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• How does interpolation actually work to smooth out an object's movement?

  - by user22241

  I've asked a few similar questions over the past 8 months or so with no real joy, so I am going make the question more general. I have an Android game which is OpenGL ES 2.0. within it I have the following Game Loop: My loop works on a fixed time step principle (dt = 1 / ticksPerSecond) loops=0; while(System.currentTimeMillis() > nextGameTick && loops < maxFrameskip){ updateLogic(dt); nextGameTick+=skipTicks; timeCorrection += (1000d/ticksPerSecond) % 1; nextGameTick+=timeCorrection; timeCorrection %=1; loops++; } render(); My intergration works like this: sprite.posX+=sprite.xVel*dt; sprite.posXDrawAt=sprite.posX*width; Now, everything works pretty much as I would like. I can specify that I would like an object to move across a certain distance (screen width say) in 2.5 seconds and it will do just that. Also because of the frame skipping that I allow in my game loop, I can do this on pretty much any device and it will always take 2.5 seconds. Problem However, the problem is that when a render frame skips, the graphic stutter. It's extremely annoying. If I remove the ability to skip frames, then everything is smooth as you like, but will run at different speeds on different devices. So it's not an option. I'm still not sure why the frame skips, but I would like to point out that this is Nothing to do with poor performance, I've taken the code right back to 1 tiny sprite and no logic (apart from the logic required to move the sprite) and I still get skipped frames. And this is on a Google Nexus 10 tablet (and as mentioned above, I need frame skipping to keep the speed consistent across devices anyway). So, the only other option I have is to use interpolation (or extrapolation), I've read every article there is out there but none have really helped me to understand how it works and all of my attempted implementations have failed. Using one method I was able to get things moving smoothly but it was unworkable because it messed up my collision. I can foresee the same issue with any similar method because the interpolation is passed to (and acted upon within) the rendering method - at render time. So if Collision corrects position (character now standing right next to wall), then the renderer can alter it's position and draw it in the wall. So I'm really confused. People have said that you should never alter an object's position from within the rendering method, but all of the examples online show this. So I'm asking for a push in the right direction, please do not link to the popular game loop articles (deWitters, Fix your timestep, etc) as I've read these multiple times. I'm not asking anyone to write my code for me. Just explain please in simple terms how Interpolation actually works with some examples. I will then go and try to integrate any ideas into my code and will ask more specific questions if need-be further down the line. (I'm sure this is a problem many people struggle with).

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• C++ OpenGL wireframe cube rendering blank

  - by caleb.breckon

  I'm just trying to draw a bunch of lines that make up a "cube". I can't for the life of me figure out why this is producing a black screen. The debugger does not break at any point. I'm sure it's a problem with my pointers, as I'm only decent at them in regular c++ and in OpenGL it gets even worse. const char* vertexSource = "#version 150\n" "in vec3 position;" "void main() {" " gl_Position = vec4(position, 1.0);" "}"; const char* fragmentSource = "#version 150\n" "out vec4 outColor;" "void main() {" " outColor = vec4(1.0, 1.0, 1.0, 1.0);" "}"; int main() { initializeGLFW(); // Initialize GLEW glewExperimental = GL_TRUE; glewInit(); // Create Vertex Array Object GLuint vao; glGenVertexArrays(1, &vao); glBindVertexArray(vao); // Create a Vertex Buffer Object and copy the vertex data to it GLuint vbo; glGenBuffers( 1, &vbo ); float vertices[] = { 1.0f, 1.0f, 1.0f, // Vertex 0 (X, Y, Z) -1.0f, 1.0f, 1.0f, // Vertex 1 (X, Y, Z) -1.0f, -1.0f, 1.0f, // Vertex 2 (X, Y, Z) 1.0f, -1.0f, 1.0f, // Vertex 3 (X, Y, Z) 1.0f, 1.0f, -1.0f, // Vertex 4 (X, Y, Z) -1.0f, 1.0f, -1.0f, // Vertex 5 (X, Y, Z) -1.0f, -1.0f, -1.0f, // Vertex 6 (X, Y, Z) 1.0f, -1.0f, -1.0f // Vertex 7 (X, Y, Z) }; GLuint indices[] = { 0, 1, 1, 2, 2, 3, 3, 0, 4, 5, 5, 6, 6, 7, 7, 4, 0, 4, 1, 5, 2, 6, 3, 7 }; glBindBuffer( GL_ARRAY_BUFFER, vbo ); glBufferData( GL_ARRAY_BUFFER, sizeof( vertices ), vertices, GL_STATIC_DRAW ); //glBindBuffer( GL_ELEMENT_ARRAY_BUFFER, vbo); //glBufferData( GL_ELEMENT_ARRAY_BUFFER, sizeof( indices ), indices, GL_STATIC_DRAW ); // Create and compile the vertex shader GLuint vertexShader = glCreateShader( GL_VERTEX_SHADER ); glShaderSource( vertexShader, 1, &vertexSource, NULL ); glCompileShader( vertexShader ); // Create and compile the fragment shader GLuint fragmentShader = glCreateShader( GL_FRAGMENT_SHADER ); glShaderSource( fragmentShader, 1, &fragmentSource, NULL ); glCompileShader( fragmentShader ); // Link the vertex and fragment shader into a shader program GLuint shaderProgram = glCreateProgram(); glAttachShader( shaderProgram, vertexShader ); glAttachShader( shaderProgram, fragmentShader ); glBindFragDataLocation( shaderProgram, 0, "outColor" ); glLinkProgram (shaderProgram); glUseProgram( shaderProgram); // Specify the layout of the vertex data GLint posAttrib = glGetAttribLocation( shaderProgram, "position" ); glEnableVertexAttribArray( posAttrib ); glVertexAttribPointer( posAttrib, 3, GL_FLOAT, GL_FALSE, 0, 0 ); // Main loop while(glfwGetWindowParam(GLFW_OPENED)) { // Clear the screen to black glClearColor( 0.0f, 0.0f, 0.0f, 1.0f ); glClear( GL_COLOR_BUFFER_BIT ); // Draw lines from 2 vertices glDrawElements(GL_LINES, sizeof(indices), GL_UNSIGNED_INT, indices ); // Swap buffers glfwSwapBuffers(); } // Clean up glDeleteProgram( shaderProgram ); glDeleteShader( fragmentShader ); glDeleteShader( vertexShader ); //glDeleteBuffers( 1, &ebo ); glDeleteBuffers( 1, &vbo ); glDeleteVertexArrays( 1, &vao ); glfwTerminate(); exit( EXIT_SUCCESS ); }

