Using ARRAY_BUFFER’s in PyOpenGL

I’m in the process of converting my code from Pyglet GL to PyOpenGL.
In doing so, my VBO objects stopped rendering.

It turns out the problem is glVertexAttribPointer.
The Pyglet GL version takes the last parameter (offset) as a number. I set this to 0 for arrays with no offset.

glVertexAttribPointer( in_position, 3, GL_FLOAT, GL_FALSE, 0, 0)

It seems that PyOpenGL expects the pointer value by absolute instead of relative.
The solution is to pass None instead of 0.

glVertexAttribPointer( in_position, 3, GL_FLOAT, GL_FALSE, 0, None)

If you have an actual offset to pass, you need to convert to a ctypes c_void_p (void*).
http://stackoverflow.com/questions/11132716/how-to-specify-buffer-offset-with-pyopengl

glVertexAttribPointer( in_position, 3, GL_FLOAT, GL_FALSE, 0, ctypes.c_void_p(offset))

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2 Responses to “Using ARRAY_BUFFER’s in PyOpenGL”

  1. The 2nd time I’ve landed on this page in two days πŸ™‚

    I think this should be considered a bug in pyopengl – either in the documentation, or a feature worth implementing.

    It’s certainly confusing when you’ve been looking at webgl examples.

  2. Hello, thank you very much for this post. I’ve spend a ton of time trying to figure out why opengl takes no color from my vba. None offset was the problem and it finaly works now.
    Thank you πŸ™‚

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