StackOverflow2013

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POMultisampled rendering to texture
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copied!<p>I am working with the following architecture:</p> <ul> <li>OpenGL ES 2 on iOS</li> <li>Two EAGL contexts with the same ShareGroup</li> <li>Two threads (server, client = main thread); the server renders stuff to textures, the client displays the textures using simple textured quads.</li> </ul> <p><strong>Additional detail to the server thread (working code)</strong></p> <p>An fbo is created during initialization:</p> <pre><code>void init(void) { glGenFramebuffer(1, &fbo); } </code></pre> <p>The render loop of the server looks roughly like this:</p> <pre><code>GLuint loop(void) { glBindFrameBuffer(GL_FRAMEBUFFER, fbo); glViewport(0,0,width,height); GLuint tex; glGenTextures(1, &tex); glBindTexture(GL_TEXTURE_2D, tex); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_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_RGB, width, height, 0, GL_RGB, GL_UNSIGNED_BYTE, NULL); glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, tex, 0); // Framebuffer completeness check omitted glClear(GL_COLOR_BUFFER_BIT); // actual drawing code omitted // the drawing code bound other textures, so.. glBindTexture(GL_TEXTURE_2D, tex); glGenerateMipmap(GL_TEXTURE_2D); glBindTexture(GL_TEXTURE_2D, GL_NONE); glFlush(); return tex; } </code></pre> <p>All this works fine so far.</p> <p><strong>New (buggy) code</strong></p> <p>Now i want to add Multisampling to the server thread, using the GL_APPLE_framebuffer_multisample extension and modified the the initialization code like this:</p> <pre><code>void init(void) { glGenFramebuffer(1, &resolve_fbo); glGenFramebuffers(1, &sample_fbo); glBindFramebuffer(GL_FRAMEBUFFER, sample_fbo); glGenRenderbuffers(1, &sample_colorRenderbuffer); glBindRenderbuffer(GL_RENDERBUFFER, sample_colorRenderbuffer); glRenderbufferStorageMultisampleAPPLE(GL_RENDERBUFFER, 4, GL_RGBA8_OES, width, height); glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_RENDERBUFFER, sample_colorRenderbuffer); // Framebuffer completeness check (sample_fbo) omitted glBindRenderbuffer(GL_RENDERBUFFER, GL_NONE); glBindFramebuffer(GL_FRAMEBUFFER, GL_NONE); } </code></pre> <p>The main loop has been changed to:</p> <pre><code>GLuint loop(void) { glBindFrameBuffer(GL_FRAMEBUFFER, sample_fbo); glViewport(0,0,width,height); GLuint tex; glGenTextures(1, &tex); glBindTexture(GL_TEXTURE_2D, tex); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_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_RGB, width, height, 0, GL_RGB, GL_UNSIGNED_BYTE, NULL); glClear(GL_COLOR_BUFFER_BIT); // actual drawing code omitted glBindFramebuffer(GL_FRAMEBUFFER, resolve_fbo); glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, tex, 0); // Framebuffer completeness check (resolve_fbo) omitted // resolve multisampling glBindFramebuffer(GL_DRAW_FRAMEBUFFER_APPLE, resolve_fbo); glBindFramebuffer(GL_READ_FRAMEBUFFER_APPLE, sample_fbo); glResolveMultisampleFramebufferAPPLE(); // the drawing code bound other textures, so.. glBindTexture(GL_TEXTURE_2D, tex); glGenerateMipmap(GL_TEXTURE_2D); glBindTexture(GL_TEXTURE_2D, GL_NONE); glFlush(); return tex; } </code></pre> <p>What i see now is that a texture contains data from multiple loop() calls, blended together. I guess I'm either missing an 'unbind' of some sort, or probably a <code>glFinish()</code> call (I previously had such a problem at a different point, I set texture data with <code>glTexImage2D()</code> and used it right afterwards - that required a <code>glFinish()</code> call to force the texture to be updated).</p> <p>However inserting a <code>glFinish()</code> after the drawing code didn't change anything here..</p>

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