Replace Cs*As + Cd*(1 - As) with Cs*As - Cd*(As - 1).
Replace Cs*F + Cd*(1 - F) with Cs*F - Cd*(F - 1).
As - 1 or F - 1 subtraction is only done for the dual source output (hw blending part)
since we are changing the equation.
Af will be replaced with As in shader and send it to dual source output.
Also check if A*Alpha in the shader overflows, if it does then adjust the
alpha that is sent for HW blending further to compensate.
Idea is to replace Ad with As when alpha write is masked,
then expand/let blend mix, accumulation blend non recursive blend or hw clr blend to
do the blending with Ad swapped as As.
We are doing this to try to bring some originally higher blending modes to lower levels
where we can do the draws with less texture barriers instead (gl/vk),
as for d3d11 this allows to run blending on the draws since previously the cases weren't handled properly,
it will be slower on d3d11 since we will be reading the frame buffer but it's better than nothing.
D3D11: It is enabled on Medium blending or higher, if draw is fbmask then it will enable
it on basic blending too.
OpenGL/Vulkan:
It is enabled based on the previous blending modes:
accumulation blend -> either minimum or basic level, depending on colclamp.
non recursive blend -> either minimum or basic level, depending on colclamp.
blend mix -> basic and higher level.
hw clr blend -> minimum and higher level.
All:
Prefer full sw blend when primitives don't overlap, sw fbmask or full barrier is used, it is more accurate.
Having this binding was redundant, as there's no "normal" texture
sampled when we're doing a channel shuffle, and it caused issues in
Vulkan when the render target or depth buffer the source.
Also fixes the Urban Chaos HLE shader.
Fixes validation errors in GT4, NFS: Carbon, Urban Chaos, probably
others too.
Alpha destination value is wrong so let us try to compensate.
Multiply Cs by (255/128) in shader.
Will work best if Cs is 0.5 or less, if it's higher than 0.5 then the closer to 1 the less accurate it gets.
Ofc it is best to use sw blending but it will help if sw blending is not present/selected for specific draw, will help d3d11 quite more.
Do hw blend for Cd*As, Cd*F, expand the clear color blend method as it is almost the same.
Most helpful for dx11 ofc, for gl/vulkan will help with rendering on lower
levels of blending without needing a barrier.
Clamp the alpha(As/Af) to 1 in the shader, it is already clamped to 1 in hw blend unit.
It should allow to better render the effects, still not fully accurate but it's closer to what we want.
Hopefully it helps D3D11 more.
Connor McLaughlin