[PyOpenGL-Users] problem with soya's usage of OpenGL

[Christopher A. <ra...@tw...>]

Hello soya-user, hello pyopengl-users. This message isn't _totally_ 
relevant to pyopengl-users, but it's not unlikely that you guys have the 
requesite knowledge to help me fix this problem.

I've been trying to get Soya3d 
(http://home.gna.org/oomadness/en/soya/index.html) working for a while, 
but it's got problems with initialization. Soya3d talks to the OpenGL 
API directly with Pyrex. The problem is that a bunch of the calls it's 
making to OpenGL are returning NULL, while PyOpenGL calls to the same 
functions are returning expected values. At first we thought this was a 
problem with the way Soya was initializing GL (It uses SDL_Init to 
accomplish this), like it wasn't properly waiting for the OpenGL system 
to be initialized before it was making the calls. But to disprove that, 
I wrote this bit of Pyrex code:


.. inside of soya's init() function...
   from OpenGL import GL
   print "PyOGL:", GL.glGetString(GL.GL_VENDOR)
   my_dump_info()

cdef void my_dump_info():
   cdef char* gl_vendor
   gl_vendor = <char*> glGetString(GL_VENDOR)
   if gl_vendor == NULL:
     print "OGL: Wargh glGetString returned NULL"
     check_gl_error()
   else:
     print "OGL:", PyString_FromString(gl_vendor)


GL.glGetString was returning the expected "NVIDIA Corporation", but the 
direct call to the C glGetString is still returning NULL. The call to 
check_gl_error does a glCheckError, but that's returning GL_NO_ERROR. 
The same thing happens for stuff like glGetIntegerv.

So the only conclusion I can draw here is that somehow the PyOpenGL 
interface is calling these functions in a way that's different from 
pyrex's direct calls to them. I tried reading through the source of 
PyOpenGL but the SWIG stuff wasn't elucidative. It just seems like the 
wrappers are pretty direct. Does PyOpenGL involve some kind of different 
context that it might use where a direct call to the C interface wouldn't?

-- 
  Twisted | Christopher Armstrong: International Man of Twistery
   Radix  |          Release Manager,  Twisted Project
---------+           http://radix.twistedmatrix.com/