[osg-users] Running OSG models on OpenGLES2.0

Sebastian Messerschmidt sebastian.messerschmidt at gmx.de
Mon Mar 14 09:53:53 PDT 2016

Am 14.03.2016 um 17:35 schrieb Chris Hanson:
>     Can't you try some other GLES applications(plain OpenGL-ES without
>     OSG) and check their shader code? I believe there is a problem
>     with your system/driver, as there is no need to explicitly issuing
>     the precision in normal cases.
>   I thought some drivers were more strict about this?
>   I remember having some embedded GLES drivers having fits until we 
> added precision qualifiers, and maybe some desktop ones did at some 
> point too.
That would be strange but not impossible in the world of OpenGL-Drivers ;-)
I read the OpenGL ES shading language as "you don't need to put 
precision qualifiers unless" (Any floating point ... can have the type 
preceeded 4.7.3 "Precision Qualifiers") followed by the 4.7.4 which 
seems to explain it.
There are deafult precisions for float in the vertex shader, but not in 
the fragment shader

"The fragment language has no default precision qualifier for floating 
point types.  Hence for float, floating
point vector and matrix variable declarations, either the declaration 
must include a precision qualifier or
the default float precision must have been previously declared. 
Similarly, there is no default precision
qualifier for any of the image types,  or any of the following sampler 
types in any of the languages:"

So basically I always had the luck to have sloppy drivers :-) and one 
must indeed add the precision qualifiers or define the default precision.


> -- 
> Chris 'Xenon' Hanson, omo sanza lettere. Xenon at AlphaPixel.com 
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