Re: [PyOpenGL-Users] gl*Pointer() VBO offsets

[Mike C. F. <mcf...@vr...>]

Alejandro Segovia wrote:
> Hi
>
> I've been working with VBO's to speed up my rendering time. I have an  
> array loaded with vertex data up to the middle and from there to the  
> end loaded with color data, but I'm having trouble setting the  
> appropriate offset in the glColorPointer() call.
>
> I've tried several approaches but they either raise an exception or  
> draw nothing. The only thing that seems to work is using None (which  
> automatically gets converted to NULL).
>   
This will be because it was creating a 1-element array of integers (the
offset) and then attempting to draw from it (duh).

> Does anyone know what would the correct idiom be for converting from  
> an int into the offset "pointer" needed by PyOpenGL?
>   
You need a ctypes.c_void_p( offset ), or if you're using
OpenGL.arrays.vbo.VBO, you can just pass (your_vbo + offset) which
creates an object whose array-value is ctypes.c_void_p( offset ).  There
was a bug in a 3.0.0 release (I believe a beta) that prevented
interpreting the c_void_p( offset ) correctly.  If it doesn't work, you
may need to update to a 3.0.1 beta.

HTH,
Mike

-- 
________________________________________________
  Mike C. Fletcher
  Designer, VR Plumber, Coder
  http://www.vrplumber.com
  http://blog.vrplumber.com