From 0e5633db072d50ceb21bfe8c15678d9d2fc9890f Mon Sep 17 00:00:00 2001
From: pastasfuture <pastasfuture@gmail.com>
Date: Mon, 9 Aug 2021 10:27:04 -0700
Subject: [PATCH] Bugfix: CRT Shader Vertical Flip Logic

---
 CHANGELOG.md                               |  5 +++++
 Runtime/PostProcessing/Shaders/CRT.shader  | 14 +++++---------
 Runtime/ShaderLibrary/ShaderFunctions.hlsl | 20 ++++++++++++++++++++
 3 files changed, 30 insertions(+), 9 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 92c40e3..4881e1f 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,8 @@
+---------------------------------------------------------------------------------------------------------------------------
+Bugfix: **CRT Shader Vertical Flip Logic**
+---------------------------------------------------------------------------------------------------------------------------
+Fixed bug where some CameraVolume aspect modes did not render correctly on hardware that requires flipped Y in the CRT shader.
+
 ---------------------------------------------------------------------------------------------------------------------------
 New Material Feature: **Vertex Color Blend Modes**
 ---------------------------------------------------------------------------------------------------------------------------
diff --git a/Runtime/PostProcessing/Shaders/CRT.shader b/Runtime/PostProcessing/Shaders/CRT.shader
index 9a27592..930bf9b 100644
--- a/Runtime/PostProcessing/Shaders/CRT.shader
+++ b/Runtime/PostProcessing/Shaders/CRT.shader
@@ -475,26 +475,22 @@ Shader "Hidden/HauntedPS1/CRT"
         UNITY_SETUP_STEREO_EYE_INDEX_POST_VERTEX(input);
 
         float2 positionFramebufferNDC = input.uvFramebuffer;
-        float2 positionFramebufferSS = input.uvFramebuffer * _ScreenSize.xy;
-
         float2 positionScreenNDC = input.uvScreen;
-        float2 positionScreenSS = input.uvScreen * _ScreenSize.xy;
-
+        
     #if UNITY_SINGLE_PASS_STEREO
         positionFramebufferNDC.x = (positionFramebufferNDC.x + unity_StereoEyeIndex) * 0.5;
         positionScreenNDC.x = (positionScreenNDC.x + unity_StereoEyeIndex) * 0.5;
     #endif
 
-        // Flip logic
         if (ShouldFlipY())
         {
-            positionFramebufferSS.y = _ScreenSize.y - 1.0 - positionFramebufferSS.y;
-            positionFramebufferNDC.y = 1.0 - positionFramebufferNDC.y;
-
-            positionScreenSS.y = _ScreenSize.y - 1.0 - positionScreenSS.y;
+            positionFramebufferNDC = ComputeRasterizationRTUVFlipVerticallyInBounds(positionFramebufferNDC);
             positionScreenNDC.y = 1.0 - positionScreenNDC.y;
         }
 
+        float2 positionFramebufferSS = input.uvFramebuffer * _ScreenSize.xy;
+        float2 positionScreenSS = input.uvScreen * _ScreenSize.xy;
+
         if (!_IsPSXQualityEnabled || !_CRTIsEnabled)
         {
             return ComputeRasterizationRTUVIsInBounds(positionFramebufferNDC.xy)
diff --git a/Runtime/ShaderLibrary/ShaderFunctions.hlsl b/Runtime/ShaderLibrary/ShaderFunctions.hlsl
index be6be22..b9f9d61 100644
--- a/Runtime/ShaderLibrary/ShaderFunctions.hlsl
+++ b/Runtime/ShaderLibrary/ShaderFunctions.hlsl
@@ -495,4 +495,24 @@ bool ComputeRasterizationRTPositionSSIsInBounds(float2 positionSS)
         && (positionSS.y <= _RasterizationRTScaledMaxSSAndUV.y);
 }
 
+float2 ComputeRasterizationRTUVFlipVerticallyInBounds(float2 uv)
+{
+    return ComputeRasterizationRTUVIsInBounds(uv)
+        ? float2(
+            uv.x,
+            _RasterizationRTScaledMaxSSAndUV.w - uv.y
+        )
+        : uv;
+}
+
+float2 ComputeRasterizationRTPositionSSFlipVerticallyInBounds(float2 positionSS)
+{
+    return ComputeRasterizationRTPositionSSIsInBounds(positionSS)
+        ? float2(
+            positionSS.x,
+            _RasterizationRTScaledMaxSSAndUV.y - positionSS.y
+        )
+        : positionSS;
+}
+
 #endif
\ No newline at end of file