From e426ec09a1f5d02aa7b1589c40c083235df9df41 Mon Sep 17 00:00:00 2001
From: Philip Rebohle <philip.rebohle@tu-dortmund.de>
Date: Sun, 8 Jan 2023 00:51:13 +0100
Subject: [PATCH] [d3d11,dxbc] Add d3d11.forceSampleRateShading option

---
 dxvk.conf                   | 9 +++++++++
 src/d3d11/d3d11_options.cpp | 1 +
 src/d3d11/d3d11_options.h   | 5 +++++
 src/dxbc/dxbc_compiler.cpp  | 8 ++++++++
 src/dxbc/dxbc_options.cpp   | 1 +
 src/dxbc/dxbc_options.h     | 4 ++++
 6 files changed, 28 insertions(+)

diff --git a/dxvk.conf b/dxvk.conf
index b5635a6e..473ca91b 100644
--- a/dxvk.conf
+++ b/dxvk.conf
@@ -201,6 +201,15 @@
 # d3d9.invariantPosition = True
 
 
+# Forces per-sample rate shading when MSAA is enabled, rather than per-pixel
+# shading. May improve visual clarity at a significant performance cost, but
+# may also introduce visual issues in some games.
+#
+# Supported values: True, False
+
+# d3d11.forceSampleRateShading = False
+
+
 # Forces the sample count of all textures to 1, and performs
 # the needed fixups in resolve operations and shaders.
 #
diff --git a/src/d3d11/d3d11_options.cpp b/src/d3d11/d3d11_options.cpp
index f4eee5b2..bcac396b 100644
--- a/src/d3d11/d3d11_options.cpp
+++ b/src/d3d11/d3d11_options.cpp
@@ -23,6 +23,7 @@ namespace dxvk {
     this->samplerLodBias        = config.getOption<float>("d3d11.samplerLodBias", 0.0f);
     this->invariantPosition     = config.getOption<bool>("d3d11.invariantPosition", true);
     this->floatControls         = config.getOption<bool>("d3d11.floatControls", true);
+    this->forceSampleRateShading = config.getOption<bool>("d3d11.forceSampleRateShading", false);
     this->disableMsaa           = config.getOption<bool>("d3d11.disableMsaa", false);
     this->enableContextLock     = config.getOption<bool>("d3d11.enableContextLock", false);
     this->deferSurfaceCreation  = config.getOption<bool>("dxgi.deferSurfaceCreation", false);
diff --git a/src/d3d11/d3d11_options.h b/src/d3d11/d3d11_options.h
index 1b636db1..99bca076 100644
--- a/src/d3d11/d3d11_options.h
+++ b/src/d3d11/d3d11_options.h
@@ -99,6 +99,11 @@ namespace dxvk {
     /// for a single window that may interfere with each other.
     bool deferSurfaceCreation;
 
+    /// Enables sample rate shading by interpolating fragment shader
+    /// inputs at the sample location rather than pixel center,
+    /// unless otherwise specified by the application.
+    bool forceSampleRateShading;
+
     /// Forces the sample count of all textures to be 1, and
     /// performs the required shader and resolve fixups.
     bool disableMsaa;
diff --git a/src/dxbc/dxbc_compiler.cpp b/src/dxbc/dxbc_compiler.cpp
index f5664f87..fb107da6 100644
--- a/src/dxbc/dxbc_compiler.cpp
+++ b/src/dxbc/dxbc_compiler.cpp
@@ -726,6 +726,14 @@ namespace dxvk {
         m_module.decorate(varId, spv::DecorationSample);
       }
 
+      if (m_moduleInfo.options.forceSampleRateShading) {
+        if (im == DxbcInterpolationMode::Linear
+         || im == DxbcInterpolationMode::LinearNoPerspective) {
+          m_module.enableCapability(spv::CapabilitySampleRateShading);
+          m_module.decorate(varId, spv::DecorationSample);
+        }
+      }
+
       // Declare the input slot as defined
       m_inputMask |= 1u << regIdx;
       m_vArrayLength = std::max(m_vArrayLength, regIdx + 1);
diff --git a/src/dxbc/dxbc_options.cpp b/src/dxbc/dxbc_options.cpp
index 0d848679..e642a0df 100644
--- a/src/dxbc/dxbc_options.cpp
+++ b/src/dxbc/dxbc_options.cpp
@@ -38,6 +38,7 @@ namespace dxvk {
     zeroInitWorkgroupMemory  = options.zeroInitWorkgroupMemory;
     forceVolatileTgsmAccess  = options.forceVolatileTgsmAccess;
     disableMsaa              = options.disableMsaa;
+    forceSampleRateShading   = options.forceSampleRateShading;
     enableSampleShadingInterlock = device->features().extFragmentShaderInterlock.fragmentShaderSampleInterlock;
 
     // Figure out float control flags to match D3D11 rules
diff --git a/src/dxbc/dxbc_options.h b/src/dxbc/dxbc_options.h
index b29cf5d4..2612a024 100644
--- a/src/dxbc/dxbc_options.h
+++ b/src/dxbc/dxbc_options.h
@@ -43,6 +43,10 @@ namespace dxvk {
     /// Replace ld_ms with ld
     bool disableMsaa = false;
 
+    /// Force sample rate shading by using sample
+    /// interpolation for fragment shader inputs
+    bool forceSampleRateShading = false;
+
     // Enable per-sample interlock if supported
     bool enableSampleShadingInterlock = false;