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• Java Slick2d - Mouse picking how to take into account camera

  - by Corey

  When I move it it obviously changes the viewport so my mouse picking is off. My camera is just a float x and y and I use g.translate(-cam.cameraX+400, -cam.cameraY+300); to translate the graphics. I have the numbers hard coded just for testing purposes. How would I take into account the camera so my mouse picking works correctly. double mousetileX = Math.floor((double)mouseX/tiles.tileWidth); double mousetileY = Math.floor((double)mouseY/tiles.tileHeight); double playertileX = Math.floor(playerX/tiles.tileWidth); double playertileY = Math.floor(playerY/tiles.tileHeight); double lengthX = Math.abs((float)playertileX - mousetileX); double lengthY = Math.abs((float)playertileY - mousetileY); double distance = Math.sqrt((lengthX*lengthX)+(lengthY*lengthY)); if(input.isMousePressed(Input.MOUSE_LEFT_BUTTON) && distance < 4) { if(tiles.map[(int)mousetileX][(int)mousetileY] == 1) { tiles.map[(int)mousetileX][(int)mousetileY] = 0; } } That is my mouse picking code

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• How to scroll hex tiles?

  - by Chris Evans

  I don't seem to be able to find an answer to this one. I have a map of hex tiles. I wish to implement scrolling. Code at present: drawTilemap = function() { actualX = Math.floor(viewportX / hexWidth); actualY = Math.floor(viewportY / hexHeight); offsetX = -(viewportX - (actualX * hexWidth)); offsetY = -(viewportY - (actualY * hexHeight)); for(i = 0; i < (10); i++) { for(j = 0; j < 10; j++) { if(i % 2 == 0) { x = (hexOffsetX * i) + offsetX; y = j * sourceHeight; } else { x = (hexOffsetX * i) + offsetX; y = hexOffsetY + (j * sourceHeight); } var tileselected = mapone[actualX + i][j]; drawTile(x, y, tileselected); } } } The code I've written so far only handles X movement. It doesn't yet work the way it should do. If you look at my example on jsfiddle.net below you will see that when moving to the right, when you get to the next hex tile along, there is a problem with the X position and calculations that have taken place. It seems it is a simple bit of maths that is missing. Unfortunately I've been unable to find an example that includes scrolling yet. http://jsfiddle.net/hd87E/1/ Make sure there is no horizontal scroll bar then trying moving right using the - right arrow on the keyboard. You will see the problem as you reach the end of the first tile. Apologies for the horrid code, I'm learning! Cheers

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• How to handle animations?

  - by Bane

  I am coding a simple 2D engine to be used with HTML5. I already have classes such as Picture, Scene, Camera and Renderer, but now I need to work on Animations. Picture is basocally a wrapper for a normal image object, with it's own draw method, but this is unrelated, I'm interested in how animation in 2D games is usually done. What I planned to do, is to have the Animation class as well act like a wrapper for a few image objects, and then have methods such as getCurrentImage, next and animate (which would use intervals to quickly change the current image). I meant to feed the animation a couple of PNG's at inicialisation. Is quickly swapping PNG images acceptable for 2D animation? Are there some standard ways of doing this, or are there flaws in my ways?

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• Component-based Rendering

  - by Kikaimaru

  I have component Renderer, that Draws Texture2D (or sprite) According to component-based architecture i should have only method OnUpdate, and there should be my rendering code, something like spriteBatch.Draw(Texture, Vector2.Zero, Color.White) But first I need to do spriteBatch.Begin();. Where should i call it? And how can I make sure it's called before any Renderer components OnUpdate method? (i need to do more stuff then just Begin() i also need to set right rendertarget for camera etc.)

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

  - by sebf

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

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• Behaviour tree code example?

