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• OpenGl texture mapping blocking colours on FreeType?

  - by Dororo

  I'm using FreeType in order to allow fonts to be used in OpenGL. However, I'm having a problem where I cannot change the font colour whenever I do texture mapping. No matter what I select using glColor3f it will just come out white. The texture works fine. glClear(GL_COLOR_BUFFER_BIT); glLoadIdentity(); glColor3f(0.5,0.0,0.5); glPushMatrix(); glEnable(GL_BLEND); glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA); glEnable(GL_TEXTURE_2D); glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_REPLACE); glBindTexture(GL_TEXTURE_2D, texName); glBegin(GL_POLYGON); glTexCoord2f(0,1); glVertex2f(-16,-16); glTexCoord2f(0,0); glVertex2f(-16,16); glTexCoord2f(1,0); glVertex2f(16,16); glTexCoord2f(1,1); glVertex2f(16,-16); glEnd(); glDisable(GL_TEXTURE_2D); glDisable(GL_BLEND); glPopMatrix(); glColor3f(1,0,0); print(our_font, -300+screenWidth/2.0, screenHeight/2.0, "fifty two - %7.2f", spin); This is the problem code, I can confirm that drawing a polygon beneath this code will indeed make it red. The text is not changing to red though which it should; if you remove the texture mapping above it will turn red again, I can only think it is a problem with enabling and disabling and I've forgotten to do something...?

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• Qt 5.3 OpenGL - vertex buffer object drawing using the core profile

  - by user3700881

  Im using Qt 5.3 to create a QWindow to do some basic rendering stuff. The QWindow is declared like this: class OpenGLWindow : public QWindow, protected QOpenGLFunctions_3_3_Core { Q_OBJECT ... } It is initialized in the constructor: OpenGLWindow::OpenGLWindow(QWindow *parent) : QWindow(parent) { QSurfaceFormat format; format.setVersion(3,3); format.setProfile(QSurfaceFormat::CoreProfile); this->setSurfaceType(OpenGLSurface); this->setFormat(format); this->create(); _context = new QOpenGLContext; _context->setFormat(format); _context->create(); _context->makeCurrent(this); this->initializeOpenGLFunctions(); ... } And that's the rendering code: void OpenGLWindow::render() { if(!isExposed()) return; _context->makeCurrent(this); glClear(GL_COLOR_BUFFER_BIT); glUseProgram(_shaderProgram); glBindBuffer(GL_ARRAY_BUFFER, _positionBufferObject); glEnableVertexAttribArray(0); glVertexAttribPointer(0, 4, GL_FLOAT, GL_FALSE, 0, 0); glDrawArrays(GL_TRIANGLES, 0, 3); glDisableVertexAttribArray(0); glUseProgram(0); _context->swapBuffers(this); } I am trying to draw a simple triangle using a vertex and fragment shader. The problem is that the triangle is not showing up when the core profile is set. Only when I set the OpenGL version to 2.0 or when I use the compatibility profile, it shows up. From my point of view that doesn't make any sense because I am not using fixed functionality at all. What am I missing?

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• OpenGL depth buffer on Android

  - by kayahr

  I'm currently learning OpenGL ES programming on Android (2.1). I started with the obligatory rotating cube. It's rotating fine but I can't get the depth buffer to work. The polygons are always displayed in the order the GL commands render them. I do this during initialization of GL: gl.glClearColor(.5f, .5f, .5f, 1); gl.glShadeModel(GL10.GL_SMOOTH); gl.glClearDepthf(1f); gl.glEnable(GL10.GL_DEPTH_TEST); gl.glDepthFunc(GL10.GL_LEQUAL); gl.glHint(GL10.GL_PERSPECTIVE_CORRECTION_HINT, GL10.GL_NICEST); On surface-change I do this: gl.glViewport(0, 0, width, height); gl.glMatrixMode(GL10.GL_PROJECTION); gl.glLoadIdentity(); GLU.gluPerspective(gl, 45.0f, (float) width / (float) height, 0.1f, 100f); When I enable backface culling then everything looks correct. But backface culling is only a speed-optimization so it should also work with only the depth buffer or not? So what is missing here?

