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PORender OpenGL ES 2.0 to image
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  1. PORender OpenGL ES 2.0 to image
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    copied!<p>I am trying to do some OpenGL ES 2.0 rendering to an image file, independent of the rendering being shown on the screen to the user. The image I'm rendering to is a different size than the user's screen. I just need a byte array of GL_RGB data. I'm familiar with glReadPixels, but I don't think it would do the trick in this case since I'm not pulling from an already-rendered user screen.</p> <p>Pseudocode:</p> <pre><code>// Switch rendering to another buffer (framebuffer? renderbuffer?) // Draw code here // Save byte array of rendered data GL_RGB to file // Switch rendering back to user's screen. </code></pre> <p>How can I do this without interrupting the user's display? I'd rather not have to flicker the user's screen, drawing my desired information for a single frame, glReadPixel-ing and then having it disappear.</p> <p>Again, I don't want it to show anything to the user. Here's my code. Doesn't work.. am I missing something?</p> <pre><code>unsigned int canvasFrameBuffer; bglGenFramebuffers(1, &amp;canvasFrameBuffer); bglBindFramebuffer(BGL_RENDERBUFFER, canvasFrameBuffer); unsigned int canvasRenderBuffer; bglGenRenderbuffers(1, &amp;canvasRenderBuffer); bglBindRenderbuffer(BGL_RENDERBUFFER, canvasRenderBuffer); bglRenderbufferStorage(BGL_RENDERBUFFER, BGL_RGBA4, width, height); bglFramebufferRenderbuffer(BGL_FRAMEBUFFER, BGL_COLOR_ATTACHMENT0, BGL_RENDERBUFFER, canvasRenderBuffer); unsigned int canvasTexture; bglGenTextures(1, &amp;canvasTexture); bglBindTexture(BGL_TEXTURE_2D, canvasTexture); bglTexImage2D(BGL_TEXTURE_2D, 0, BGL_RGB, width, height, 0, BGL_RGB, BGL_UNSIGNED_BYTE, 0); bglFramebufferTexture2D(BGL_FRAMEBUFFER, BGL_COLOR_ATTACHMENT0, BGL_TEXTURE_2D, canvasTexture, 0); Matrix::matrix_t identity; Matrix::LoadIdentity(&amp;identity); bglClearColor(1.0f, 1.0f, 1.0f, 1.0f); bglClear(BGL_COLOR_BUFFER_BIT); Draw(&amp;identity, &amp;identity, this); bglFlush(); bglFinish(); byte *buffer = (byte*)Z_Malloc(width * height * 4, ZT_STATIC); bglReadPixels(0, 0, width, height, BGL_RGB, BGL_UNSIGNED_BYTE, buffer); SaveTGA("canvas.tga", buffer, width, height); Z_Free(buffer); // unbind frame buffer bglBindRenderbuffer(BGL_RENDERBUFFER, 0); bglBindFramebuffer(BGL_FRAMEBUFFER, 0); bglDeleteTextures(1, &amp;canvasTexture); bglDeleteRenderbuffers(1, &amp;canvasRenderBuffer); bglDeleteFramebuffers(1, &amp;canvasFrameBuffer); </code></pre>
 

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