  - by jokoon

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

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• 2D Animation Smoothness - Delta time vs. Kinematics

  - by viperld002

  I'm animating a sprite in 2D with key frames of rotation and xy-positions. I've recently had a discussion with someone saying that when the device (happens to be an iPad using cocos2D) hits a performance bump due to whatever else the user may be doing, lag will arise and that the best way to fight it is to not use actual positions, but velocities, accelerations and torques with kinematics. His message is to evaluate the positions and rotations from these speeds at the current point in time. I've never experienced a situation where I've heard of using kinematics to stem lag in 2D animations and am not sure of how effective it could be. Also, it seems to be overkill. The application is not networked so it's all running on a local device. The desired effect is that the animation always plays as closely as it can to the target frame rate. Wouldn't the technique suffer the same problems as just using the time since the last frame or a fixed time step since the kinematics would also require some time value to perform the calculation? What techniques could you suggest to best achieve the desired effect? EDIT 1 Thank you for your responses, they are very illuminating. I want to clarify my question before choosing an answer however, to make sure that this post really serves it's purpose. I have a sprite of a ball, and a text file with 3 arrays worth of information (rotation,translations x, translations y) with each unit of information existing as a key frame to be stepped through (0 to 49 and back to 0 to replay it again). I have this playing by interpolating from the current key frame to the next, every n-units of time. The animation is visibly correct when compared to a video I was given of it, and it is smooth because of the interpolations between the key frames. This is the existing state of the project. There are no physics simulated, only a static animation of a ball moving in a way an artist specifically designed. Should I, instead of rotation in degrees and translations by positions in space, derive velocities, accelerations and torques to express this static animation as a function of time? As in, position now = foo(time now), where foo uses kinematics.

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• My frustum culling is culling from the wrong point [SOLVED]

  - by Xbetas

  I'm having problems with my frustum being in the wrong origin. It follows the rotation of my camera but not the position. In my camera class I'm generating a view-matrix: void Camera::Update() { UpdateViewMatrix(); glMatrixMode(GL_MODELVIEW); //glLoadIdentity(); glLoadMatrixf(GetViewMatrix().m); } Then extracting the planes using the projection matrix and modelview matrix: void UpdateFrustum() { Matrix4x4 projection, model, clip; glGetFloatv(GL_PROJECTION_MATRIX, projection.m); glGetFloatv(GL_MODELVIEW_MATRIX, model.m); clip = model * projection; m_Planes[RIGHT][0] = clip.m[ 3] - clip.m[ 0]; m_Planes[RIGHT][1] = clip.m[ 7] - clip.m[ 4]; m_Planes[RIGHT][2] = clip.m[11] - clip.m[ 8]; m_Planes[RIGHT][3] = clip.m[15] - clip.m[12]; NormalizePlane(RIGHT); m_Planes[LEFT][0] = clip.m[ 3] + clip.m[ 0]; m_Planes[LEFT][1] = clip.m[ 7] + clip.m[ 4]; m_Planes[LEFT][2] = clip.m[11] + clip.m[ 8]; m_Planes[LEFT][3] = clip.m[15] + clip.m[12]; NormalizePlane(LEFT); m_Planes[BOTTOM][0] = clip.m[ 3] + clip.m[ 1]; m_Planes[BOTTOM][1] = clip.m[ 7] + clip.m[ 5]; m_Planes[BOTTOM][2] = clip.m[11] + clip.m[ 9]; m_Planes[BOTTOM][3] = clip.m[15] + clip.m[13]; NormalizePlane(BOTTOM); m_Planes[TOP][0] = clip.m[ 3] - clip.m[ 1]; m_Planes[TOP][1] = clip.m[ 7] - clip.m[ 5]; m_Planes[TOP][2] = clip.m[11] - clip.m[ 9]; m_Planes[TOP][3] = clip.m[15] - clip.m[13]; NormalizePlane(TOP); m_Planes[NEAR][0] = clip.m[ 3] + clip.m[ 2]; m_Planes[NEAR][1] = clip.m[ 7] + clip.m[ 6]; m_Planes[NEAR][2] = clip.m[11] + clip.m[10]; m_Planes[NEAR][3] = clip.m[15] + clip.m[14]; NormalizePlane(NEAR); m_Planes[FAR][0] = clip.m[ 3] - clip.m[ 2]; m_Planes[FAR][1] = clip.m[ 7] - clip.m[ 6]; m_Planes[FAR][2] = clip.m[11] - clip.m[10]; m_Planes[FAR][3] = clip.m[15] - clip.m[14]; NormalizePlane(FAR); } void NormalizePlane(int side) { float length = 1.0/(float)sqrt(m_Planes[side][0] * m_Planes[side][0] + m_Planes[side][1] * m_Planes[side][1] + m_Planes[side][2] * m_Planes[side][2]); m_Planes[side][0] *= length; m_Planes[side][1] *= length; m_Planes[side][2] *= length; m_Planes[side][3] *= length; } And check against it with: bool PointInFrustum(float x, float y, float z) { for(int i = 0; i < 6; i++) { if( m_Planes[i][0] * x + m_Planes[i][1] * y + m_Planes[i][2] * z + m_Planes[i][3] <= 0 ) return false; } return true; } Then i render using: camera->Update(); UpdateFrustum(); int numCulled = 0; for(int i = 0; i < (int)meshes.size(); i++) { if(!PointInFrustum(meshCenter.x, meshCenter.y, meshCenter.z)) { meshes[i]->SetDraw(false); numCulled++; } else meshes[i]->SetDraw(true); } Matrices look like (Camera is at (5, 0, 0)): ModelView [0,0,0.99,0] [0,1,0,0] [-0.99,0,0,0] [0,0,-5,1] Projection [0.814,0,0,0] [0,1.303,0,0] [0,0,-1,0] [0,0,-0.02,0] Clip [0,0,-1,-0.999] [0,1.30,0,0] [-0.814,0,0,0] [0,0,4.98,4.99] What am i doing wrong?