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• opengl color quadrangle

  - by Tyzak

  hello i try out opengl. i have a programm that creates a black border an white corner (quadrangle). now i want to make the corner of the quadrangle in an different color. i don't know where exactly to write the code, and i don't know much a but color4f, i searcherd on google, but didn't get it. (is there a good description somewhere?) #include <iostream> #include <GL/freeglut.h> void Init() { glColor4f(100,0,0,0); } void RenderScene() //Zeichenfunktion { glLoadIdentity (); glBegin( GL_POLYGON ); glVertex3f( -0.5, -0.5, -0.5 ); glVertex3f( 0.5, -0.5, -0.5 ); glVertex3f( 0.5, 0.5, -0.5 ); glVertex3f( -0.5, 0.5, -0.5 ); glEnd(); glFlush(); } void Reshape(int width,int height) { } void Animate (int value) { std::cout << "value=" << value << std::endl; glutPostRedisplay(); glutTimerFunc(100, Animate, ++value); } int main(int argc, char **argv) { glutInit( &argc, argv ); // GLUT initialisieren glutInitDisplayMode( GLUT_RGB ); // Fenster-Konfiguration glutInitWindowSize( 600, 600 ); glutCreateWindow( "inkrement screen; visual screen" ); // Fenster-Erzeugung glutDisplayFunc( RenderScene ); // Zeichenfunktion bekannt machen glutReshapeFunc( Reshape ); glutTimerFunc( 10, Animate, 0); Init(); glutMainLoop(); return 0; }

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• OpenGL bitmap text fails after drawing polygon

  - by kaykun

  Hi, I'm using Win32 and OpenGL to to draw text onto a window. I'm using the bitmap font method, with wglUseFontBitmaps. Here is my main rendering function: glClear(GL_COLOR_BUFFER_BIT); glPushMatrix(); glColor3f(1.0f, 0.0f, 1.0f); glBegin(GL_QUADS); glVertex2f(0.0f, 0.0f); glVertex2f(128.0f, 0.0f); glVertex2f(128.0f, 128.0f); glVertex2f(0.0f, 128.0f); glEnd(); glPopMatrix(); glPushMatrix(); glColor3f(1.0f, 1.0f, 1.0f); glRasterPos2i(200, 200); glListBase(fontList); glCallLists(5, GL_UNSIGNED_BYTE, "Test."); glPopMatrix(); SwapBuffers(hDC); As you can see it's very simple and the only thing that it's supposed to do is draw a quadrilateral and draw the text "Test.". But the problem is that drawing a polygon seems to mess up any text operations I try to do after it. If I place the text drawing functions before the polygon, both the text and the polygon draw fine. Is there something I'm missing here? Any help is appreciated.

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• How to setup OpenGL camera for a racing game

  - by vian

  I need the view to show the road polygon (a rectangle 3.f * 100.f) with a vanishing point for a road being at 3/4 height of the viewport and the nearest road edge as a viewport's bottom side. See Crazy Taxi game for an example of what I wish to do. I'm using iPhone SDK 3.1.2 default OpenGL ES project template. I setup the projection matrix as follows: glMatrixMode(GL_PROJECTION); glLoadIdentity(); glFrustumf(-2.25f, 2.25f, -1.5f, 1.5f, 0.1f, 1000.0f); Then I use glRotatef to adjust for landscape mode and setup camera. glMatrixMode(GL_MODELVIEW); glLoadIdentity(); glRotatef(-90, 0.0f, 0.0f, 1.0f); const float cameraAngle = 45.0f * M_PI / 180.0f; gluLookAt(0.0f, 2.0f, 0.0f, 0.0f, 0.0f, 100.0f, 0.0f, cos(cameraAngle), sin(cameraAngle)); My road polygon triangle strip is like this: static const GLfloat roadVertices[] = { -1.5f, 0.0f, 0.0f, 1.5f, 0.0f, 0.0f, -1.5f, 0.0f, 100.0f, 1.5f, 0.0f, 100.0f, }; And I can't seem to find the right parameters for gluLookAt. My vanishing point is always at the center of the screen.

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• Orthogonal projection and texture coordinates in opengl

  - by knuck

  I'm writing a 2D game in Opengl. I already set up the orthogonal projection so I can easily know where a quad will end up on screen. The problem is, I also want to be able to map pixels directly to texture coords, so I also applied an orthogonal transformation (using gluOrtho2d) to the texture. Now I can map pixels directly using integers and glTexCoord2i. The thing is, after googling/reading/asking, I found out no one really knows (apparently) the behavior of glTexCoord2i, but it works just fine the way I'm using. Some sample test code I wrote follows: glBegin(GL_QUADS); glTexCoord2i(16,0); glVertex2f(X, Y); glTexCoord2i(16,16); glVertex2f(X, Y+32); glTexCoord2i(32, 16); glVertex2f(X+32, Y+32); glTexCoord2i(32, 0); glVertex2f(X+32, Y); glEnd(); So, is there any problem with what I'm doing, or is what I'm doing correct?

