From be1832a348e9f6bcc41eb6ff429762a7f364cf3b Mon Sep 17 00:00:00 2001
From: Philip Rebohle <philip.rebohle@tu-dortmund.de>
Date: Sun, 24 Mar 2019 18:02:19 +0100
Subject: [PATCH] [d3d11] Don't sample gamma texture if the gamma curve is
 identity

Saves some GPU time in games that don't use DXGI gamma control at all.
---
 src/d3d11/d3d11_swapchain.cpp             | 33 ++++++++++++++---------
 src/d3d11/d3d11_swapchain.h               |  2 ++
 src/dxgi/shaders/dxgi_presenter_frag.frag | 16 ++++++-----
 3 files changed, 32 insertions(+), 19 deletions(-)

diff --git a/src/d3d11/d3d11_swapchain.cpp b/src/d3d11/d3d11_swapchain.cpp
index 7d099d37f..09b846f54 100644
--- a/src/d3d11/d3d11_swapchain.cpp
+++ b/src/d3d11/d3d11_swapchain.cpp
@@ -35,8 +35,6 @@ namespace dxvk {
     InitSamplers();
     InitShaders();
 
-    SetGammaControl(0, nullptr);
-
     // The present fence seems to introduce stutter on ANV
     if (m_device->adapter()->matchesDriver(DxvkGpuVendor::Intel, VK_DRIVER_ID_INTEL_OPEN_SOURCE_MESA_KHR, 0, 0))
       m_usePresentFence = false;
@@ -135,31 +133,34 @@ namespace dxvk {
   HRESULT STDMETHODCALLTYPE D3D11SwapChain::SetGammaControl(
           UINT                      NumControlPoints,
     const DXGI_RGB*                 pControlPoints) {
-    if (NumControlPoints > 0) {
+    bool isIdentity = true;
+
+    if (NumControlPoints > 1) {
       std::array<D3D11_VK_GAMMA_CP, 1025> cp;
 
       if (NumControlPoints > cp.size())
         return E_INVALIDARG;
       
       for (uint32_t i = 0; i < NumControlPoints; i++) {
+        uint16_t identity = MapGammaControlPoint(float(i) / float(NumControlPoints - 1));
+
         cp[i].R = MapGammaControlPoint(pControlPoints[i].Red);
         cp[i].G = MapGammaControlPoint(pControlPoints[i].Green);
         cp[i].B = MapGammaControlPoint(pControlPoints[i].Blue);
         cp[i].A = 0;
+
+        isIdentity &= cp[i].R == identity
+                   && cp[i].G == identity
+                   && cp[i].B == identity;
       }
 
-      CreateGammaTexture(NumControlPoints, cp.data());
-    } else {
-      std::array<D3D11_VK_GAMMA_CP, 256> cp;
-
-      for (uint32_t i = 0; i < cp.size(); i++) {
-        const uint16_t value = 257 * i;
-        cp[i] = { value, value, value, 0 };
-      }
-
-      CreateGammaTexture(cp.size(), cp.data());
+      if (!isIdentity)
+        CreateGammaTexture(NumControlPoints, cp.data());
     }
 
+    if (isIdentity)
+      DestroyGammaTexture();
+
     return S_OK;
   }
 
@@ -570,6 +571,12 @@ namespace dxvk {
   }
 
 
+  void D3D11SwapChain::DestroyGammaTexture() {
+    m_gammaTexture     = nullptr;
+    m_gammaTextureView = nullptr;
+  }
+
+
   void D3D11SwapChain::CreateHud() {
     m_hud = hud::Hud::createHud(m_device);
   }
diff --git a/src/d3d11/d3d11_swapchain.h b/src/d3d11/d3d11_swapchain.h
index 66d7d1b24..4099bb607 100644
--- a/src/d3d11/d3d11_swapchain.h
+++ b/src/d3d11/d3d11_swapchain.h
@@ -139,6 +139,8 @@ namespace dxvk {
             UINT                NumControlPoints,
       const D3D11_VK_GAMMA_CP*  pControlPoints);
     
+    void DestroyGammaTexture();
+    
     void CreateHud();
 
     void InitRenderState();
diff --git a/src/dxgi/shaders/dxgi_presenter_frag.frag b/src/dxgi/shaders/dxgi_presenter_frag.frag
index 73118a07a..7ff685156 100644
--- a/src/dxgi/shaders/dxgi_presenter_frag.frag
+++ b/src/dxgi/shaders/dxgi_presenter_frag.frag
@@ -1,5 +1,7 @@
 #version 450
 
+layout(constant_id = 3) const bool s_gamma_bound = false;
+
 layout(binding = 0) uniform sampler   s_sampler;
 layout(binding = 1) uniform texture2D t_texture;
 
@@ -10,11 +12,13 @@ layout(location = 0) in  vec2 i_texcoord;
 layout(location = 0) out vec4 o_color;
 
 void main() {
-  vec4 color = texture(sampler2D(t_texture, s_sampler), i_texcoord);
+  o_color = texture(sampler2D(t_texture, s_sampler), i_texcoord);
   
-  o_color = vec4(
-    texture(sampler1D(t_gamma, s_gamma), color.r).r,
-    texture(sampler1D(t_gamma, s_gamma), color.g).g,
-    texture(sampler1D(t_gamma, s_gamma), color.b).b,
-    color.a);
+  if (s_gamma_bound) {
+    o_color = vec4(
+      texture(sampler1D(t_gamma, s_gamma), o_color.r).r,
+      texture(sampler1D(t_gamma, s_gamma), o_color.g).g,
+      texture(sampler1D(t_gamma, s_gamma), o_color.b).b,
+      o_color.a);
+  }
 }
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