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• 2D SAT Collision Detection not working when using certain polygons (With example)

  - by sFuller

  My SAT algorithm falsely reports that collision is occurring when using certain polygons. I believe this happens when using a polygon that does not contain a right angle. Here is a simple diagram of what is going wrong: Here is the problematic code: std::vector<vec2> axesB = polygonB->GetAxes(); //loop over axes B for(int i = 0; i < axesB.size(); i++) { float minA,minB,maxA,maxB; polygonA->Project(axesB[i],&minA,&maxA); polygonB->Project(axesB[i],&minB,&maxB); float intervalDistance = polygonA->GetIntervalDistance(minA, maxA, minB, maxB); if(intervalDistance >= 0) return false; //Collision not occurring } This function retrieves axes from the polygon: std::vector<vec2> Polygon::GetAxes() { std::vector<vec2> axes; for(int i = 0; i < verts.size(); i++) { vec2 a = verts[i]; vec2 b = verts[(i+1)%verts.size()]; vec2 edge = b-a; axes.push_back(vec2(-edge.y,edge.x).GetNormailzed()); } return axes; } This function returns the normalized vector: vec2 vec2::GetNormailzed() { float mag = sqrt( x*x + y*y ); return *this/mag; } This function projects a polygon onto an axis: void Polygon::Project(vec2* axis, float* min, float* max) { float d = axis->DotProduct(&verts[0]); float _min = d; float _max = d; for(int i = 1; i < verts.size(); i++) { d = axis->DotProduct(&verts[i]); _min = std::min(_min,d); _max = std::max(_max,d); } *min = _min; *max = _max; } This function returns the dot product of the vector with another vector. float vec2::DotProduct(vec2* other) { return (x*other->x + y*other->y); } Could anyone give me a pointer in the right direction to what could be causing this bug? Edit: I forgot this function, which gives me the interval distance: float Polygon::GetIntervalDistance(float minA, float maxA, float minB, float maxB) { float intervalDistance; if (minA < minB) { intervalDistance = minB - maxA; } else { intervalDistance = minA - maxB; } return intervalDistance; //A positive value indicates this axis can be separated. } Edit 2: I have recreated the problem in HTML5/Javascript: Demo

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• how can i get rotation vector from matrix4x4 in xna?