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• Roles / Profiles / Perspectives in NetBeans IDE 7.1

  - by Geertjan

  With a check out of main-silver from yesterday, I'm able to use the brand new "role" attribute in @TopComponent.Registration, as you can see below, in the bit in bold: @ConvertAsProperties(dtd = "-//org.role.demo.ui//Admin//EN", autostore = false) @TopComponent.Description(preferredID = "AdminTopComponent", //iconBase="SET/PATH/TO/ICON/HERE", persistenceType = TopComponent.PERSISTENCE_ALWAYS) @TopComponent.Registration(mode = "editor", openAtStartup = true, role="admin") public final class AdminTopComponent extends TopComponent { And here's a window for general users of the application, with the "role" attribute set to "user": @ConvertAsProperties(dtd = "-//org.role.demo.ui//User//EN", autostore = false) @TopComponent.Description(preferredID = "UserTopComponent", //iconBase="SET/PATH/TO/ICON/HERE", persistenceType = TopComponent.PERSISTENCE_ALWAYS) @TopComponent.Registration(mode = "explorer", openAtStartup = true, role="user") public final class UserTopComponent extends TopComponent { So, I have two windows. One is assigned to the "admin" role, the other to the "user" role. In the "ModuleInstall" class, I add a "WindowSystemListener" and set "user" as the application's role: public class Installer extends ModuleInstall implements WindowSystemListener { @Override public void restored() { WindowManager.getDefault().addWindowSystemListener(this); } @Override public void beforeLoad(WindowSystemEvent event) { WindowManager.getDefault().setRole("user"); WindowManager.getDefault().removeWindowSystemListener(this); } @Override public void afterLoad(WindowSystemEvent event) { } @Override public void beforeSave(WindowSystemEvent event) { } @Override public void afterSave(WindowSystemEvent event) { } } So, when the application starts, the "UserTopComponent" is shown, not the "AdminTopComponent". Next, I have two Actions, for switching between the two roles, as shown below: @ActionID(category = "Window", id = "org.role.demo.ui.SwitchToAdminAction") @ActionRegistration(displayName = "#CTL_SwitchToAdminAction") @ActionReferences({ @ActionReference(path = "Menu/Window", position = 250) }) @Messages("CTL_SwitchToAdminAction=Switch To Admin") public final class SwitchToAdminAction extends AbstractAction { @Override public void actionPerformed(ActionEvent e) { WindowManager.getDefault().setRole("admin"); } @Override public boolean isEnabled() { return !WindowManager.getDefault().getRole().equals("admin"); } } @ActionID(category = "Window", id = "org.role.demo.ui.SwitchToUserAction") @ActionRegistration(displayName = "#CTL_SwitchToUserAction") @ActionReferences({ @ActionReference(path = "Menu/Window", position = 250) }) @Messages("CTL_SwitchToUserAction=Switch To User") public final class SwitchToUserAction extends AbstractAction { @Override public void actionPerformed(ActionEvent e) { WindowManager.getDefault().setRole("user"); } @Override public boolean isEnabled() { return !WindowManager.getDefault().getRole().equals("user"); } } When I select one of the above actions, the role changes, and the other window is shown. I could, of course, add a Login dialog to the "SwitchToAdminAction", so that authentication is required in order to switch to the "admin" role. Now, let's say I am now in the "user" role. So, the "UserTopComponent" shown above is now opened. I decide to also open another window, the Properties window, as below... ...and, when I am in the "admin" role, when the "AdminTopComponent" is open, I decide to also open the Output window, as below... Now, when I switch from one role to the other, the additional window/s I opened will also be opened, together with the explicit members of the currently selected role. And, the main window position and size are also persisted across roles. When I look in the "build" folder of my project in development, I see two different Windows2Local folders, one per role, automatically created by the fact that there is something to be persisted for a particular role, e.g., when a switch to a different role is done: And, with that, we now clearly have roles/profiles/perspectives in NetBeans Platform applications from NetBeans Platform 7.1 onwards.

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• Efficiently separating Read/Compute/Write steps for concurrent processing of entities in Entity/Component systems

