dolphin/Source/Core/VideoCommon/RenderState.cpp

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// Copyright 2016 Dolphin Emulator Project
// Licensed under GPLv2+
// Refer to the license.txt file included.
#include "VideoCommon/RenderState.h"
// If the framebuffer format has no alpha channel, it is assumed to
// ONE on blending. As the backends may emulate this framebuffer
// configuration with an alpha channel, we just drop all references
// to the destination alpha channel.
static BlendMode::BlendFactor RemoveDstAlphaUsage(BlendMode::BlendFactor factor)
{
switch (factor)
{
case BlendMode::DSTALPHA:
return BlendMode::ONE;
case BlendMode::INVDSTALPHA:
return BlendMode::ZERO;
default:
return factor;
}
}
// We separate the blending parameter for rgb and alpha. For blending
// the alpha component, CLR and ALPHA are indentical. So just always
// use ALPHA as this makes it easier for the backends to use the second
// alpha value of dual source blending.
static BlendMode::BlendFactor RemoveSrcColorUsage(BlendMode::BlendFactor factor)
{
switch (factor)
{
case BlendMode::SRCCLR:
return BlendMode::SRCALPHA;
case BlendMode::INVSRCCLR:
return BlendMode::INVSRCALPHA;
default:
return factor;
}
}
// Same as RemoveSrcColorUsage, but because of the overlapping enum,
// this must be written as another function.
static BlendMode::BlendFactor RemoveDstColorUsage(BlendMode::BlendFactor factor)
{
switch (factor)
{
case BlendMode::DSTCLR:
return BlendMode::DSTALPHA;
case BlendMode::INVDSTCLR:
return BlendMode::INVDSTALPHA;
default:
return factor;
}
}
void BlendingState::Generate(const BPMemory& bp)
{
// Start with everything disabled.
hex = 0;
bool target_has_alpha = bp.zcontrol.pixel_format == PEControl::RGBA6_Z24;
bool alpha_test_may_success = bp.alpha_test.TestResult() != AlphaTest::FAIL;
colorupdate = bp.blendmode.colorupdate && alpha_test_may_success;
alphaupdate = bp.blendmode.alphaupdate && target_has_alpha && alpha_test_may_success;
dstalpha = bp.dstalpha.enable && alphaupdate;
usedualsrc = true;
// The subtract bit has the highest priority
if (bp.blendmode.subtract)
{
blendenable = true;
subtractAlpha = subtract = true;
srcfactoralpha = srcfactor = BlendMode::ONE;
dstfactoralpha = dstfactor = BlendMode::ONE;
if (dstalpha)
{
subtractAlpha = false;
srcfactoralpha = BlendMode::ONE;
dstfactoralpha = BlendMode::ZERO;
}
}
// The blendenable bit has the middle priority
else if (bp.blendmode.blendenable)
{
blendenable = true;
srcfactor = bp.blendmode.srcfactor;
dstfactor = bp.blendmode.dstfactor;
if (!target_has_alpha)
{
// uses ONE instead of DSTALPHA
srcfactor = RemoveDstAlphaUsage(srcfactor);
dstfactor = RemoveDstAlphaUsage(dstfactor);
}
// replaces SRCCLR with SRCALPHA and DSTCLR with DSTALPHA, it is important to
// use the dst function for the src factor and vice versa
srcfactoralpha = RemoveDstColorUsage(srcfactor);
dstfactoralpha = RemoveSrcColorUsage(dstfactor);
if (dstalpha)
{
srcfactoralpha = BlendMode::ONE;
dstfactoralpha = BlendMode::ZERO;
}
}
// The logicop bit has the lowest priority
else if (bp.blendmode.logicopenable)
{
if (bp.blendmode.logicmode == BlendMode::NOOP)
{
// Fast path for Kirby's Return to Dreamland, they use it with dstAlpha.
colorupdate = false;
alphaupdate = alphaupdate && dstalpha;
}
else
{
logicopenable = true;
logicmode = bp.blendmode.logicmode;
if (dstalpha)
{
// TODO: Not supported by backends.
}
}
}
}