Am Donnerstag, 29. November 2007 08:31:40 schrieb Aras Pranckevicius:
> > This particular issue would be great to see as a proper ARB extension
> > or as part of OpenGL 3.0. From conversations with people at both
> > Apple and NVIDIA
>
> There is GL_NV_float_buffer that defines R and RG renderable formats
> (on par with D3D9). Unfortunately it's not exposed on the Macs... But
> the extension does exist.
>
> Could Apple please implement support for that? Single and dual channel
> floating point renderables are SO useful for various things (writing
> high precision linear depth, variance shadow mapping, ...). Wasting 4X
> or 2X more VRAM amount and bandwidth is just plain silly.
The issue with them is that they work only with GL_ARB_texture_rectangle, not
other textures. Texture rectangles have a number of limitations and
strangeness, like no mipmapping, and non-normalized coordinates, which makes
them unsuitable in many situations.
Another issue with formats like GL_R32F_NV is the value they return for green
and blue when sampled. D3D returns 1.0, the gl format returns 0.0. This is
not really an issue if you're writing an app and you can deal with that, but
if you're trying to run unmodified D3D apps it is a real PITA. Of course I
could just adjust that in the shader, but then the shader depends on the
formats and is incompatible with other formats.
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