Question

I want to manipulate a texture which I use in opengl using CUDA. Knowing that I need to use a PBO for this I wonder if I have to recreate the texture every time I make changes to the PBO like this:

// Select the appropriate buffer
glBindBuffer( GL_PIXEL_UNPACK_BUFFER, bufferID);
// Select the appropriate texture
glBindTexture( GL_TEXTURE_2D, textureID);
// Make a texture from the buffer
glTexSubImage2D( GL_TEXTURE_2D, 0, 0, 0, Width, Height,GL_BGRA, GL_UNSIGNED_BYTE, NULL);

Does glTexSubImage2D and the like copy the data from the PBO?

Answer 1

All pixel transfer operations work with buffer objects. Since glTexSubImage2D initiates a pixel transfer operation, it can be used with buffer objects.

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There is no long-term connection made between buffer objects used for pixel transfers and textures. The buffer object is used much like a client memory pointer would be used for glTexSubImage2D calls. It’s there to store the data while OpenGL formats and pulls it into the texture. Once it’s done, you can do whatever you want with it.

The only difference is that, because OpenGL manages the buffer object, the upload from the buffer can be asynchronous. Well that and you get to play games like filling the buffer object from GPU operations (whether from OpenGL, OpenCL, or CUDA).