  - by TravisG

  Setup I have an entity-component architecture where Entities can have a set of attributes (which are pure data with no behavior) and there exist systems that run the entity logic which act on that data. Essentially, in somewhat pseudo-code: Entity { id; map<id_type, Attribute> attributes; } System { update(); vector<Entity> entities; } A system that just moves along all entities at a constant rate might be MovementSystem extends System { update() { for each entity in entities position = entity.attributes["position"]; position += vec3(1,1,1); } } Essentially, I'm trying to parallelise update() as efficiently as possible. This can be done by running entire systems in parallel, or by giving each update() of one system a couple of components so different threads can execute the update of the same system, but for a different subset of entities registered with that system. Problem In reality, these systems sometimes require that entities interact(/read/write data from/to) each other, sometimes within the same system (e.g. an AI system that reads state from other entities surrounding the current processed entity), but sometimes between different systems that depend on each other (i.e. a movement system that requires data from a system that processes user input). Now, when trying to parallelize the update phases of entity/component systems, the phases in which data (components/attributes) from Entities are read and used to compute something, and the phase where the modified data is written back to entities need to be separated in order to avoid data races. Otherwise the only way (not taking into account just "critical section"ing everything) to avoid them is to serialize parts of the update process that depend on other parts. This seems ugly. To me it would seem more elegant to be able to (ideally) have all processing running in parallel, where a system may read data from all entities as it wishes, but doesn't write modifications to that data back until some later point. The fact that this is even possible is based on the assumption that modification write-backs are usually very small in complexity, and don't require much performance, whereas computations are very expensive (relatively). So the overhead added by a delayed-write phase might be evened out by more efficient updating of entities (by having threads work more % of the time instead of waiting). A concrete example of this might be a system that updates physics. The system needs to both read and write a lot of data to and from entities. Optimally, there would be a system in place where all available threads update a subset of all entities registered with the physics system. In the case of the physics system this isn't trivially possible because of race conditions. So without a workaround, we would have to find other systems to run in parallel (which don't modify the same data as the physics system), other wise the remaining threads are waiting and wasting time. However, that has disadvantages Practically, the L3 cache is pretty much always better utilized when updating a large system with multiple threads, as opposed to multiple systems at once, which all act on different sets of data. Finding and assembling other systems to run in parallel can be extremely time consuming to design well enough to optimize performance. Sometimes, it might even not be possible at all because a system just depends on data that is touched by all other systems. Solution? In my thinking, a possible solution would be a system where reading/updating and writing of data is separated, so that in one expensive phase, systems only read data and compute what they need to compute, and then in a separate, performance-wise cheap, write phase, attributes of entities that needed to be modified are finally written back to the entities. The Question How might such a system be implemented to achieve optimal performance, as well as making programmer life easier? What are the implementation details of such a system and what might have to be changed in the existing EC-architecture to accommodate this solution?

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• Extrapolation breaks collision detection

  - by user22241

  Before applying extrapolation to my sprite's movement, my collision worked perfectly. However, after applying extrapolation to my sprite's movement (to smooth things out), the collision no longer works. This is how things worked before extrapolation: However, after I implement my extrapolation, the collision routine breaks. I am assuming this is because it is acting upon the new coordinate that has been produced by the extrapolation routine (which is situated in my render call ). After I apply my extrapolation How to correct this behaviour? I've tried puting an extra collision check just after extrapolation - this does seem to clear up a lot of the problems but I've ruled this out because putting logic into my rendering is out of the question. I've also tried making a copy of the spritesX position, extrapolating that and drawing using that rather than the original, thus leaving the original intact for the logic to pick up on - this seems a better option, but it still produces some weird effects when colliding with walls. I'm pretty sure this also isn't the correct way to deal with this. I've found a couple of similar questions on here but the answers haven't helped me. This is my extrapolation code: public void onDrawFrame(GL10 gl) { //Set/Re-set loop back to 0 to start counting again loops=0; while(System.currentTimeMillis() > nextGameTick && loops < maxFrameskip){ SceneManager.getInstance().getCurrentScene().updateLogic(); nextGameTick+=skipTicks; timeCorrection += (1000d/ticksPerSecond) % 1; nextGameTick+=timeCorrection; timeCorrection %=1; loops++; tics++; } extrapolation = (float)(System.currentTimeMillis() + skipTicks - nextGameTick) / (float)skipTicks; render(extrapolation); } Applying extrapolation render(float extrapolation){ //This example shows extrapolation for X axis only. Y position (spriteScreenY is assumed to be valid) extrapolatedPosX = spriteGridX+(SpriteXVelocity*dt)*extrapolation; spriteScreenPosX = extrapolationPosX * screenWidth; drawSprite(spriteScreenX, spriteScreenY); } Edit As I mentioned above, I have tried making a copy of the sprite's coordinates specifically to draw with.... this has it's own problems. Firstly, regardless of the copying, when the sprite is moving, it's super-smooth, when it stops, it's wobbling slightly left/right - as it's still extrapolating it's position based on the time. Is this normal behavior and can we 'turn it off' when the sprite stops? I've tried having flags for left / right and only extrapolating if either of these is enabled. I've also tried copying the last and current positions to see if there is any difference. However, as far as collision goes, these don't help. If the user is pressing say, the right button and the sprite is moving right, when it hits a wall, if the user continues to hold the right button down, the sprite will keep animating to the right, while being stopped by the wall (therefore not actually moving), however because the right flag is still set and also because the collision routine is constantly moving the sprite out of the wall, it still appear to the code (not the player) that the sprite is still moving, and therefore extrapolation continues. So what the player would see, is the sprite 'static' (yes, it's animating, but it's not actually moving across the screen), and every now and then it shakes violently as the extrapolation attempts to do it's thing....... Hope this help

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• Animation Trouble with Java Swing Timer - Also, JFrame Will Not Exit_On_Close