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• OpenGL equivalent of GDI's HatchBrush or PatternBrush?

  - by Ptah- Opener of the Mouth

  I have a VB6 application (please don't laugh) which does a lot of drawing via BitBlt and the standard VB6 drawing functions. I am running up against performance issues (yes, I do the regular tricks like drawing to memory). So, I decided to investigate other ways of drawing, and have come upon OpenGL. I've been doing some experimenting, and it seems straightforward to do most of what I want; the application mostly only uses very simple drawing -- relatively large 2D rectangles of solid colors and such -- but I haven't been able to find an equivalent to something like a HatchBrush or PatternBrush. More specifically, I want to be able to specify a small monochrome pixel pattern, choose a color, and whenever I draw a polygon (or whatever), instead of it being solid, have it automatically tiled with that pattern, not translated or rotated or skewed or stretched, with the "on" bits of the pattern showing up in the specified color, and the "off" bits of the pattern left displaying whatever had been drawn under the area that I am now drawing on. Obviously I could do all the calculations myself. That is, instead of drawing as a polygon which will somehow automatically be tiled for me, I could calculate all of the lines or pixels or whatever that actually need to be drawn, then draw them as lines or pixels or whatever. But is there an easier way? Like in GDI, where you just say "draw this polygon using this brush"? I am guessing that "textures" might be able to accomplish what I want, but it's not clear to me (I'm totally new to this and the documentation I've found is not entirely obvious); it seems like textures might skew or translate or stretch the pattern, based upon the vertices of the polygon? Whereas I want the pattern tiled. Is there a way to do this, or something like it, other than brute force calculation of exactly the pixels/lines/whatever that need to be drawn? Thanks in advance for any help.

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• OpenGL pixels drawn with each horizontal pair swapped

  - by Tim Kane

  I'm somewhat new to OpenGL though I'm fairly sure my problem lies in the pixel format being used, or how my texture is being generated... I'm drawing a texture onto a flat 2D quad using a 16bit RGB5_A1 pixel format, though I don't make use of any alpha at this stage. The problem I'm having is that each pair of horizontal pixel values have been swapped. That is... if the pixels positions should be in this order (assume 8x2 image) 0 1 2 3 4 5 6 7 they are instead drawn as 1 0 3 2 5 4 7 6 Or, more clearly from this image (below). Left is what I get... Right is what I should get. . The question is... How have I ended up with this? Is there something wrong with the pixel format? Unlikely since the colours all appear correct, and I would expect all kinds of nasty if it were down to endian-ness. Suggestions greatly appreciated. Update: Turns out the problem was in my source renderer. Interestingly, I've avoided the problem entirely by using 32-bit textures (haven't tried 24-bit at this point).

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• Textures in Opengl ES 2 not working properly

  - by Adl

  Hi! I'm working with Opengl ES 2 on iphone and right now I am trying to get my textures working on my objects. I'm using .obj files and all the data in them are correct. I have written a parser myself to retrieve all data, I convert it to static arrays in C. I discard the material properties for now, only getting the image path from the .mtl files manually. I have an object with 336 triangles, making this non-trivial to observe, with appertaining vertices, vertex faces and texture coordinates (u,v). Passing all data into the shaders, the resulting image is this: http://img530.imageshack.us/img530/9637/pic1io.png http://img404.imageshack.us/img404/7358/pic2pg.png But it should look like this (Displaying it in an object viewer). Please ignore the material properties. http://img16.imageshack.us/img16/1401/pic3cq.png Using this image as a texture: http://img217.imageshack.us/img217/1300/shirtdiffuse.png I'm thinking it might have to do with texture coordinate faces ? It is defined in my .obj file, and I'm not using them at all. In books and tutorials I have not found anything concerning this. Regards Niclas

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• Opengl: Problem with masking