  - by mr.Smyle

  i want to get rotation vector from matrix to realize some parent-children system for models. Matrix bonePos = link.Bone.Transform * World; Matrix m = Matrix.CreateTranslation(link.Offset) * Matrix.CreateScale(link.gameObj.Scale.X, link.gameObj.Scale.Y, link.gameObj.Scale.Z) * Matrix.CreateFromYawPitchRoll(MathHelper.ToRadians(link.gameObj.Rotation.Y), MathHelper.ToRadians(link.gameObj.Rotation.X), MathHelper.ToRadians(link.gameObj.Rotation.Z)) //need rotation vector from bone matrix here (now it's global model rotation vector) * Matrix.CreateFromYawPitchRoll(MathHelper.ToRadians(Rotation.Y), MathHelper.ToRadians(Rotation.X), MathHelper.ToRadians(Rotation.Z)) * Matrix.CreateTranslation(bonePos.Translation); link.gameObj.World = m; where : link - struct with children model settings, like position, rotation etc. And link.Bone - Parent Bone

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• OpenGL VertexBuffer won'e render in GLFW3

  - by sm81095

  So I have started to try to learn OpenGL, and I decided to use GLFW to assist in window creation. The problem is, since GLFW3 is so new, there are no tutorials on it yet and how to use it with modern OpenGL (3.3, specifically). Using the GLFW3 tutorial found on the website, which uses older OpenGL rendering (glBegin(GL_TRIANGLES), glVertex3f()), and such, I can get a triangle to render to the screen. The problem is, using new OpenGL, I can't get the same triangle to render to the screen. I am new to OpenGL, and GLFW3 is new to most people, so I may be completely missing something obvious, but here is my code: static const GLuint g_vertex_buffer_data[] = { -1.0f, -1.0f, 0.0f, 1.0f, -1.0f, 0.0f, 0.0f, 1.0f, 0.0f }; int main(void) { GLFWwindow* window; if(!glfwInit()) { fprintf(stderr, "Failed to initialize GLFW."); return -1; } glfwWindowHint(GLFW_SAMPLES, 4); glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3); glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3); glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE); glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE); window = glfwCreateWindow(800, 600, "Test Window", NULL, NULL); if(!window) { glfwTerminate(); fprintf(stderr, "Failed to create a GLFW window"); return -1; } glfwMakeContextCurrent(window); glewExperimental = GL_TRUE; GLenum err = glewInit(); if(err != GLEW_OK) { glfwTerminate(); fprintf(stderr, "Failed to initialize GLEW"); fprintf(stderr, (char*)glewGetErrorString(err)); return -1; } GLuint VertexArrayID; glGenVertexArrays(1, &VertexArrayID); glBindVertexArray(VertexArrayID); GLuint programID = LoadShaders("SimpleVertexShader.glsl", "SimpleFragmentShader.glsl"); GLuint vertexBuffer; glGenBuffers(1, &vertexBuffer); glBindBuffer(GL_ARRAY_BUFFER, vertexBuffer); glBufferData(GL_ARRAY_BUFFER, sizeof(g_vertex_buffer_data), g_vertex_buffer_data, GL_STATIC_DRAW); while(!glfwWindowShouldClose(window)) { glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); glUseProgram(programID); glEnableVertexAttribArray(0); glBindBuffer(GL_ARRAY_BUFFER, vertexBuffer); glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, (void*)0); glDrawArrays(GL_TRIANGLES, 0, 3); glDisableVertexAttribArray(0); glfwSwapBuffers(window); glfwPollEvents(); } glDeleteBuffers(1, &vertexBuffer); glDeleteProgram(programID); glfwDestroyWindow(window); glfwTerminate(); exit(EXIT_SUCCESS); } I know it is not my shaders, they are super simple and I've checked them against GLFW 2.7 so I know that they work. I'm assuming that I've missed something crucial to using the OpenGL context with GLFW3, so any help locating the problem would be greatly appreciated.

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• Change alpha to a Frame in libgdx

  - by Rudy_TM

  I have this batch.draw(currentFrame, x, y, this.parent.originX, this.parent.originY, this.parent.width, this.parent.height, this.scaleX, this.scaleY,this.rotation); I want to apply the alpha that it gets from the method, but theres is not overload from the SpriteBatch class that takes the alpha value, is there some wey to apply it? (i did it this way, because this are animation, and i wanted to control them) in my static ones i apply sprite.draw(SpriteBatch, alpha) Thanks

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• Maya Animated Character export for XNA 4.0 problem

  - by FahidK

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

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• How to calculate vertext normals for a mesh in Java in OpenGL ES application?

