[PATCH 3/5] wined3d: Don't clamp texture lookups in the GLSL fixed function fragment pipe.

[Henri Verbeet]

On 3 September 2013 13:31, Stefan Dösinger <stefandoesinger at gmail.com> wrote:
> The idea behind the clamps is that the fixed function pipeline is
> generally limited to the [0.0;1.0] range. bbf313e7 added a test for
> that, and there was e.g. 14706 (which doesn't contain much info tbh).
>
Yes, but that's for stage operations, where it kind of makes sense,
and on most hardware is just an instruction modifier. For texture
sampling operations it's more questionable, and the driver can't
necessarily just use an instruction modifier.

> Personally I'd keep the clamps in unless a test says otherwise or
> there's another compelling reason to remove them. But since it is
> quite unlikely to matter that's not a strong opinion. The ideal
> solution is of course to write a test.
>
It ends up being a performance bottleneck in some cases. This is
particularly visible in the 3DMark03 multi-texture fill-rate test, in
other cases the impact is usually a bit more modest.