[osg-users] osg_Vertex with GL compatibility profile

Sebastian Messerschmidt sebastian.messerschmidt at gmx.de
Sat Sep 17 10:39:17 PDT 2016

Hi Ravi,
> Thanks Robert!
> So do you know why using osg_Vertex works *without* using setUseVertexAttributeAliasing() on so many machines? I am compiling OSG with GL2 (no GL3 flags) on all machines. Is it just "undocumented behavior"?
That is probably simply by chance, since the vertex attribute is usually 
the first one in the stream. The compiler will map the first attribute 
there. So basically this works most of the time.
> Next question: if I use setUseVertexAttributeAliasing, then many of my textured polygons (e.g. Sphere) have what appears to be a flat color on them. The actual color used seems to be related to one point on the texture.
> I see similar behavior if I run the "osgvertexattributes cow.osg" example (see attachment). Is Vertex Attribute Aliasing something that's only intended for GL3?
The cow model might not have texture coordinates but generated texture 
coordinates. I can't test the example right now, but maybe this is the 
reason. Usually when you go with vertex attribute aliasing you need to 
use an appropriate shader for the data.

> Ravi
> ------------------
> Read this topic online here:
> http://forum.openscenegraph.org/viewtopic.php?p=68641#68641
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