2021.1 Universal/fix aces filter (#3776)

* Promoted some color conversion functions to full floating point precision for Switch platform in order to fix ACES tonemapping artefact.
This issue does not affect other mobile platforms.

* Made floating point fixes permanent to all platforms.

Author: kaychang-unity

com.unity.render-pipelines.core/CHANGELOG.md

@@ -19,6 +19,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 - Fixed ACES tonemaping for Nintendo Switch by forcing some shader color conversion functions to full float precision.
 - Fixed missing warning UI about Projector component being unsupported (case 1300327).
 - Fixed the display name of a Volume Parameter when is defined the attribute InspectorName
+- Fixed ACES tonemaping on mobile platforms by forcing some shader color conversion functions to full float precision.
 - Fix crash on VolumeComponentWithQualityEditor when the current Pipeline is not HDRP
 
 ## [10.2.0] - 2020-10-19

com.unity.render-pipelines.core/ShaderLibrary/Color.hlsl

@@ -254,7 +254,7 @@ real YCoCgCheckBoardEdgeFilter(real centerLum, real2 a0, real2 a1, real2 a2, rea
 }
 
 // Converts linear RGB to LMS
-real3 LinearToLMS(real3 x)
+float3 LinearToLMS(float3 x) // Full float precision to avoid precision artefact when using ACES tonemapping
 {
     const real3x3 LIN_2_LMS_MAT = {
         3.90405e-1, 5.49941e-1, 8.92632e-3,
@@ -265,7 +265,7 @@ real3 LinearToLMS(real3 x)
     return mul(LIN_2_LMS_MAT, x);
 }
 
-real3 LMSToLinear(real3 x)
+float3 LMSToLinear(float3 x) // Full float precision to avoid precision artefact when using ACES tonemapping
 {
     const real3x3 LMS_2_LIN_MAT = {
         2.85847e+0, -1.62879e+0, -2.48910e-2,
@@ -395,7 +395,7 @@ real LinearToLogC_Precise(real x)
     return o;
 }
 
-real3 LinearToLogC(real3 x)
+float3 LinearToLogC(float3 x) // Full float precision to avoid precision artefact when using ACES tonemapping
 {
 #if USE_PRECISE_LOGC
     return real3(
@@ -418,7 +418,7 @@ real LogCToLinear_Precise(real x)
     return o;
 }
 
-real3 LogCToLinear(real3 x)
+float3 LogCToLinear(float3 x) // Full float precision to avoid precision artefact when using ACES tonemapping
 {
 #if USE_PRECISE_LOGC
     return real3(