  - by forgotton_semicolon

  So, I am using a Java Swing Timer because putting the animation code in a run() method of a Thread subclass caused an insane amount of flickering that is really a terrible experience for any video game player. Can anyone give me any tips on: Why there is no animation... Why the JFrame will not close when it is coded to Exit_On_Close 2 times My code is here: import java.awt.; import java.awt.event.; import javax.swing.*; import java.net.URL; //////////////////////////////////////////////////////////////// TFQ public class TFQ extends JFrame { DrawingsInSpace dis; //========================================================== constructor public TFQ() { dis = new DrawingsInSpace(); JPanel content = new JPanel(); content.setLayout(new FlowLayout()); this.setContentPane(dis); this.setDefaultCloseOperation(EXIT_ON_CLOSE); this.setTitle("Plasma_Orbs_Off_Orion"); this.setSize(500,500); this.pack(); //... Create timer which calls action listener every second.. // Use full package qualification for javax.swing.Timer // to avoid potential conflicts with java.util.Timer. javax.swing.Timer t = new javax.swing.Timer(500, new TimePhaseListener()); t.start(); } /////////////////////////////////////////////// inner class Listener thing class TimePhaseListener implements ActionListener, KeyListener { // counter int total; // loop control boolean Its_a_go = true; //position of our matrix int tf = -400; //sprite directions int Sprite_Direction; final int RIGHT = 1; final int LEFT = 2; //for obstacle Rectangle mega_obstacle = new Rectangle(200, 0, 20, HEIGHT); public void actionPerformed(ActionEvent e) { //... Whenever this is called, repaint the screen dis.repaint(); addKeyListener(this); while (Its_a_go) { try { dis.repaint(); if(Sprite_Direction == RIGHT) { dis.matrix.x += 2; } // end if i think if(Sprite_Direction == LEFT) { dis.matrix.x -= 2; } } catch(Exception ex) { System.out.println(ex); } } // end while i think } // end actionPerformed @Override public void keyPressed(KeyEvent arg0) { // TODO Auto-generated method stub } @Override public void keyReleased(KeyEvent arg0) { // TODO Auto-generated method stub } @Override public void keyTyped(KeyEvent event) { // TODO Auto-generated method stub if (event.getKeyChar()=='f'){ Sprite_Direction = RIGHT; System.out.println("matrix should be animating now "); System.out.println("current matrix position = " + dis.matrix.x); } if (event.getKeyChar()=='d') { Sprite_Direction = LEFT; System.out.println("matrix should be going in reverse"); System.out.println("current matrix position = " + dis.matrix.x); } } } //================================================================= main public static void main(String[] args) { JFrame SafetyPins = new TFQ(); SafetyPins.setVisible(true); SafetyPins.setSize(500,500); SafetyPins.setResizable(true); SafetyPins.setLocationRelativeTo(null); SafetyPins.setDefaultCloseOperation(EXIT_ON_CLOSE); } } class DrawingsInSpace extends JPanel { URL url1_plasma_orbs; URL url2_matrix; Image img1_plasma_orbs; Image img2_matrix; // for the plasma_orbs Rectangle bbb = new Rectangle(0,0, 0, 0); // for the matrix Rectangle matrix = new Rectangle(-400, 60, 430, 200); public DrawingsInSpace() { //load URLs try { url1_plasma_orbs = this.getClass().getResource("plasma_orbs.png"); url2_matrix = this.getClass().getResource("matrix.png"); } catch(Exception e) { System.out.println(e); } // attach the URLs to the images img1_plasma_orbs = Toolkit.getDefaultToolkit().getImage(url1_plasma_orbs); img2_matrix = Toolkit.getDefaultToolkit().getImage(url2_matrix); } public void paintComponent(Graphics g) { super.paintComponent(g); // draw the plasma_orbs g.drawImage(img1_plasma_orbs, bbb.x, bbb.y,this); //draw the matrix g.drawImage(img2_matrix, matrix.x, matrix.y, this); } } // end class enter code here

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• Color Picking Troubles - LWJGL/OpenGL

  - by Tom Johnson

  I'm attempting to check which object the user is hovering over. While everything seems to be just how I'd think it should be, I'm not able to get the correct color due to the second time I draw (without picking colors). Here is my rendering code: public void render() { glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); glLoadIdentity(); camera.applyTranslations(); scene.pick(); glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); glLoadIdentity(); camera.applyTranslations(); scene.render(); } And here is what gets called on each block/tile on "scene.pick()": public void pick() { glColor3ub((byte) pickingColor.x, (byte) pickingColor.y, (byte) pickingColor.z); draw(); glReadBuffer(GL_FRONT); ByteBuffer buffer = BufferUtils.createByteBuffer(4); glReadPixels(Mouse.getX(), Mouse.getY(), 1, 1, GL_RGBA, GL_UNSIGNED_BYTE, buffer); int r = buffer.get(0) & 0xFF; int g = buffer.get(1) & 0xFF; int b = buffer.get(2) & 0xFF; if(r == pickingColor.x && g == pickingColor.y && b == pickingColor.z) { hovered = true; } else { hovered = false; } } I believe the problem is that in the method of each tile/block called by scene.pick(), it is reading the color from the regular drawing state, after that method is called somehow. I believe this because when I remove the "glReadBuffer(GL_FRONT)" line from the pick method, it seems to almost fix it, but then it will also select blocks behind the one you are hovering as it is not only looking at the front. If you have any ideas of what to do, please be sure to reply!/ EDIT: Adding scene.render(), tile.render(), and tile.draw() scene.render: public void render() { for(int x = 0; x < tiles.length; x++) { for(int z = 0; z < tiles.length; z++) { tiles[x][z].render(); } } } tile.render: public void render() { glColor3f(color.x, color.y, color.z); draw(); if(hovered) { glColor3f(1, 1, 1); glPolygonMode(GL_FRONT_AND_BACK, GL_LINE); draw(); glPolygonMode(GL_FRONT_AND_BACK, GL_FILL); } } tile.draw: public void draw() { float x = position.x, y = position.y, z = position.z; //Top glBegin(GL_QUADS); glVertex3f(x, y + size, z); glVertex3f(x + size, y + size, z); glVertex3f(x + size, y + size, z + size); glVertex3f(x, y + size, z + size); glEnd(); //Left glBegin(GL_QUADS); glVertex3f(x, y, z); glVertex3f(x + size, y, z); glVertex3f(x + size, y + size, z); glVertex3f(x, y + size, z); glEnd(); //Right glBegin(GL_QUADS); glVertex3f(x + size, y, z); glVertex3f(x + size, y + size, z); glVertex3f(x + size, y + size, z + size); glVertex3f(x + size, y, z + size); glEnd(); } (The game is like an isometric game. That's why I only draw 3 faces.)

