to move the camera sideways by x, I think I need to do the following: Create a Matrix4 mat Determine the orthogonal vector v between camera.direction and camera.up Translate mat by v*x Multiply camera.position by mat Will this approach do what I think it does, and is it a good way to do it? And how can I do this in libgdx? I get "stuck" at step 2, as I have not found any standard method in Libgdx to calculate an orthogonal vector. EDIT: I think I can use camera.direction.crs(camera.up) to find v. I'll try this approach tonight and see if it works. EDIT2: I got it working and didn't need the matrix after all: Vector3 right = camera.direction.cpy().crs(camera.up).nor(); camera.position.add(right.mul(x));

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• Is finding graph minors without single node pinch points possible?

  - by Alturis

  Is it possible to robustly find all the graph minors within an arbitrary node graph where the pinch points are generally not single nodes? I have read some other posts on here about how to break up your graph into a Hamiltonian cycle and then from that find the graph minors but it seems to be such an algorithm would require that each "room" had "doorways" consisting of single nodes. To explain a bit more a visual aid is necessary. Lets say the nodes below are an example of the typical node graph. What I am looking for is a way to automatically find the different colored regions of the graph (or graph minors)

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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 raycast select a scaled OBB?

  - by user3254944

  I have the OBB picking code to select an OBB with code inspired from Real time Rendering 3 and opengl-tutorial.org. I can successfully select objects that have been moved or rotated. However, I cant correctly select an object that has been scaled. The bounding box scales right, but the I can only select the object in a thin strip on its center. How do I fix the checkForHits() function to allow it to read the scaling that I passed to it in the raycast matrix? void GLWidget::selectObjRaycast() { glm::vec2 mouse = (glm::vec2(mousePos.x(), mousePos.y()) / glm::vec2(this->width(), this->height())) * 2.0f - 1.0f; mouse.y *= -1; glm::mat4 toWorld = glm::inverse(ProjectionM * ViewM); glm::vec4 from = toWorld * glm::vec4(mouse, -1.0f, 1.0f); glm::vec4 to = toWorld * glm::vec4(mouse, 1.0f, 1.0f); from /= from.w; to /= to.w; fromAABB = glm::vec3(from); toAABB = glm::normalize(glm::vec3(to - from)); checkForHits(); } void GLWidget::checkForHits() { for (int i = 0; i < myWin.myEtc->allObj.size(); ++i) //check for hits on each obj's bb { bool miss = 0; float tMin = 0.0f; float tMax = 100000.0f; glm::vec3 bbPos(myWin.myEtc->allObj[i]->raycastM[3].x, myWin.myEtc->allObj[i]->raycastM[3].y, myWin.myEtc->allObj[i]->raycastM[3].z); glm::vec3 delta = bbPos - fromAABB; for (int j = 0; j < 3; ++j) { glm::vec3 axis(myWin.myEtc->allObj[i]->raycastM[j].x, myWin.myEtc->allObj[i]->raycastM[j].y, myWin.myEtc->allObj[i]->raycastM[j].z); float e = glm::dot(axis, delta); float f = glm::dot(toAABB, axis); if (fabs(f) > 0.001f) { float t1 = (e + myWin.myEtc->allObj[i]->bbMin[j]) / f; float t2 = (e + myWin.myEtc->allObj[i]->bbMax[j]) / f; if (t1 > t2) { float w = t1; t1 = t2; t2 = w; } if (t2 < tMax) tMax = t2; if (t1 > tMin) tMin = t1; if (tMax < tMin) miss = 1; } else { if (-e + myWin.myEtc->allObj[i]->bbMin[j] > 0.0f || -e + myWin.myEtc->allObj[i]->bbMax[j] < 0.0f) miss = 1; } } if (miss == 0) { intersection_distance = tMin; myWin.myEtc->sel.push_back(myWin.myEtc->allObj[i]); myWin.myEtc->allObj[i]->highlight = myWin.myGLHelp->highlight; break; } } } void Object::render(glm::mat4 PV) { scaleM = glm::scale(glm::mat4(), s->val_3); r_quat = glm::quat(glm::radians(r->val_3)); rotationM = glm::toMat4(r_quat); translationM = glm::translate(glm::mat4(), t->val_3); transLocal1M = glm::translate(glm::mat4(), -rsPivot->val_3); transLocal2M = glm::translate(glm::mat4(), rsPivot->val_3); raycastM = translationM * transLocal2M * rotationM * scaleM * transLocal1M; // MVP = PV * translationM * transLocal2M * rotationM * scaleM * transLocal1M; }

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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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• 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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• 2D OBB collision detection, resolving collisions?