  - by alan mc

  Can some one point me to Java code ( in Java not C or C++) that calculates all the normals for all the vertices of a mesh for OpenGL ES application. I need this for lighting. Lets say I have a cube with following vertices and indices: float vertices[] = { -width, -height, -depth, // 0 width, -height, -depth, // 1 width, height, -depth, // 2 -width, height, -depth, // 3 -width, -height, depth, // 4 width, -height, depth, // 5 width, height, depth, // 6 -width, height, depth // 7 }; short indices[] = { 0, 2, 1, 0, 3, 2, 1,2,6, 6,5,1, 4,5,6, 6,7,4, 2,3,6, 6,3,7, 0,7,3, 0,4,7, 0,1,5, 0,5,4 }; In above specific example how many normals we need ?

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• Import FBX with multiple meshes into UDK

  - by Tom

  I used this script to generate a few buildings that I was hoping to import into UDK. Each building is made of about 1000 separate objects. When I export a building as FBX and import the file into UDK it breaks it up into its individual objects again, so I was wondering how I would avoid this. Whether there was a tool to combine all of the objects into one mesh automatically before exporting or if I could prevent UDK from breaking them upon import.

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• Lighting with VBO

  - by nkint

  I'm using a Java JOGL wrapper called processing.org. I have coded some enviroment on it and I'm quite proud of it even if it has some ready stuffs that I didn't know anything about it (==LIGHTS). Then, for some geometry, I've decided to use a VBO. I had to pass in the hard way and recode all lights. But I can't achieve the same result. This is the original light system: And this with VBO: With this code: Vec3D l; gl.glEnable(GL.GL_LIGHTING); gl.glEnable(GL.GL_LIGHT0); gl.glEnable(GL.GL_COLOR_MATERIAL); gl.glMaterialfv(GL.GL_FRONT_AND_BACK, GL.GL_AMBIENT, new float[]{0.8f,0f,0f}, 0); l = new Vec3D(0,0,-10); gl.glColor3f(0.8f,0f,0f); gl.glLightfv(GL.GL_LIGHT0, GL.GL_POSITION, new float[] { l.x, l.y, l.z, 0 }, 0); gl.glLightfv(GL.GL_LIGHT0, GL.GL_SPOT_DIRECTION, new float[] { 1, 1, 1, 1 }, 0); I can't achive the same light, the same color material, and the same wireframe stuffs. If needed I can also post the code I use for VBO, but it is quite standard vertex array grabbed on the net that uses glDrawArrays

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• Why does my program stutter so much?

  - by user36322

  I've been very frustrated trying to solve this. I've looked it up, and all the answers are the same: set IsFixedTimeStep = false. This doesn't help me at all, the program is still jittery and stutters. I have absolutely no idea what is going on, can you guys help? Code for movement (objects is a list): speed = Math.Min(speed + (speedIncrement * gameTime.ElapsedGameTime.Milliseconds / 200), maxSpeed); for (int i = objects.Count - 1; i >= 0; i--) { objects[i].rect.Y += (int)(speed * gameTime.ElapsedGameTime.Milliseconds); //Check if the object is past the screen. If it is, remove it if (objects[i].rect.Y > screenHeight) { objects.Remove(objects[i]); } }

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• Rotating a cube using jBullet collisions