  - by Shaza

  Hey all, I'm working on creating a hole in a wall using masking in opengl, my code is quit simple like this, //Draw the mask glEnable(GL_BLEND); glBlendFunc(GL_DST_COLOR,GL_ZERO); glBindTexture(GL_TEXTURE_2D, texture[3]); glBegin(GL_QUADS); glTexCoord2d(0,0); glVertex3f(-20,40,-20); glTexCoord2d(0,1);glVertex3f(-20,40,40); glTexCoord2d(1,1);glVertex3f(20,40,40); glTexCoord2d(1,0);glVertex3f(20,40,-20); glEnd(); //Draw the Texture glBlendFunc(GL_ONE, GL_ONE); glBindTexture(GL_TEXTURE_2D, texture[2]); glBegin(GL_QUADS); glTexCoord2d(0,0); glVertex3f(-20,40,-20); glTexCoord2d(0,1);glVertex3f(-20,40,40); glTexCoord2d(1,1);glVertex3f(20,40,40); glTexCoord2d(1,0);glVertex3f(20,40,-20); glEnd(); The problem is, I got the hole in the wall correctly but it's semi transparent, I'm getting like black shade over it, also I can see through it. Here's a photo for what I'm getting: any suggestions?

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• How to run OpenGL code with out compiling?

  - by Ole Jak

  So I have some openGL code (such code for example) /* FUNCTION: YCamera :: CalculateWorldCoordinates ARGUMENTS: x mouse x coordinate y mouse y coordinate vec where to store coordinates RETURN: n/a DESCRIPTION: Convert mouse coordinates into world coordinates */ void YCamera :: CalculateWorldCoordinates(float x, float y, YVector3 *vec) { // START GLint viewport[4]; GLdouble mvmatrix[16], projmatrix[16]; GLint real_y; GLdouble mx, my, mz; glGetIntegerv(GL_VIEWPORT, viewport); glGetDoublev(GL_MODELVIEW_MATRIX, mvmatrix); glGetDoublev(GL_PROJECTION_MATRIX, projmatrix); real_y = viewport[3] - (GLint) y - 1; // viewport[3] is height of window in pixels gluUnProject((GLdouble) x, (GLdouble) real_y, 1.0, mvmatrix, projmatrix, viewport, &mx, &my, &mz); /* 'mouse' is the point where mouse projection reaches FAR_PLANE. World coordinates is intersection of line(camera->mouse) with plane(z=0) (see LaMothe 306) Equation of line in 3D: (x-x0)/a = (y-y0)/b = (z-z0)/c Intersection of line with plane: z = 0 x-x0 = a(z-z0)/c <=> x = x0+a(0-z0)/c <=> x = x0 -a*z0/c y = y0 - b*z0/c */ double lx = fPosition.x - mx; double ly = fPosition.y - my; double lz = fPosition.z - mz; double sum = lx*lx + ly*ly + lz*lz; double normal = sqrt(sum); double z0_c = fPosition.z / (lz/normal); vec->x = (float) (fPosition.x - (lx/normal)*z0_c); vec->y = (float) (fPosition.y - (ly/normal)*z0_c); vec->z = 0.0f; } I want to run It but with out precompiling. Is there any way to do such thing

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• Glitch when moving camera in OpenGL

  - by CG

  I am writing a tile-based game engine for the iPhone and it works in general apart from the following glitch. Basically, the camera will always keep the player in the centre of the screen, and it moves to follow the player correctly and draws everything correctly when stationary. However whilst the player is moving, the tiles of the surface the player is walking on glitch as shown: Compared to the stationary (correct): Does anyone have any idea why this could be? Thanks for the responses so far. Floating point error was my first thought also and I tried slightly increasing the size of the tiles but this did not help. Changing glClearColor to red still leaves black gaps so maybe it isn't floating point error. Since the tiles in general will use different textures, I don't know if vertex arrays can be used (I always thought that the same texture had to be applied to everything in the array, correct me if I'm wrong), and I don't think VBO is available in OpenGL ES. Setting the filtering to nearest neighbour improved things but the glitch still happens every ten frames or so, and the pixelly result means that this solution is not viable anyway. The main difference between what I'm doing now and what I've done in the past is that this time I am moving the camera rather than the stationary objects in the world (i.e. the tiles, the player is still being moved). The code I'm using to move the camera is: void Camera::CentreAtPoint( GLfloat x, GLfloat y ) { glMatrixMode(GL_PROJECTION); glLoadIdentity(); glOrthof(x - size.x / 2.0f, x + size.x / 2.0f, y + size.y / 2.0f, y - size.y / 2.0f, 0.01f, 5.0f); glMatrixMode(GL_MODELVIEW); } Is there a problem with doing things this way and if so is there a solution?