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• Omni-directional light shadow mapping with cubemaps in WebGL

  - by Winged

  First of all I must say, that I have read a lot of posts describing an usage of cubemaps, but I'm still confused about how to use them. My goal is to achieve a simple omni-directional (point) light type shading in my WebGL application. I know that there is a lot more techniques (like using Two-Hemispheres or Camera Space Shadow Mapping) which are way more efficient, but for an educational purpose cubemaps are my primary goal. Till now, I have adapted a simple shadow mapping which works with spotlights (with one exception: I don't know how to cut off the glitchy part beyond the reach of a single shadow map texture): glitchy shadow mapping<<< So for now, this is how I understand the usage of cubemaps in shadow mapping: Setup a framebuffer (in case of cubemaps - 6 framebuffers; 6 instead of 1 because every usage of framebufferTexture2D slows down an execution which is nicely described here <<<) and a texture cubemap. Also in WebGL depth components are not well supported, so I need to render it to RGBA first. this.texture = gl.createTexture(); gl.bindTexture(gl.TEXTURE_CUBE_MAP, this.texture); gl.texParameteri(gl.TEXTURE_CUBE_MAP, gl.TEXTURE_MIN_FILTER, gl.LINEAR); gl.texParameteri(gl.TEXTURE_CUBE_MAP, gl.TEXTURE_MAG_FILTER, gl.LINEAR); for (var face = 0; face < 6; face++) gl.texImage2D(gl.TEXTURE_CUBE_MAP_POSITIVE_X + face, 0, gl.RGBA, this.size, this.size, 0, gl.RGBA, gl.UNSIGNED_BYTE, null); gl.bindTexture(gl.TEXTURE_CUBE_MAP, null); this.framebuffer = []; for (face = 0; face < 6; face++) { this.framebuffer[face] = gl.createFramebuffer(); gl.bindFramebuffer(gl.FRAMEBUFFER, this.framebuffer[face]); gl.framebufferTexture2D(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.TEXTURE_CUBE_MAP_POSITIVE_X + face, this.texture, 0); gl.framebufferRenderbuffer(gl.FRAMEBUFFER, gl.DEPTH_ATTACHMENT, gl.RENDERBUFFER, this.depthbuffer); var e = gl.checkFramebufferStatus(gl.FRAMEBUFFER); // Check for errors if (e !== gl.FRAMEBUFFER_COMPLETE) throw "Cubemap framebuffer object is incomplete: " + e.toString(); } Setup the light and the camera (I'm not sure if should I store all of 6 view matrices and send them to shaders later, or is there a way to do it with just one view matrix). Render the scene 6 times from the light's position, each time in another direction (X, -X, Y, -Y, Z, -Z) for (var face = 0; face < 6; face++) { gl.bindFramebuffer(gl.FRAMEBUFFER, shadow.buffer.framebuffer[face]); gl.viewport(0, 0, shadow.buffer.size, shadow.buffer.size); gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT); camera.lookAt( light.position.add( cubeMapDirections[face] ) ); scene.draw(shadow.program); } In a second pass, calculate the projection a a current vertex using light's projection and view matrix. Now I don't know If should I calculate 6 of them, because of 6 faces of a cubemap. ScaleMatrix pushes the projected vertex into the 0.0 - 1.0 region. vDepthPosition = ScaleMatrix * uPMatrixFromLight * uVMatrixFromLight * vWorldVertex; In a fragment shader calculate the distance between the current vertex and the light position and check if it's deeper then the depth information read from earlier rendered shadow map. I know how to do it with a 2D Texture, but I have no idea how should I use cubemap texture here. I have read that texture lookups into cubemaps are performed by a normal vector instead of a UV coordinate. What vector should I use? Just a normalized vector pointing to the current vertex? For now, my code for this part looks like this (not working yet): float shadow = 1.0; vec3 depth = vDepthPosition.xyz / vDepthPosition.w; depth.z = length(vWorldVertex.xyz - uLightPosition) * linearDepthConstant; float shadowDepth = unpack(textureCube(uDepthMapSampler, vWorldVertex.xyz)); if (depth.z > shadowDepth) shadow = 0.5; Could you give me some hints or examples (preferably in WebGL code) how I should build it?

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• Drawing random smooth lines contained in a square [migrated]