  - by Milo

  I currently use OBBs and I have a vehicle that is a rigid body and some buildings. Here is my update() private void update() { camera.setPosition((vehicle.getPosition().x * camera.getScale()) - ((getWidth() ) / 2.0f), (vehicle.getPosition().y * camera.getScale()) - ((getHeight() ) / 2.0f)); //camera.move(input.getAnalogStick().getStickValueX() * 15.0f, input.getAnalogStick().getStickValueY() * 15.0f); if(input.isPressed(ControlButton.BUTTON_GAS)) { vehicle.setThrottle(1.0f, false); } if(input.isPressed(ControlButton.BUTTON_BRAKE)) { vehicle.setBrakes(1.0f); } vehicle.setSteering(input.getAnalogStick().getStickValueX()); vehicle.update(16.6666f / 1000.0f); ArrayList<Building> buildings = city.getBuildings(); for(Building b : buildings) { if(vehicle.getRect().overlaps(b.getRect())) { vehicle.update(-17.0f / 1000.0f); break; } } } The collision detection works well. What doesn't is how they are dealt with. My goal is simple. If the vehicle hits a building, it should stop, and never go into the building. When I apply negative torque to reverse the car should not feel buggy and move away from the building. I don't want this to look buggy. This is my rigid body class: class RigidBody extends Entity { //linear private Vector2D velocity = new Vector2D(); private Vector2D forces = new Vector2D(); private float mass; //angular private float angularVelocity; private float torque; private float inertia; //graphical private Vector2D halfSize = new Vector2D(); private Bitmap image; public RigidBody() { //set these defaults so we don't get divide by zeros mass = 1.0f; inertia = 1.0f; } //intialize out parameters public void initialize(Vector2D halfSize, float mass, Bitmap bitmap) { //store physical parameters this.halfSize = halfSize; this.mass = mass; image = bitmap; inertia = (1.0f / 20.0f) * (halfSize.x * halfSize.x) * (halfSize.y * halfSize.y) * mass; RectF rect = new RectF(); float scalar = 10.0f; rect.left = (int)-halfSize.x * scalar; rect.top = (int)-halfSize.y * scalar; rect.right = rect.left + (int)(halfSize.x * 2.0f * scalar); rect.bottom = rect.top + (int)(halfSize.y * 2.0f * scalar); setRect(rect); } public void setLocation(Vector2D position, float angle) { getRect().set(position, getWidth(), getHeight(), angle); } public Vector2D getPosition() { return getRect().getCenter(); } @Override public void update(float timeStep) { //integrate physics //linear Vector2D acceleration = Vector2D.scalarDivide(forces, mass); velocity = Vector2D.add(velocity, Vector2D.scalarMultiply(acceleration, timeStep)); Vector2D c = getRect().getCenter(); c = Vector2D.add(getRect().getCenter(), Vector2D.scalarMultiply(velocity , timeStep)); setCenter(c.x, c.y); forces = new Vector2D(0,0); //clear forces //angular float angAcc = torque / inertia; angularVelocity += angAcc * timeStep; setAngle(getAngle() + angularVelocity * timeStep); torque = 0; //clear torque } //take a relative Vector2D and make it a world Vector2D public Vector2D relativeToWorld(Vector2D relative) { Matrix mat = new Matrix(); float[] Vector2Ds = new float[2]; Vector2Ds[0] = relative.x; Vector2Ds[1] = relative.y; mat.postRotate(JMath.radToDeg(getAngle())); mat.mapVectors(Vector2Ds); return new Vector2D(Vector2Ds[0], Vector2Ds[1]); } //take a world Vector2D and make it a relative Vector2D public Vector2D worldToRelative(Vector2D world) { Matrix mat = new Matrix(); float[] Vectors = new float[2]; Vectors[0] = world.x; Vectors[1] = world.y; mat.postRotate(JMath.radToDeg(-getAngle())); mat.mapVectors(Vectors); return new Vector2D(Vectors[0], Vectors[1]); } //velocity of a point on body public Vector2D pointVelocity(Vector2D worldOffset) { Vector2D tangent = new Vector2D(-worldOffset.y, worldOffset.x); return Vector2D.add( Vector2D.scalarMultiply(tangent, angularVelocity) , velocity); } public void applyForce(Vector2D worldForce, Vector2D worldOffset) { //add linear force forces = Vector2D.add(forces ,worldForce); //add associated torque torque += Vector2D.cross(worldOffset, worldForce); } @Override public void draw( GraphicsContext c) { c.drawRotatedScaledBitmap(image, getPosition().x, getPosition().y, getWidth(), getHeight(), getAngle()); } } Essentially, when any rigid body hits a building it should exhibit the same behavior. How is collision solving usually done? Thanks

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