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• returning opengl display callback in D

  - by Max

  I've written a simple hello world opengl program in D, using the converted gl headers here. My code so far: import std.string; import c.gl.glut; Display_callback display() { return Display_callback // line 7 { return; // just display a blank window }; } // line 10 void main(string[] args) { glutInit(args.length, args); glutInitDisplayMode(GLUT_RGB | GLUT_DEPTH | GLUT_DOUBLE); glutInitWindowSize(800,600); glutCreateWindow("Hello World"); glutDisplayFunc(display); glutMainLoop(); } My problem is with the display() function. glutDisplayFunc() expects a function that returns a Display_callback, which is typedef'd as typedef GLvoid function() Display_callback;. When I try to compile, dmd says line 7: found '{' when expecting ';' following return statement line 10: unrecognized declaration How do I properly return the Display_callback here? Also, how do I change D strings and string literals into char*? My calls to glutInit and glutCreateWindow don't like the D strings they're getting. Thanks for your help.

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• android opengl es texture mapping into polygons

  - by kamil

  I wrote opengl es code for android to map textures on a square but i want to draw texture on polygons. When user moved the image, texture will be mapped on polygons have more vertexes. I tried the arrays combination below for pentagon but i could not find the correct triangle combination in indices array. public float vertices[] = { // -1.0f, 1.0f, 0.0f, //Top Left // -1.0f, -1.0f, 0.0f, //Bottom Left // 1.0f, -1.0f, 0.0f, //Bottom Right // 1.0f, 1.0f, 0.0f //Top Right -1.0f, 1.0f, 0.0f, //Top Left -1.0f, -1.0f, 0.0f, //Bottom Left 1.0f, -1.0f, 0.0f, //Bottom Right 1.0f, 1.0f, 0.0f, //Top Right 0.4f, 1.4f, 0.0f }; /** Our texture pointer */ private int[] textures = new int[1]; /** The initial texture coordinates (u, v) */ private float texture[] = { //Mapping coordinates for the vertices // 1.0f, 0.0f, // 1.0f, 1.0f, // 0.0f, 1.0f, // 0.0f, 0.0f, // 0.0f, 1.0f, // 0.0f, 0.0f, // 1.0f, 0.0f, // 1.0f, 1.0f, 0.0f, 0.0f, 0.0f, 1.0f, 1.0f, 1.0f, 1.0f, 0.0f, 1.0f, 0.7f, }; /** The initial indices definition */ private byte indices[] = { //2 triangles // 0,1,2, 2,3,0, 0,1,2, 2,3,4, 3,4,0, //triangles for five vertexes }; i draw with the code below gl.glDrawElements(GL10.GL_TRIANGLES, indices.length, GL10.GL_UNSIGNED_BYTE, indexBuffer);

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• Cleaning up when exiting an OpenGL app

  - by Daniel

  This might be a dumb question but I've spent some time asking Google and haven't been able to find anything. I have an an OSX OpenGL app I'm trying to modify. When I create the app a whole bunch of initialisation functions are called -- including methods where I can specify my own mouse and keyboard handlers etc. For example: glutInit(&argc, argv); glutInitDisplayMode(GLUT_DEPTH | GLUT_DOUBLE | GLUT_RGBA); glutInitWindowPosition(100, 100); glutInitWindowSize(700, 700); glutCreateWindow("Map Abstraction"); glutReshapeFunc(resizeWindow); glutDisplayFunc(renderScene); glutIdleFunc(renderScene); glutMouseFunc(mousePressedButton); glutMotionFunc(mouseMovedButton); glutKeyboardFunc(keyPressed); At some point I pass control to glutMainLoop and my application runs. In the process of running I create a whole bunch of objects. I'd like to clean these up. Is there any way I can tell GLUT to call a cleanup method before it quits?

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• Android opengl releasing textures

  - by user1642418

  I have a bit of a problem. I am developing a game for android + engine and I got stuck. I am getting OpenGL out of memory error and either app crashes or phone hangs after loading a scene multiple times. For example: app launches, shows main menu, 1st level/scene is loaded. Then I go back to main menu, and repeat. It doesnt matter which scene I load, after 4-6 times the error occurs. Some background: Each time when scene is loaded all the resources are released and upon first frame render - needed stuff gets loaded. The performance is more or less ok. Note that I am calling glDeleteTexture method, but I think its not doing its job and releasing memory. Thing is that -when I minimize and open it again - problem doesn't occur, but almost the same things are executed. Problem doesn't occur. This way android releases memory. How do I release/get rid of unused textures properly? This happens on HTC Desire HD ( ice cream sandwich 4.0.4) . Other games works fine, so I bet this is not the problem in ROM.