  - by Kenneth Bray

  How would one go about rotating/flipping a cube with the physics of jBullet? Here is my Draw method for my cube object: public void Draw() { // center point posX, posY, posZ float radius = .25f;//size / 2; glPushMatrix(); glBegin(GL_QUADS); //top { glColor3f(5.0f,1.0f,5.0f); // white glVertex3f(posX + radius, posY + radius, posZ - radius); glVertex3f(posX - radius, posY + radius, posZ - radius); glVertex3f(posX - radius, posY + radius, posZ + radius); glVertex3f(posX + radius, posY + radius, posZ + radius); } //bottom { glColor3f(1.0f,1.0f,0.0f); // ?? color glVertex3f(posX + radius, posY - radius, posZ + radius); glVertex3f(posX - radius, posY - radius, posZ + radius); glVertex3f(posX - radius, posY - radius, posZ - radius); glVertex3f(posX + radius, posY - radius, posZ - radius); } //right side { glColor3f(1.0f,0.0f,1.0f); // ?? color glVertex3f(posX + radius, posY + radius, posZ + radius); glVertex3f(posX + radius, posY - radius, posZ + radius); glVertex3f(posX + radius, posY - radius, posZ - radius); glVertex3f(posX + radius, posY + radius, posZ - radius); } //left side { glColor3f(0.0f,1.0f,1.0f); // ?? color glVertex3f(posX - radius, posY + radius, posZ - radius); glVertex3f(posX - radius, posY - radius, posZ - radius); glVertex3f(posX - radius, posY - radius, posZ + radius); glVertex3f(posX - radius, posY + radius, posZ + radius); } //front side { glColor3f(0.0f,0.0f,1.0f); // blue glVertex3f(posX + radius, posY + radius, posZ + radius); glVertex3f(posX - radius, posY + radius, posZ + radius); glVertex3f(posX - radius, posY - radius, posZ + radius); glVertex3f(posX + radius, posY - radius, posZ + radius); } //back side { glColor3f(0.0f,1.0f,0.0f); // green glVertex3f(posX + radius, posY - radius, posZ - radius); glVertex3f(posX - radius, posY - radius, posZ - radius); glVertex3f(posX - radius, posY + radius, posZ - radius); glVertex3f(posX + radius, posY + radius, posZ - radius); } glEnd(); glPopMatrix(); Update(); } This is my update method for the cube position: public void Update() { Transform trans = new Transform(); cubeRigidBody.getMotionState().getWorldTransform(trans); posX = trans.origin.x; posY = trans.origin.y; posZ = trans.origin.z; Quat4f outRot = new Quat4f(); trans.getRotation(outRot); rotX = outRot.x; rotY = outRot.y; rotZ = outRot.z; rotW = outRot.w; } I am assuming I need to use glrotatef, but it does not seem to work at all when I try that.. this is how I have tried to rotate the cubes: GL11.glRotatef(rotW, rotX, 0.0f, 0.0f); GL11.glRotatef(rotW, 0.0f, rotY, 0.0f); GL11.glRotatef(rotW, 0.0f, 0.0f, rotZ);

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• What functionality should I use in OpenGL 2.0?

  - by Jeffrey

  Considering OpenGL 2.1, we all know that glBegin and glEnd are the devil. Should I use only VBO to render 3d primitives (I can't find VAO in that version, weren't there already?)? Should I still use the matrix stack (why not?)? Should I still use glFrustum? Can I take advantage of shaders in GLSL 1.20? Where can I find a tutorial for VBO in OpenGL 2.1 and the "correct" way of programming in it? Also how am I supposed to animate something. Like a cube moving around an object or a player moving in the scene (static vbo data + shader?)? Note: Take your time to answer this question, I'll accept an answer tomorrow.

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• How to get a point to the left/right of a vector

  - by MulletDevil

  I have a position vector of a point in space and a quaternion for it's rotation. What i'm trying to calculate is a point too the left and a point to the right. I have the position and rotation(quaternion) of the red dot. What I want is to get the position of the green dots. I have a float value for the distance I want these points to be. With only the position and rotation is it possible to get a unit direction vector pointing left/right which I can multiply by my float value? Edit: I also know the original direction vector.

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• GLSL: Strange light reflections

