I’d like to use fragment/vertex shaders, however I have a GeForce4 TI 4200, so I’ve only Vextex shader and NV_Combiners in hardware, but no Fragment Shader at all.
So i’d like to know what effects it’s possible to build only with Vertex shader ? And if it’s possible to combine Vertex Shader and NV_Combiner to have something similar to Vertex+Fragment shader structure.
On top of that, I read that it’s possible to use Fragment Shader with DirectX (software emulation). Is it possible to have an emulation with OpenGL too?
Yes, you can achieve a fragment shader similar environment with register combiner and texture shader on NV. But these extensions are relative unflexible compared to fragment programs or fragment shaders.
But remember, NV_register_combiner and NV_texture_shader are only available on NV hardware. But there’s a similar extension on ATI: ATI_fragment_shader.
There is an emulation tool for NV where you can use them on your graphics card. Send a Mail to NV developer relation. There also is mesa (www.mesa3d.org), a software OpenGL implementation, which has ARB_*_program support.
NVidia has a tool called NVemulate which you can find from other sites.
for example, this guy is running Dawn in emulation which probably takes minutes to render 1 frame. http://www.mcbridematt.dhs.org/at0mic/dawn/