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• Android OpenGL es "glDrawTexfOES" draws upside down

  - by Alle

  I'm using OpenGL for Android to draw my 2D images. Whenever I draw something using the code: gl.glViewport(aspectRatioOffset, 0, screenWidth, screenHeight); gl.glMatrixMode(GL10.GL_PROJECTION); gl.glLoadIdentity(); GLU.gluOrtho2D(gl, aspectRatioOffset, screenWidth + aspectRatioOffset,screenHeight, 0); gl.glMatrixMode(GL10.GL_MODELVIEW); gl.glLoadIdentity(); gl.glEnable(GL10.GL_TEXTURE_2D); gl.glBindTexture(GL10.GL_TEXTURE_2D, myScene.neededGraphics.get(ID).get(animationID).get(animationIndex)); crop[0] = 0; crop[1] = 0; crop[2] = width; crop[3] = height; ((GL11Ext)gl).glDrawTexfOES(x, y, z, width, height) I get an upside down result. I'v seen people solve this through doing: crop[0] = 0; crop[1] = height; crop[2] = width; crop[3] = -height; This does however hurt the logic in my application, so I would like the result to not be flipped upside down. Does anyone know why it happen, and any way of avoiding or solving it?

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• OpenGL Pixel Format Attributes (NSOpenGLPixelFormatAttibutes) explanation?

  - by nacho4d

  Hi, I am not new to OpenGL, but not an expert. Many tutorials teach how to draw, 3D, 2D, projections, orthogonal, etc, but How about setting a the view? (NSOpenGLView in Cocoa, Macs). For example I have this: - (id) initWithFrame: (NSRect) frame { GLuint attribs[] = { //PF: PixelAttibutes NSOpenGLPFANoRecovery, NSOpenGLPFAWindow, NSOpenGLPFAAccelerated, NSOpenGLPFADoubleBuffer, NSOpenGLPFAColorSize, 24, NSOpenGLPFAAlphaSize, 8, NSOpenGLPFADepthSize, 24, NSOpenGLPFAStencilSize, 8, NSOpenGLPFAAccumSize, 0, 0 }; NSOpenGLPixelFormat* fmt = [[NSOpenGLPixelFormat alloc] initWithAttributes: (NSOpenGLPixelFormatAttribute*) attribs]; return self = [super initWithFrame:frame pixelFormat: [fmt autorelease]]; } And I don't understand very well their usage, specially when combining them. For example: If I want my view to be capable of full screen should I write NSOpenGLPFAFullScreen only ? or both? (by capable I mean not always in full screen) Regarding Double Buffer, what is this exactly? (Below: Apple's definition) If present, this attribute indicates that only double-buffered pixel formats are considered. Otherwise, only single-buffered pixel formats are considered Regarding Color: if NSOpenGLPFAColorSize is 24 and NSOpenGLPFAColorSize is 8 then it means that alpha and RGB components are treated differently? what happen if I set the former to 32 and the later to 0? Etc, etc,In general how do I learn to set my view from scratch? Thanks in advance. Ignacio.

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• iOS OpenGL ES 1.1 jerky animation using CADisplayLink (reboot fixes for a while)

