[osg-users] VBOs not actually used?

Thrall, Bryan bryan.thrall at flightsafety.com
Thu Mar 12 07:50:28 PDT 2009


Paul Melis wrote on Thursday, March 12, 2009 9:33 AM:

> Hi,
> 
> While trying to debug a collegue's code that uses a dynamically
updated
> color array on a Geometry that uses VBOs I'm getting confused about
VBO
> support in OSG 2.8.
> Given the attached simple .osg file (a single colored quad, flagged to
> not use display lists, but to use VBOs) I can see with an OpenGL
tracer
> (bugle) that no VBO is actually used on my nvidia FX5200 system. The
> quad is simply drawn using glVertex() and friends. Are there
limitations
> to when VBOs can be used? And, if so, is there a way to have OSG
loudly
> complain when a request for VBOs can not be satisfied?
> 
> Similarly, the attached c++ test case is more in line with our
original
> code. It uses a color array that is updated each frame. The array is
> flagged as dirty with a call to dirty(), but here also, no VBOs seem
to
> get used.
> 
> Regards,
> Paul
> 
> PS glxinfo reports GL_ARB_vertex_buffer_object is supported, OpenGL
> version is 2.1.0 NVIDIA 96.43.01

Binding PER_PRIMITIVE forces OSG out of fast path rendering, so I don't
think it can use VBOs. Using OVERALL or PER_VERTEX instead allowed VBOs
on my system.

-- 
Bryan Thrall
FlightSafety International
bryan.thrall at flightsafety.com



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