  - by Doug Mercer

  I'm trying to write a matlab function that creates random, smooth trajectories in a square of finite side length. Here is my current attempt at such a procedure: function [] = drawroutes( SideLength, v, t) %DRAWROUTES Summary of this function goes here % Detailed explanation goes here %Some parameters intended to help help keep the particles in the box RandAccel=.01; ConservAccel=0; speedlimit=.1; G=10^(-8); % %Initialize Matrices Ax=zeros(v,10*t); Ay=Ax; vx=Ax; vy=Ax; x=Ax; y=Ax; sx=zeros(v,1); sy=zeros(v,1); % %Define initial position in square x(:,1)=SideLength*.15*ones(v,1)+(SideLength*.7)*rand(v,1); y(:,1)=SideLength*.15*ones(v,1)+(SideLength*.7)*rand(v,1); % for i=2:10*t %Measure minimum particle distance component wise from boundary %for each vehicle BorderGravX=[abs(SideLength*ones(v,1)-x(:,i-1)),abs(x(:,i-1))]'; BorderGravY=[abs(SideLength*ones(v,1)-y(:,i-1)),abs(y(:,i-1))]'; rx=min(BorderGravX)'; ry=min(BorderGravY)'; % %Set the sign of the repulsive force for k=1:v if x(k,i)<.5*SideLength sx(k)=1; else sx(k)=-1; end if y(k,i)<.5*SideLength sy(k)=1; else sy(k)=-1; end end % %Calculate Acceleration w/ random "nudge" and repulive force Ax(:,i)=ConservAccel*Ax(:,i-1)+RandAccel*(rand(v,1)-.5*ones(v,1))+sx*G./rx.^2; Ay(:,i)=ConservAccel*Ay(:,i-1)+RandAccel*(rand(v,1)-.5*ones(v,1))+sy*G./ry.^2; % %Ad hoc method of trying to slow down particles from jumping outside of %feasible region for h=1:v if abs(vx(h,i-1)+Ax(h,i))<speedlimit vx(h,i)=vx(h,i-1)+Ax(h,i); elseif (vx(h,i-1)+Ax(h,i))<-speedlimit vx(h,i)=-speedlimit; else vx(h,i)=speedlimit; end end for h=1:v if abs(vy(h,i-1)+Ay(h,i))<speedlimit vy(h,i)=vy(h,i-1)+Ay(h,i); elseif (vy(h,i-1)+Ay(h,i))<-speedlimit vy(h,i)=-speedlimit; else vy(h,i)=speedlimit; end end % %Update position x(:,i)=x(:,i-1)+(vx(:,i-1)+vx(:,i))/2; y(:,i)=y(:,i-1)+(vy(:,i-1)+vy(:,1))/2; % end %Plot position clf; hold on; axis([-100,SideLength+100,-100,SideLength+100]); cc=hsv(v); for j=1:v plot(x(j,1),y(j,1),'ko') plot(x(j,:),y(j,:),'color',cc(j,:)) end hold off; % end My original plan was to place particles within a square, and move them around by allowing their acceleration in the x and y direction to be governed by a uniformly distributed random variable. To keep the particles within the square, I tried to create a repulsive force that would push the particles away from the boundaries of the square. In practice, the particles tend to leave the desired "feasible" region after a relatively small number of time steps (say, 1000)." I'd love to hear your suggestions on either modifying my existing code or considering the problem from another perspective. When reading the code, please don't feel the need to get hung up on any of the ad hoc parameters at the very beginning of the script. They seem to help, but I don't believe any beside the "G" constant should truly be necessary to make this system work. Here is an example of the current output: Many of the vehicles have found their way outside of the desired square region, [0,400] X [0,400].

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• 100,000 complex structures that are accessed frequently by 100,000 users

  - by Saad

  If you are required to store 100,000 complex structures that are accessed frequently by 100,000 users, which of the following solutions would you use and why? Memcached, In-code python objects, Redis, or a relational database (MySQL). With the little knowledge that I have I think that memcached and In-code python object will not store permanent persistent data. so they don't qualify as the right answer for such a problem. And for complex data structures its best to use Redis. Please correct me if I am wrong.

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• User generated articles, how to do meta description?

  - by Tom Gullen

  If users submit a lot of good quality articles on the site, what is the best way to approach the meta description tag? I see two options: Have a description box and rely on them to fill it sensibly and in a good quality way Just exclude the meta description Method 1 is bad initially, but I'm willing to put time in going through and editing/checking all of them on a permanent basis. Method 2 is employed by the stack exchange site, and lets the search bots extract the best part of the page in the SERP. Thoughts? Ideas? I'm thinking a badly formed description tag is more damaging than not having one at all at the end of the day. I don't expect content to ever become unwieldy and too much to manage.

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• Permanently redirect your asp.net pages in ASP.Net 4.0

  - by nikolaosk

  Hello all, In this post, I would like to talk about a new method of the Response object that comes with ASP.Net 4.0. The name of the method is RedirectPermanent . Let's talk a bit about 301 redirection and permanent redirection.301 redirect is the most efficient and Search Engine Friendly method for webpage redirection. Let's imagine that we have this scenario. This is a very common scenario. We have redesigned and move folders to some pages that have high search engine rankings. We do not want to...(read more)

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• Country selection, when country is not listed

  - by David Balažic

  While this might not 100% match the intent of this site, it was the closest match from Stackexchange sites. So, if a web site (the "entrance" page) offers a choice (a list) of countries, with the text "Chose your country", but the users country is not listed, what should he do? One example is http://www.samsung.com/countryselection.do Addition: I ask this standing in the users position. I encounter a web site and it gives me the above page. What to do? Another issue: What is "my" country? My current location? My permanent residence? The country of my citizenship? Something else?

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• Will TSQL become useless because of new ORMs? [closed]

  - by Saeed Neamati

  By introducing LINQ to SQL, I found myself and my .NET developer colleagues gradually moving from TSQL to C# to create queries on the database. Entity Framework made that shift almost permanent. Now it's nearly 2 years that I use LINQ to SQL and LINQ to Entities and haven't used TSQL that much. Yesterday, a colleague encountered a problem (he had to create a SP) and we went to help him. But we all found that our TSQL knowledge was diminished for sure, and a simple SP that seemed trivial to us 2 or 3 years ago, was a challenge to be solved yesterday. Thus it came to my mind that while TSQL's life is attached to SQL Server, and logically as long as SQL Server lives and doesn't change it's SQL language, TSQL would also live, practically it might die, and soon very few people might know it. Am I right? Do existence of ORMs like Entity Framework threaten TSQL's life and usability?