  - by timthecoder

  I'm using OpenGL ES 1.1 and CADisplayLink to animate a 3d scene. If the iOS device has been rebooted fairly recently, the animation is smooth and the time delta between two displayLink.timestamp calls is fairly even. But after a few hours or days of the iOS device being used and my app is sometimes run a few times, the animation becomes jerky and the time deltas ramp up and then reset to a lower value only to ramp up again. Like this: 2012-09-01 23:42:58.770 [2678:707] dt= 0.021139 2012-09-01 23:42:58.787 [2678:707] dt= 0.022183 2012-09-01 23:42:58.804 [2678:707] dt= 0.023223 2012-09-01 23:42:58.820 [2678:707] dt= 0.024270 2012-09-01 23:42:58.837 [2678:707] dt= 0.009679 2012-09-01 23:42:58.853 [2678:707] dt= 0.010750 2012-09-01 23:42:58.870 [2678:707] dt= 0.011766 2012-09-01 23:42:58.887 [2678:707] dt= 0.012806 2012-09-01 23:42:58.903 [2678:707] dt= 0.013847 2012-09-01 23:42:58.920 [2678:707] dt= 0.014890 2012-09-01 23:42:58.937 [2678:707] dt= 0.015933 2012-09-01 23:42:58.953 [2678:707] dt= 0.016976 2012-09-01 23:42:58.970 [2678:707] dt= 0.018011 2012-09-01 23:42:58.987 [2678:707] dt= 0.019055 2012-09-01 23:42:59.003 [2678:707] dt= 0.020097 2012-09-01 23:42:59.020 [2678:707] dt= 0.021143 2012-09-01 23:42:59.037 [2678:707] dt= 0.022181 2012-09-01 23:42:59.054 [2678:707] dt= 0.023222 2012-09-01 23:42:59.071 [2678:707] dt= 0.024288 2012-09-01 23:42:59.087 [2678:707] dt= 0.009624 2012-09-01 23:42:59.103 [2678:707] dt= 0.010728 2012-09-01 23:42:59.121 [2678:707] dt= 0.011763 2012-09-01 23:42:59.137 [2678:707] dt= 0.012808 2012-09-01 23:42:59.153 [2678:707] dt= 0.013847 2012-09-01 23:42:59.170 [2678:707] dt= 0.014891 2012-09-01 23:42:59.187 [2678:707] dt= 0.016002 2012-09-01 23:42:59.203 [2678:707] dt= 0.016979 2012-09-01 23:42:59.220 [2678:707] dt= 0.018016 2012-09-01 23:42:59.237 [2678:707] dt= 0.019042 2012-09-01 23:42:59.253 [2678:707] dt= 0.020099 2012-09-01 23:42:59.270 [2678:707] dt= 0.021138 2012-09-01 23:42:59.287 [2678:707] dt= 0.022185 2012-09-01 23:42:59.304 [2678:707] dt= 0.023222 2012-09-01 23:42:59.320 [2678:707] dt= 0.024265 2012-09-01 23:42:59.337 [2678:707] dt= 0.009681 2012-09-01 23:42:59.354 [2678:707] dt= 0.010736 And then if the iOS device is rebooted the animation is smooth again. The problem even occurs on my menu screen when almost no game related calculations are going on in the UpdateAnimation() function. I don't understand what is going on and why a fresh reboot will always fix this problem for a while.

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• Build OpenGL model in parallel?

  - by Brendan Long

  I have a program which draws some terrain and simulates water flowing over it (in a cheap and easy way). Updating the water was easy to parallelize using OpenMP, so I can do ~50 updates per second. The problem is that even with a small amounts of water, my draws per second are very very low (starts at 5 and drops to around 2 once there's a significant amount of water). It's not a problem with the video card because the terrain is more complicated and gets drawn so quickly that boost::timer tells me that I get infinity draws per second if I turn the water off. It may be related to memory bandwidth though (since I assume the model stays on the card and doesn't have to be transfered every time). What I'm concerned about is that on every draw, I'm calling glVertex3f() about a million times (max size is 450*600, 4 vertices each), and it's done entirely sequentially because Glut won't let me call anything in parallel. So.. is if there's some way of building the list in parallel and then passing it to OpenGL all at once? Or some other way of making it draw this faster? Am I using the wrong method (besides the obvious "use less vertices")?

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• Overlay an image over video using OpenGL ES shaders

  - by BlueVoodoo

  I am trying to understand the basic concepts of OpenGL. A week into it, I am still far from there. Once I am in glsl, I know what to do but I find getting there is the tricky bit. I am currently able to pass in video pixels which I manipulate and present. I have then been trying to add still image as an overlay. This is where I get lost. My end goal is to end up in the same fragment shader with pixel data from both my video and my still image. I imagine this means I need two textures and pass on two pixel buffers. I am currently passing the video pixels like this: glGenTextures(1, &textures[0]); //target, texture glBindTexture(GL_TEXTURE_2D, textures[0]); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE); glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, width, height, 0, GL_BGRA, GL_UNSIGNED_BYTE, buffer); Would I then repeat this process on textures[1] with the second buffer from the image? If so, do I then bind both GL_TEXTURE0 and GL_TEXTURE1? ...and would my shader look something like this? uniform sampler2D videoData; uniform sampler2D imageData; once I am in the shader? It seems no matter what combination I try, image and video always ends up being just video data in both these. Sorry for the many questions merged in here, just want to clear my many assumptions and move on. To clarify the question a bit, what do I need to do to add pixels from a still image in the process described? ("easy to understand" sample code or any types of hints would be appreciated).

