GS/DX11: Implement merge feedback write

bin/resources/shaders/dx11/convert.fx

@@ -18,6 +18,20 @@ struct VS_OUTPUT
 	float4 c : COLOR;
 };
 
+cbuffer cb0
+{
+	float4 BGColor;
+	int EMODA;
+	int EMODC;
+};
+
+static const float3x3 rgb2yuv =
+{
+	{0.587, 0.114, 0.299},
+	{-0.311, 0.500, -0.169},
+	{-0.419, -0.081, 0.500}
+};
+
 Texture2D Texture;
 SamplerState TextureSampler;
 
@@ -357,12 +371,50 @@ PS_OUTPUT ps_convert_rgba_8i(PS_INPUT input)
 	return output;
 }
 
-// DUMMY
 PS_OUTPUT ps_yuv(PS_INPUT input)
 {
 	PS_OUTPUT output;
 
-	output.c = input.p;
+	float4 i = sample_c(input.t);
+	float3 yuv = mul(rgb2yuv, i.gbr);
+
+	float Y = float(0xDB) / 255.0f * yuv.x + float(0x10) / 255.0f;
+	float Cr = float(0xE0) / 255.0f * yuv.y + float(0x80) / 255.0f;
+	float Cb = float(0xE0) / 255.0f * yuv.z + float(0x80) / 255.0f;
+
+	switch (EMODA)
+	{
+		case 0:
+			output.c.a = i.a;
+			break;
+		case 1:
+			output.c.a = Y;
+			break;
+		case 2:
+			output.c.a = Y / 2.0f;
+			break;
+		case 3:
+		default:
+			output.c.a = 0.0f;
+			break;
+	}
+
+	switch (EMODC)
+	{
+		case 0:
+			output.c.rgb = i.rgb;
+			break;
+		case 1:
+			output.c.rgb = float3(Y, Y, Y);
+			break;
+		case 2:
+			output.c.rgb = float3(Y, Cb, Cr);
+			break;
+		case 3:
+		default:
+			output.c.rgb = float3(i.a, i.a, i.a);
+			break;
+	}
 
 	return output;
 }

bin/resources/shaders/dx11/merge.fx

@@ -6,6 +6,9 @@ SamplerState Sampler;
 cbuffer cb0
 {
 	float4 BGColor;
+	int EMODA;
+	int EMODC;
+	int cb0_pad[2];
 };
 
 struct PS_INPUT

pcsx2/GS/Renderers/Common/GSDevice.h

@@ -74,6 +74,9 @@ class MergeConstantBuffer
 {
 public:
 	GSVector4 BGColor;
+	u32 EMODA;
+	u32 EMODC;
+	u32 pad[2];
 
 	MergeConstantBuffer() { memset(this, 0, sizeof(*this)); }
 };

pcsx2/GS/Renderers/DX11/GSDevice11.cpp

@@ -724,21 +724,54 @@ void GSDevice11::StretchRect(GSTexture* sTex, const GSVector4& sRect, GSTexture*
 
 void GSDevice11::DoMerge(GSTexture* sTex[3], GSVector4* sRect, GSTexture* dTex, GSVector4* dRect, const GSRegPMODE& PMODE, const GSRegEXTBUF& EXTBUF, const GSVector4& c)
 {
-	const bool slbg = PMODE.SLBG;
-	const bool mmod = PMODE.MMOD;
+	const GSVector4 full_r(0.0f, 0.0f, 1.0f, 1.0f);
+	const bool feedback_write_2 = PMODE.EN2 && sTex[2] != nullptr && EXTBUF.FBIN == 1;
+	const bool feedback_write_1 = PMODE.EN1 && sTex[2] != nullptr && EXTBUF.FBIN == 0;
+	const bool feedback_write_2_but_blend_bg = feedback_write_2 && PMODE.SLBG == 1;
 
+	// Merge the 2 source textures (sTex[0],sTex[1]). Final results go to dTex. Feedback write will go to sTex[2].
+	// If either 2nd output is disabled or SLBG is 1, a background color will be used.
+	// Note: background color is also used when outside of the unit rectangle area
 	ClearRenderTarget(dTex, c);
 
-	if (sTex[1] && !slbg)
+	// Upload constant to select YUV algo, but skip constant buffer update if we don't need it
+	if (feedback_write_2 || feedback_write_1 || sTex[0])
 	{
-		StretchRect(sTex[1], sRect[1], dTex, dRect[1], m_merge.ps[0].get(), nullptr, true);
+		MergeConstantBuffer cb;
+		cb.BGColor = c;
+		cb.EMODA = EXTBUF.EMODA;
+		cb.EMODC = EXTBUF.EMODC;
+		m_ctx->UpdateSubresource(m_merge.cb.get(), 0, nullptr, &cb, 0, 0);
 	}
 
+	if (sTex[1] && (PMODE.SLBG == 0 || feedback_write_2_but_blend_bg))
+	{
+		// 2nd output is enabled and selected. Copy it to destination so we can blend it with 1st output
+		// Note: value outside of dRect must contains the background color (c)
+		StretchRect(sTex[1], sRect[1], dTex, dRect[1], ShaderConvert::COPY);
+	}
+
+	// Save 2nd output
+	if (feedback_write_2)
+	{
+		StretchRect(dTex, full_r, sTex[2], dRect[1], m_convert.ps[static_cast<int>(ShaderConvert::YUV)].get(),
+			m_merge.cb.get(), nullptr, true);
+	}
+
+	// Restore background color to process the normal merge
+	if (feedback_write_2_but_blend_bg)
+		ClearRenderTarget(dTex, c);
+
 	if (sTex[0])
 	{
-		m_ctx->UpdateSubresource(m_merge.cb.get(), 0, nullptr, &c, 0, 0);
+		// 1st output is enabled. It must be blended
+		StretchRect(sTex[0], sRect[0], dTex, dRect[0], m_merge.ps[PMODE.MMOD].get(), m_merge.cb.get(), m_merge.bs.get(), true);
+	}
 
-		StretchRect(sTex[0], sRect[0], dTex, dRect[0], m_merge.ps[mmod ? 1 : 0].get(), m_merge.cb.get(), m_merge.bs.get(), true);
+	if (feedback_write_1)
+	{
+		StretchRect(dTex, full_r, sTex[2], dRect[0], m_convert.ps[static_cast<int>(ShaderConvert::YUV)].get(),
+			m_merge.cb.get(), nullptr, true);
 	}
 }