Support RenderViewportScale

Traditional screen-space RenderViewportScale support is done through _MainTex_ST.  However, we don't use Graphics.Blit or CommandBuffer.Blit for most blits, so we can't rely on that infrastructure.

Instead, we can wrap our usage of unity_StereoScaleOffset/TransformStereoScreenSpaceTex with an RVS scaler.  This works pretty well, and makes the RenderViewportScale management very explicit and obvious.

There might be an issue with WindowsMR, as it doesn't guarantee the RenderViewportScale value will actually be used (yeah...), but we'll cross that bridge when we get there.

Author: robbiesri

PostProcessing/Runtime/PostProcessLayer.cs

@@ -273,7 +273,14 @@ void OnPreCull()
             m_Camera.nonJitteredProjectionMatrix = m_Camera.projectionMatrix;
 
             if (XRSettings.isDeviceActive)
+            {
                 m_Camera.ResetStereoProjectionMatrices();
+                Shader.SetGlobalFloat("rvsGlobal", XRSettings.renderViewportScale);
+            }
+            else
+            {
+                Shader.SetGlobalFloat("rvsGlobal", 1.0f);
+            }
 
             BuildCommandBuffers();
         }

PostProcessing/Shaders/Builtins/CopyStd.shader

@@ -33,12 +33,15 @@ Shader "Hidden/PostProcessing/CopyStd"
         {
             Varyings o;
             o.vertex = float4(v.vertex.xy * 2.0 - 1.0, 0.0, 1.0);
-            o.texcoord = v.texcoord * _MainTex_ST.xy + _MainTex_ST.zw; // We need this for VR
+            o.texcoord = v.texcoord;
 
             #if UNITY_UV_STARTS_AT_TOP
             o.texcoord = o.texcoord * float2(1.0, -1.0) + float2(0.0, 1.0);
             #endif
 
+            o.texcoord = o.texcoord * _MainTex_ST.xy + _MainTex_ST.zw; // We need this for VR
+
+
             return o;
         }
 

PostProcessing/Shaders/xRLib.hlsl

@@ -24,6 +24,8 @@ CBUFFER_START(UnityStereoEyeIndex)
 CBUFFER_END
 #endif
 
+float rvsGlobal;
+
 float2 UnityStereoScreenSpaceUVAdjust(float2 uv, float4 scaleAndOffset)
 {
     return uv.xy * scaleAndOffset.xy + scaleAndOffset.zw;
@@ -38,6 +40,7 @@ float4 UnityStereoScreenSpaceUVAdjust(float4 uv, float4 scaleAndOffset)
 float2 TransformStereoScreenSpaceTex(float2 uv, float w)
 {
     float4 scaleOffset = unity_StereoScaleOffset[unity_StereoEyeIndex];
+    scaleOffset.xy *= rvsGlobal;
     return uv.xy * scaleOffset.xy + scaleOffset.zw * w;
 }
 
@@ -58,11 +61,20 @@ float2 UnityStereoClampScaleOffset(float2 uv, float4 scaleAndOffset)
 
 float2 UnityStereoClamp(float2 uv)
 {
+    // TODO: Factor in RVS?
     return UnityStereoClampScaleOffset(uv, unity_StereoScaleOffset[unity_StereoEyeIndex]);
 }
 #else
-#define TransformStereoScreenSpaceTex(uv, w) uv
-#define UnityStereoTransformScreenSpaceTex(uv) uv
+float2 TransformStereoScreenSpaceTex(float2 uv, float w)
+{
+    return uv * rvsGlobal;
+}
+
+float2 UnityStereoTransformScreenSpaceTex(float2 uv)
+{
+    return TransformStereoScreenSpaceTex(saturate(uv), 1.0);
+}
+
 #define UnityStereoClampScaleOffset(uv, scaleAndOffset) uv
 #define UnityStereoClamp(uv) uv
 #endif