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POTrying to render to texture using framebuffer always results in white texture
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copied!<p>Using a couple of posts here in StackOverflow, I created what is supposed to be a simple render-to-texture using a framebuffer.</p> <p>The problem here is that it's not working. Something is broken in the mix, as my final texture is just a white square. I am not getting any gl errors whatsoever. Here is my code.</p> <p>Declare instance variables.</p> <pre><code>GLuint texture; GLuint textureFrameBuffer; </code></pre> <p>Generate the texture and framebuffer.</p> <pre><code> glGetError(); //Generate the texture that we will draw to (saves us a lot of processor). glEnable(GL_TEXTURE_2D); glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR); // Use OpenGL ES to generate a name for the texture. // Pass by reference so that our texture variable gets set. glGenTextures(1, &texture); // Bind the texture name. glBindTexture(GL_TEXTURE_2D, texture); // Specify a 2D texture image, providing a pointer to the image data in memory. glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, 512, 128, 0, GL_RGBA, GL_UNSIGNED_BYTE, NULL); //Create a frame buffer to draw to. This will allow us to directly edit the texture. GLint oldFBO; glGetIntegerv(GL_FRAMEBUFFER_BINDING_OES, &oldFBO); glGenFramebuffersOES(1, &textureFrameBuffer); glBindFramebufferOES(GL_FRAMEBUFFER_OES, textureFrameBuffer); glFramebufferTexture2DOES(GL_FRAMEBUFFER_OES, GL_COLOR_ATTACHMENT0_OES, GL_TEXTURE_2D, texture, 0); glBindFramebufferOES(GL_FRAMEBUFFER_OES, oldFBO); GLenum err = glGetError(); if (err != GL_NO_ERROR) { NSLog(@"Error on framebuffer init. glError: 0x%04X", err); } </code></pre> <p>Draw a big string into the framebuffer.</p> <pre><code>glGetError(); GLint oldFBO; glGetIntegerv(GL_FRAMEBUFFER_BINDING_OES, &oldFBO); //Bind our frame buffer. glBindFramebufferOES(GL_FRAMEBUFFER_OES, textureFrameBuffer); //Clear out the texture. glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); //Draw the letters to the frame buffer. (calls glDrawArrays a bunch of times, binds various textures, etc.) Does everything in 2D. [self renderDialog:displayString withSprite:displaySprite withName:displaySpriteName]; //Unbind the frame buffer. glBindFramebufferOES(GL_FRAMEBUFFER_OES, oldFBO); GLenum err = glGetError(); if (err != GL_NO_ERROR) { NSLog(@"Error on string creation. glError: 0x%04X", err); } </code></pre> <p>Draw it.</p> <pre><code> glColor4f(1.0f, 1.0f, 1.0f, 1.0f); glGetError(); //Draw the text. [EAGLView enable2D]; //Push the matrix so we can keep it as it was previously. glPushMatrix(); //Store the coordinates/dimensions from the rectangle. float x = 0; float y = [Globals getPlayableHeight] - dialogRect.size.height; float w = [Globals getPlayableWidth]; float h = dialogRect.size.height; // Set up an array of values to use as the sprite vertices. GLfloat vertices[] = { x, y, x, y+h, x+w, y+h, x+w, y }; // Set up an array of values for the texture coordinates. GLfloat texcoords[] = { 0, 0, 0, h / 128, w / 512, h / 128, w / 512, 0 }; //Render the vertices by pointing to the arrays. glVertexPointer(2, GL_FLOAT, 0, vertices); glTexCoordPointer(2, GL_FLOAT, 0, texcoords); // Set the texture parameters to use a linear filter when minifying. glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_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); //Allow transparency and blending. glEnable(GL_BLEND); glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA); //Enable 2D textures. glEnable(GL_TEXTURE_2D); //Bind this texture. [EAGLView bindTexture:texture]; //Finally draw the arrays. glDrawArrays(GL_TRIANGLE_FAN, 0, 4); //Restore the model view matrix to prevent contamination. glPopMatrix(); GLenum err = glGetError(); if (err != GL_NO_ERROR) { NSLog(@"Error on draw. glError: 0x%04X", err); } </code></pre> <p>Any external things I called work just fine in other contexts. Any ideas? I know almost nothing about framebuffers, so any help troubleshooting would be great.</p>

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