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• Tab Sweep - More OSGi, Coherence, Oracle Java moves, JMS 2.0 and more

  - by alexismp

  Recent Tips and News on Java, Java EE 6, GlassFish & more : • Why I will use Java EE (JEE, and not J2EE) instead of Spring in new Enterprise Java Projects (Kai) • What is Happening vs. What is Interesting (Geertjan) • Oracle Coherence & Oracle Service Bus: REST API Integration (Nino) • Oracle's Top 10 Java Moves of 2011 (eWeek) • JEP 122: Remove the Permanent Generation (OpenJDK.org) • JEE6 – Glassfish 3.1, Clustering & Failover (Xebia.fr) • Testing LAZY mechanism in EJB 3 (e-blog-java) • Discoing with Vorpal (Chuk) • Devoxx : les évolutions de JMS 2.0 (Ippon.fr) • More OSGi... (Jarda) • Practical Migration to Java 7 - Small Codeexamples (FOSSLC) • Coherence Part III : Filtres (Zenika.com)

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• How to make "xset s off" survive a reboot (12.04)

  - by matteo

  On an almost-fresh install of Ubuntu 12.04, after disabling screen turning off, screen lock, and suspension on inactivity from all the (two) places one can find under Ubuntu's System Settings, the screen still turns black after some minutes of inactivity. I can't tell for sure whether it only becomes blank/black or turns off. I've uninstalled gnome-screensaver, which didn't change anything. Of the several answers I found out there (most of which I didn't try because they were either unclear or reported to not work for everybody), I tried one that DID work: sudo xset s off after which I left the computer unattended for hours and the screen never turned black, so it definitely worked. HOWEVER it does not survive a reboot. After reboot, screen starts turning black again after N minutes of inactivity. Given that "xset s off" does work until reboot, how do I make that setting permanent? I guess I could create a script that runs at startup issuing that command, but I think that would be a horrible hack and there should be a cleaner way to accomplish this.

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• Can Ubuntu launcher damage my LCD screen pixels?

  - by DUKE

  There appears something like a scar (damaged or dead pixels) on my LCD screen, where Ubuntu launcher positions. The scar exactly fitting Ubuntu launcher edges and icons. It seems a permanent scar and it stays even if I load other operating systems. Can this damage be a cause of Ubuntu launcher? I know this is a stupid question, but I decided to ask here because this is exactly fitting Ubuntu launcher edges and icons. I am using Ubuntu 12.04 LTS and Samsung LCD. My system details as follows:

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• What is the best solution for document archiving?

  - by Anders Wallenquist

  I'm looking for a utility that helps me (and my colleagues) to archive documents in a systematic manner (Like Zeitgeist but permanent). The utility have to clean-out old document from desktops and store them on a server (as automatic as possible and consistent) maybe from just a few locations (Document directory) Documents shall be stored on cheap large media for many years to come - hard disk and file system maybe? Easy to maintain and manage for a small organization. Documents have to be easy to find and restore One systematic manner could be a directory-structure by year, month, user or user, year, month. Its a plus if documents could be linked to a project, if documents could be search-able and if document could also be mail, IM-discussions not only OpenOffice traditional documents. Any ideas?

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• Firefox ignore GTK theme for localhost stuff

  - by Mario De Schaepmeester

  I know this is pretty much a duplicate of How can one make firefox ignore my GTK theme entirely?, but the answers on that one are no permanent solution. It works by launching firefox from the terminal. I would like to know a solution that works for every instance of firefox no matter how it was created. There is the possibility to edit the userContent.css file, but the settings you make randomly do not apply to some sites or in some situations, strangely, even with the !important added... I have a dark GTK theme and this results in some textboxes having a black background with black text with a userContent.css that has input, textarea { color: black !important; background-color: white !important; } Update I changed a setting in about:config from true to false, namely browser.display.use_system_colors. Everything appears normal and well now, for one exception: everything that runs on localhost. This includes PHPMyAdmin and a website I am making. I would like to know if there is a solution to this.

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• Adding user to chroot environment

  - by Neo

  I've created a chroot system in my Ubuntu using schroot and debrootstrap, based on minimal ubuntu. However whenever I can't seem to add a new user into this chroot environment. Here is what happens. I enter schroot as root and add a new user 'Bob'.(Tried both adduser and useradd commands) The username 'Bob' lists up in /etc/passwd file and I can 'su' into the user 'Bob'. So far so good. When I log out of schroot, and re-enter schroot, the user 'Bob' has vanished!! There is no mention of Bob in /etc/passwd either. How do I make the new user permanent?

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• Organization &amp; Architecture UNISA Studies &ndash; Chap 5

