From: Alexander Lechner (alexander.lechner++at++vertigo-systems.de)
Date: 08/15/2003 05:58:43
Hi All!
I appreciate very much the work of the Performer team!
It was great news to hear that there will be support for Vertex/Fragment
shaders/programs in Performer 3.1 via a high level shading language. As
someone already pointed out glslang (OpenGL Shading Language) will be the
underlying technology.
I have some questions regarding this topic:
(1) Will the vertex/fragment programm support be on GeoState or GeoSet
level?
(2) What about the interface to provide the shaders with data?
For example it should be possible to plug-in a phong shader and provide
it with all Performer light sources currently enabled.
Of course shaders can access the current GL state (which lights are
enabled, which materials) but this would be a bit tedious. Stay
high-level!
(3) What about support for Cube-Textures and NPOT (non power of two)
textures?
Of course one can apply its own pfGeoState apply callback and create
these things by oneself, but this interferes with Performers GeoState
inheritance aso. Also, if you have multiple GLX contexts (pfPipeWindows)
you have to check whether to create a new texture object, download the
texture aso. (replicating all things which pfState already does, see
pfState.h)
In my opinion these are key features when Vertex/Fragment shaders are
to be supported.
(4) Also, (sorry) one big problem with OpenGL performer is the rendering
performance. Why not supporting the Vertex Buffer Object extension?
Or some of the driver specific extensions like NV_vertex_array.
I think the new Onyx4 could also profit from this.
Of course one can write its own GeoSetCB but again it is very
tedious of writing its own rendering and managing per GLXcontext data.
(5) What about the current state of rendering to textures or pbuffers.
Is this working under linux? Would be cool for doing multi pass
rendering, for example a cube reflection map with the actual scene
rendered.
Any opinions?
Keep up your excellent work!
Alex
-- Alexander.Lechner ++at++ vertigo-systems.de Engelbertstraße 30 | phone: +49-221-2405472 D-50674 Köln | fax: +49-221-34892616
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