  - by Tom

  According to this tutorial I'm trying to make a normal mapping using GLSL, but something is wrong and I can't find the solution. The output render is in this image: Image1 in this image is a plane with two triangles and each of it is different illuminated (that is bad). The plane has 6 vertices. In the upper left side of this plane are 2 identical vertices (same in the lower right). Here are some vectors same for each vertice: normal vector = 0, 1, 0 (red lines on image) tangent vector = 0, 0,-1 (green lines on image) bitangent vector = -1, 0, 0 (blue lines on image) here I have one question: The two identical vertices does need to have the same tangent and bitangent? I have tried to make other values to the tangents but the effect was still similar. Here are my shaders Vertex shader: #version 130 // Input vertex data, different for all executions of this shader. in vec3 vertexPosition_modelspace; in vec2 vertexUV; in vec3 vertexNormal_modelspace; in vec3 vertexTangent_modelspace; in vec3 vertexBitangent_modelspace; // Output data ; will be interpolated for each fragment. out vec2 UV; out vec3 Position_worldspace; out vec3 EyeDirection_cameraspace; out vec3 LightDirection_cameraspace; out vec3 LightDirection_tangentspace; out vec3 EyeDirection_tangentspace; // Values that stay constant for the whole mesh. uniform mat4 MVP; uniform mat4 V; uniform mat4 M; uniform mat3 MV3x3; uniform vec3 LightPosition_worldspace; void main(){ // Output position of the vertex, in clip space : MVP * position gl_Position = MVP * vec4(vertexPosition_modelspace,1); // Position of the vertex, in worldspace : M * position Position_worldspace = (M * vec4(vertexPosition_modelspace,1)).xyz; // Vector that goes from the vertex to the camera, in camera space. // In camera space, the camera is at the origin (0,0,0). vec3 vertexPosition_cameraspace = ( V * M * vec4(vertexPosition_modelspace,1)).xyz; EyeDirection_cameraspace = vec3(0,0,0) - vertexPosition_cameraspace; // Vector that goes from the vertex to the light, in camera space. M is ommited because it's identity. vec3 LightPosition_cameraspace = ( V * vec4(LightPosition_worldspace,1)).xyz; LightDirection_cameraspace = LightPosition_cameraspace + EyeDirection_cameraspace; // UV of the vertex. No special space for this one. UV = vertexUV; // model to camera = ModelView vec3 vertexTangent_cameraspace = MV3x3 * vertexTangent_modelspace; vec3 vertexBitangent_cameraspace = MV3x3 * vertexBitangent_modelspace; vec3 vertexNormal_cameraspace = MV3x3 * vertexNormal_modelspace; mat3 TBN = transpose(mat3( vertexTangent_cameraspace, vertexBitangent_cameraspace, vertexNormal_cameraspace )); // You can use dot products instead of building this matrix and transposing it. See References for details. LightDirection_tangentspace = TBN * LightDirection_cameraspace; EyeDirection_tangentspace = TBN * EyeDirection_cameraspace; } Fragment shader: #version 130 // Interpolated values from the vertex shaders in vec2 UV; in vec3 Position_worldspace; in vec3 EyeDirection_cameraspace; in vec3 LightDirection_cameraspace; in vec3 LightDirection_tangentspace; in vec3 EyeDirection_tangentspace; // Ouput data out vec3 color; // Values that stay constant for the whole mesh. uniform sampler2D DiffuseTextureSampler; uniform sampler2D NormalTextureSampler; uniform sampler2D SpecularTextureSampler; uniform mat4 V; uniform mat4 M; uniform mat3 MV3x3; uniform vec3 LightPosition_worldspace; void main(){ // Light emission properties // You probably want to put them as uniforms vec3 LightColor = vec3(1,1,1); float LightPower = 40.0; // Material properties vec3 MaterialDiffuseColor = texture2D( DiffuseTextureSampler, vec2(UV.x,-UV.y) ).rgb; vec3 MaterialAmbientColor = vec3(0.1,0.1,0.1) * MaterialDiffuseColor; //vec3 MaterialSpecularColor = texture2D( SpecularTextureSampler, UV ).rgb * 0.3; vec3 MaterialSpecularColor = vec3(0.5,0.5,0.5); // Local normal, in tangent space. V tex coordinate is inverted because normal map is in TGA (not in DDS) for better quality vec3 TextureNormal_tangentspace = normalize(texture2D( NormalTextureSampler, vec2(UV.x,-UV.y) ).rgb*2.0 - 1.0); // Distance to the light float distance = length( LightPosition_worldspace - Position_worldspace ); // Normal of the computed fragment, in camera space vec3 n = TextureNormal_tangentspace; // Direction of the light (from the fragment to the light) vec3 l = normalize(LightDirection_tangentspace); // Cosine of the angle between the normal and the light direction, // clamped above 0 // - light is at the vertical of the triangle -> 1 // - light is perpendicular to the triangle -> 0 // - light is behind the triangle -> 0 float cosTheta = clamp( dot( n,l ), 0,1 ); // Eye vector (towards the camera) vec3 E = normalize(EyeDirection_tangentspace); // Direction in which the triangle reflects the light vec3 R = reflect(-l,n); // Cosine of the angle between the Eye vector and the Reflect vector, // clamped to 0 // - Looking into the reflection -> 1 // - Looking elsewhere -> < 1 float cosAlpha = clamp( dot( E,R ), 0,1 ); color = // Ambient : simulates indirect lighting MaterialAmbientColor + // Diffuse : "color" of the object MaterialDiffuseColor * LightColor * LightPower * cosTheta / (distance*distance) + // Specular : reflective highlight, like a mirror MaterialSpecularColor * LightColor * LightPower * pow(cosAlpha,5) / (distance*distance); //color.xyz = E; //color.xyz = LightDirection_tangentspace; //color.xyz = EyeDirection_tangentspace; } I have replaced the original color value by EyeDirection_tangentspace vector and then I got other strange effect but I can not link the image (not eunogh reputation) Is it possible that with this shaders is something wrong, or maybe in other place in my code e.g with my matrices? SOLVED Solved... 3 days needed for changing one letter from this: glBindBuffer(GL_ARRAY_BUFFER, vbo); glVertexAttribPointer ( 4, // attribute 3, // size GL_FLOAT, // type GL_FALSE, // normalized? sizeof(VboVertex), // stride (void*)(12*sizeof(float)) // array buffer offset ); to this: glBindBuffer(GL_ARRAY_BUFFER, vbo); glVertexAttribPointer ( 4, // attribute 3, // size GL_FLOAT, // type GL_FALSE, // normalized? sizeof(VboVertex), // stride (void*)(11*sizeof(float)) // array buffer offset ); see difference? :)

