Re: [PATCH 3/5] wined3d: Don't clamp texture lookups in the GLSL fixed function fragment pipe.
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Am 2013-09-03 09:47, schrieb Henri Verbeet:
This originally came from the ARB fragment program implementation, but I don't see a justification for clamping there either. For the texture formats typically used with the fixed function pipe clamping wouldn't make a difference, and we don't have any tests that say we need to clamp.
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).
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.
On 3 September 2013 13:31, Stefan Dösinger stefandoesinger@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.
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Am 2013-09-03 13:41, schrieb Henri Verbeet:> 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.
That's interesting. I'd say that's a good motivation to remove them.
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Henri Verbeet -
Stefan Dösinger