Re: [PyOpenGL-Users] VBO question

[Jason H. <Jas...@vo...>]

Thanks for the reply Henry.  After a lot of trial and error, I finally figured out what the real problem is.  I'm on OpenGL 3.3 and glVertexPointer and the others have been deprecated since 3.0, but PyOpenGL tries to maintain backwards compatability I guess.  So I figured out the correct method and switched to glVertexAttribPointer and wrote a GLSL shader, now everything works great.

-Jason

________________________________________
From: Henry Gomersall [he...@ca...]
Sent: Monday, June 20, 2011 3:02 PM
To: pyo...@li...
Subject: Re: [PyOpenGL-Users] VBO question

On Mon, 2011-06-20 at 12:20 -0700, Jason Hayes wrote:
> # send vertices over to the GPU self.vbo_name = glGenBuffersARB( 1 )
> glBindBufferARB( GL_ARRAY_BUFFER_ARB, self.vbo_name )
> glBufferDataARB( GL_ARRAY_BUFFER_ARB, vertices, GL_STATIC_DRAW_ARB )

I'm not an expert, but don't you still need to copy the data to the
buffer. I'm not quite sure how you've managed with 3 arguments there
though. The docs all suggest you need 4.

After that I think you need to do something like (modified from my pbo
code, which is all in terms of numpy arrays, which are well laid out in
memory):

        # Map the buffer object to a pointer
        vbo_pointer = ctypes.cast(\
                GL.glMapBuffer(GL.GL_ARRAY_BUFFER, GL.GL_WRITE_ONLY),
                ctypes.POINTER(ctypes.c_ubyte))

        # Turn that pointer into a numpy array that spans
        # the whole block.(buffer size is the size of your buffer)
        vbo_array = numpy.ctypeslib.as_array(vbo_pointer,
                    (buffer_size,))

        vbo_array[0:data_size_to_copy] = \
                    data.view(dtype='uint8').ravel()

        # Unmap the buffer.
        GL.glUnmapBuffer(GL.GL_ARRAY_BUFFER)

Hope that helps.

cheers,

Henry


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