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• OpenGL GL_LINES enpoints not joining

  - by old-school rules

  I'm having problems with the GL_LINES block... the lines in the sample below do not connect on the ends (although sometimes it randomly decides to connect a corner or two). Instead, the endpoints come within 1 pixel of one another (leaving a corner that is not fully squared; if that makes sense). It is a simple block to draw a solid 1-pixel rectangle. glBegin(GL_LINES); glColor3b(cr, cg, cb); glVertex3i(pRect->left, pRect->top, 0); glVertex3i(pRect->right, pRect->top, 0); glVertex3i(pRect->right, pRect->top, 0); glVertex3i(pRect->right, pRect->bottom, 0); glVertex3i(pRect->right, pRect->bottom, 0); glVertex3i(pRect->left, pRect->bottom, 0); glVertex3i(pRect->left, pRect->bottom, 0); glVertex3i(pRect->left, pRect->top, 0); glEnd(); The sample below seems to correct the problem, giving me sharp, square corners; but I can't accept it because I don't know why it's acting this way... glBegin(GL_LINES); glColor3b(cr, cg, cb); glVertex3i(pRect->left, pRect->top, 0); glVertex3i(pRect->right + 1, pRect->top, 0); glVertex3i(pRect->right, pRect->top, 0); glVertex3i(pRect->right, pRect->bottom + 1, 0); glVertex3i(pRect->right, pRect->bottom, 0); glVertex3i(pRect->left - 1, pRect->bottom, 0); glVertex3i(pRect->left, pRect->bottom, 0); glVertex3i(pRect->left, pRect->top - 1, 0); glEnd(); Any OpenGL programmers out there that can help, I would appreciate it :)

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• State in OpenGL

  - by newprogrammer

  This is some simple code that draws to the screen. GLuint vbo; glGenBuffers(1, &vbo); glUseProgram(myProgram); glBindBuffer(GL_ARRAY_BUFFER, vbo); glEnableVertexAttribArray(0); glVertexAttribPointer(0, 4, GL_FLOAT, GL_FALSE, 0, 0); //Fill up my VBO with vertex data glBufferData(GL_ARRAY_BUFFER, sizeof(vertexes), &vertexes, GL_STATIC_DRAW); /*Draw to the screen*/ This works fine. However, I tried changing the order of some GL calls like so: GLuint vbo; glGenBuffers(1, &vbo); glUseProgram(myProgram); glEnableVertexAttribArray(0); glVertexAttribPointer(0, 4, GL_FLOAT, GL_FALSE, 0, 0); //Now comes after the setting of the vertex attributes. glBindBuffer(GL_ARRAY_BUFFER, vbo); //Fill up my VBO with vertex data glBufferData(GL_ARRAY_BUFFER, sizeof(vertexes), &vertexes, GL_STATIC_DRAW); /*Draw to the screen*/ This crashes my program. Why does there need to be a VBO bound to GL_ARRAY_BUFFER while I'm just setting up vertex attributes? To me, what glVertexAttribPointer does is just set up the format of vertexes that OpenGL will eventually use to draw things. It is not specific to any VBO. Thus, if multiple VBOs wanted to use the same vertex format, you would not need to format the vertexes in the VBO again.

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• Constant opacity with glBlendFunc on iPhone

  - by Jeff Johnson

  What glBlendFunc should I use to ensure that the opacity of my drawing is always the same? When I use glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA) and multiple images are drawn on top of each other, the result is more and more opaque until it's completely opaque after a certain number of imgaes. The closest I have come is to use glBlendFunc(GL_ONE_MINUS_DST_ALPHA, GL_ONE_MINUS_SRC_ALPHA) which maintains a constant opacity no matter how many images are on top of each other, although there is a slight variation in opacity if the images overlap each other. Any other render states I should consider trying? Any other ideas? I am making a drawing app for my kid and I don't want the images (brush) they draw to cover up the background. Heres the closest I've got: I want to have it so that the overlap part of the circles is the same color and opacity as the center part of the circle. I am using cocos2d iphone v. 0.99

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