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• What should I worry about when changing OpenGL origin to upper left of screen?

  - by derivative

  For self education, I'm writing a 2D platformer engine in C++ using SDL / OpenGL. I initially began with pure SDL using the tutorials on sdltutorials.com and lazyfoo.net, but I'm now rendering in an OpenGL context (specifically immediate mode but I'm learning about VAOs/VBOs) and using SDL for interface, audio, etc. SDL uses a coordinate system with the origin in the upper left of the screen and the positive y-axis pointing down. It's easy to set up my orthographic projection in OpenGL to mirror this. I know that texture coordinates are a right-hand system with values from 0 to 1 -- flipping the texture vertically before rendering (well, flip the file before loading) yields textures that render correctly... which is fine if I'm drawing the entire texture, but ultimately I'll be using tilesets and can imagine problems. What should I be concerned about in terms of rendering when I do this? If anybody has any advice or they've done this themselves and can point out future pitfalls, that would be great, but really any thoughts would be appreciated.

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• How do I simulate the mouse and keyboard using C# or C++?

  - by Art

  I want to start develop for Kinect, but hardest theme for it - how to send keyboard and mouse input to any application. In previous question I got an advice to develop my own driver for this devices, but this will take a while. I imagine application like a gate, that can translate SendMessage's into system wide input or driver application with API to send this inputs. So I wonder, is there are drivers or simulators that can interact with C# or C++? Small edition: SendMessage, PostMessage, keybd_event will work only on Windows application with common messages loop. So I need driver application that will work on low, kernel, level.

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• Check for bodies within a specific circle in Box2D

  - by ltjax

  I'm trying to find positions to insert new bodies into my world. For that, I'd like to have a "free" spot where this body wouldn't overlap with anything else. So my plan was to sample "random" positions and check whether they overlap with my "potential" new body. Since my bodies are always circular, I'd need to test within a given circle. So far, the only way to use box2d for this seems to use b2World::QueryAABB around my circle and manually doing an overlap test with all the fixtures it gives me (Box2D doesn't event seem to allow me to tap into its overlapping tests?!). It seems to me like Box2D should already provide such functionality - is there a way that lets me do this without reinventing most of the wheel again?

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• exact point on a rotating sphere

  - by nkint

  I have a sphere that represents the Earth textured with real pictures. It's rotating around the x axis, and when user click down it has to show me the exact place he clicked on. For example if he clicked on Singapore the system should be able to: understand that user clicked on the sphere (OK, I'll do it with unProject) understand where user clicked on the sphere (ray-sphere collision?) and take into account the rotation transform sphere-coordinate to some coordinate system good for some web-api service ask to api (OK, this is the simpler thing for me ;-) some advice?

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