Make DXT alpha and color calculation more accurate #11530
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Hardware tests show that this shouldn't happen. May be important for color tests, etc.
Hardware tests show this is how it decodes, which is more like standard DXT1 decoding.
Hardware draws using 2/3. Adding this way matches rounding, too.
Hardware is still doing DXT1 style colors in this scenario.
Hardware doesn't seem to.
This isn't quite right, but it seems better than rounding down. Experimented with a lower round up value, but none were right - the weighting must be more complex.
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Regarding the rounding, could it be that the two multiplications are rounded to 8-bit or 9-bit separately before they are summed? Either way, great job figuring this out! |
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Yeah, I was thinking it's probably that, although it generally rounds up... -[Unknown] |
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This matches tests fairly well, except the DXT5 alpha case - it rounds slightly wrong for some alpha values.
With these changes, Gran Turismo looks pretty much the same as the GE dump played on real hardware. So fixes #5685.
There's still some mystery bits in that dump, but it doesn't seem like they do anything (didn't heavily test them though.)
-[Unknown]