  - by MarkPearl

  Learning Outcomes Describe the operation of a memory cell Explain the difference between DRAM and SRAM Discuss the different types of ROM Explain the concepts of a hard failure and a soft error respectively Describe SDRAM organization Semiconductor Main Memory The two traditional forms of RAM used in computers are DRAM and SRAM DRAM (Dynamic RAM) Divided into two technologies… Dynamic Static Dynamic RAM is made with cells that store data as charge on capacitors. The presence or absence of charge in a capacitor is interpreted as a binary 1 or 0. Because capacitors have natural tendency to discharge, dynamic RAM requires periodic charge refreshing to maintain data storage. The term dynamic refers to the tendency of the stored charge to leak away, even with power continuously applied. Although the DRAM cell is used to store a single bit (0 or 1), it is essentially an analogue device. The capacitor can store any charge value within a range, a threshold value determines whether the charge is interpreted as a 1 or 0. SRAM (Static RAM) SRAM is a digital device that uses the same logic elements used in the processor. In SRAM, binary values are stored using traditional flip flop logic configurations. SRAM will hold its data as along as power is supplied to it. Unlike DRAM, no refresh is required to retain data. SRAM vs. DRAM DRAM is simpler and smaller than SRAM. Thus it is more dense and less expensive than SRAM. The cost of the refreshing circuitry for DRAM needs to be considered, but if the machine requires a large amount of memory, DRAM turns out to be cheaper than SRAM. SRAMS are somewhat faster than DRAM, thus SRAM is generally used for cache memory and DRAM is used for main memory. Types of ROM Read Only Memory (ROM) contains a permanent pattern of data that cannot be changed. ROM is non volatile meaning no power source is required to maintain the bit values in memory. While it is possible to read a ROM, it is not possible to write new data into it. An important application of ROM is microprogramming, other applications include library subroutines for frequently wanted functions, System programs, Function tables. A ROM is created like any other integrated circuit chip, with the data actually wired into the chip as part of the fabrication process. To reduce costs of fabrication, we have PROMS. PROMS are… Written only once Non-volatile Written after fabrication Another variation of ROM is the read-mostly memory, which is useful for applications in which read operations are far more frequent than write operations, but for which non volatile storage is required. There are three common forms of read-mostly memory, namely… EPROM EEPROM Flash memory Error Correction Semiconductor memory is subject to errors, which can be classed into two categories… Hard failure – Permanent physical defect so that the memory cell or cells cannot reliably store data Soft failure – Random error that alters the contents of one or more memory cells without damaging the memory (common cause includes power supply issues, etc.) Most modern main memory systems include logic for both detecting and correcting errors. Error detection works as follows… When data is to be read into memory, a calculation is performed on the data to produce a code Both the code and the data are stored When the previously stored word is read out, the code is used to detect and possibly correct errors The error checking provides one of 3 possible results… No errors are detected – the fetched data bits are sent out An error is detected, and it is possible to correct the error. The data bits plus error correction bits are fed into a corrector, which produces a corrected set of bits to be sent out An error is detected, but it is not possible to correct it. This condition is reported Hamming Code See wiki for detailed explanation. We will probably need to know how to do a hemming code – refer to the textbook (pg. 188 – 189) Advanced DRAM organization One of the most critical system bottlenecks when using high-performance processors is the interface to main memory. This interface is the most important pathway in the entire computer system. The basic building block of main memory remains the DRAM chip. In recent years a number of enhancements to the basic DRAM architecture have been explored, and some of these are now on the market including… SDRAM (Synchronous DRAM) DDR-DRAM RDRAM SDRAM (Synchronous DRAM) SDRAM exchanges data with the processor synchronized to an external clock signal and running at the full speed of the processor/memory bus without imposing wait states. SDRAM employs a burst mode to eliminate the address setup time and row and column line precharge time after the first access In burst mode a series of data bits can be clocked out rapidly after the first bit has been accessed SDRAM has a multiple bank internal architecture that improves opportunities for on chip parallelism SDRAM performs best when it is transferring large blocks of data serially There is now an enhanced version of SDRAM known as double data rate SDRAM or DDR-SDRAM that overcomes the once-per-cycle limitation of SDRAM

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• cPanel email doesn't seem to work - error 550?

  - by Megh

  I am fairly new to the web hosting game, so bear with me :) Recently set up a VPS with cPanel and WHM. Everything is going well so far, I've created a user domain and transferred my website there, managed a couple of databases with phpmyadmin, everything was going great until I started messing around with email. I made an email account [email protected] through cPanel, although when I try and email this address I get the following error: Technical details of permanent failure: Google tried to deliver your message, but it was rejected by the recipient domain. We recommend contacting the other email provider for further information about the cause of this error. The error that the other server returned was: 550 550 Unknown user (state 13) Quite unsure of what to do next, in all honesty.

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• SEO Friendly URL for search keywords

  - by Kyojimaru

  I have a website where you can search for a brands, item, and content inside my web. It was designed with tab for each search type, but I want to make the url when changing the tab user friendly and good for SEO. Is it better to have a url for search result like this www.example.com/search/{search_keyword}/{tab} or www.example.com/search/{search_keyword}?tab={tab} or www.example.com/search/?search={search_keyword}&tab={tab} where {search_keyword} is the keyword that user input, and {tab} is either brands / item / content, because when I look at facebook, stackoverflow, and some other website, they use query string for their search keyword Edit My past url is only www.example.com/search/{search_keyword}, and I just added the tab design recently. Consider that I should go with option 1 from the above option, should I make www.example.com/search/{search_keyword} the default for 1 of the 3 tab, and make the other 2 tab with www.example.com/search/{search_keyword}/{tab} to retain the score for the page, or should I make all the tab url with www.example.com/search/{search_keyword}/{tab} and use a permanent redirect from www.example.com/search/{search_keyword} to one of the url tab

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• Screen problems

  - by Erick

  I struggled a lot in order to install Ubuntu because of a problem with the video drivers caused by when installing the driver and after turning it on it just appears a black screen, which worked for me was to use the terminal with sudo setpci -s 00:02.0 F4.B=0 and the screen starts, but after rebooting the changes won't remain and I have to run that command again. My question is: How can I make the changes permanent and not to be in need to execute that command always when I shut it down? Original Question in Spanish: Problemas con pantalla He batallado mucho al instalar ubuntu por el problema con el controlador de video ya que al instalarlo al encenderla aparece solo una pantalla negra lo que me funciono fue usar desde consola sudo setpci -s 00:02.0 F4.B=0 enciende la pantalla pero al reiniciarla los cambios no se quedan guardados y tengo que volver a ejecutar ese comando mi pregunta es ¿como hacerle para que los cambios queden igual y no tener que estar ejecutando eso siempre que la apago?

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• How to prevent WLAN connection from dropping permanently on a Fritz USB WLAN N stick?

  - by Chris

  I have a desktop with a Fritz USB WLAN N stick and tried Ubuntu 12.04. Installation went fine and WLAN is working. However, connection drops permanent. Reconnecting manually fixes it but after a few minutes it drops again. It's connected to a Vodafone 802 box with WLAN N fix set. It seems that it works when I switch off N mode. But I need to test. Can someone confirm this issue or is there another solution? I have another machine with 12.04 (HP 625 laptop) running where connection is stable.

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