Fix NaN on Intel GPU when using PBR Sky and rendering sun disk (#6145)

* Enable debug symbols

* tentative

* test using cos from cpu

* Finalize fix

* Missing file

* Remove debug symbols.

Author: FrancescoC-unity

com.unity.render-pipelines.high-definition/Runtime/RenderPipeline/HDStringConstants.cs

@@ -574,6 +574,7 @@ static class HDShaderIDs
         public static readonly int _SpaceEmissionMultiplier = Shader.PropertyToID("_SpaceEmissionMultiplier");
 
         public static readonly int _RenderSunDisk = Shader.PropertyToID("_RenderSunDisk");
+        public static readonly int _SunDiskCosines = Shader.PropertyToID("_SunDiskCosines");
 
         public static readonly int _ColorSaturation = Shader.PropertyToID("_ColorSaturation");
         public static readonly int _AlphaSaturation = Shader.PropertyToID("_AlphaSaturation");

com.unity.render-pipelines.high-definition/Runtime/Sky/PhysicallyBasedSky/PhysicallyBasedSky.shader

@@ -4,7 +4,6 @@ Shader "Hidden/HDRP/Sky/PbrSky"
 
     #pragma vertex Vert
 
-    // #pragma enable_d3d11_debug_symbols
     #pragma editor_sync_compilation
     #pragma target 4.5
     #pragma only_renderers d3d11 playstation xboxone xboxseries vulkan metal switch
@@ -26,6 +25,13 @@ Shader "Hidden/HDRP/Sky/PbrSky"
     float _GroundEmissionMultiplier;
     float _SpaceEmissionMultiplier;
 
+    // Inner and outer cosine computed as:
+    // float radInner = 0.5 * light.angularDiameter
+    // float cosInner = cos(radInner); // (In _SunDiskCosines.x)
+    // float cosOuter = cos(radInner + light.flareSize); // (In _SunDiskCosines.y)
+    // We need to pass it over instead of computing it here because on some vendors trigonometry has very bad precision, so we precompute what we can on CPU to have better precision.
+    float4 _SunDiskCosines;
+
     // Sky framework does not set up global shader variables (even per-view ones),
     // so they can contain garbage. It's very difficult to not include them, however,
     // since the sky framework includes them internally in many header files.
@@ -111,8 +117,9 @@ Shader "Hidden/HDRP/Sky/PbrSky"
                     float LdotV    = -dot(L, V);
                     float rad      = acos(LdotV);
                     float radInner = 0.5 * light.angularDiameter;
-                    float cosInner = cos(radInner);
-                    float cosOuter = cos(radInner + light.flareSize);
+
+                    float cosInner = _SunDiskCosines.x;
+                    float cosOuter = _SunDiskCosines.y;
 
                     float solidAngle = TWO_PI * (1 - cosInner);
 

com.unity.render-pipelines.high-definition/Runtime/Sky/PhysicallyBasedSky/PhysicallyBasedSkyRenderer.cs

@@ -500,6 +500,14 @@ public override void RenderSky(BuiltinSkyParameters builtinParams, bool renderFo
             }
             s_PbrSkyMaterialProperties.SetInt(HDShaderIDs._HasSpaceEmissionTexture, hasSpaceEmissionTexture);
 
+            // We need to pass it over instead of computing it here because on some vendors trigonometry has very bad precision, so we precompute what we can on CPU to have better precision.
+            // We can safely retrieve HDAdditionalLightData as for PBR sky the sunlight is always going to be an HDRP light.
+            var lightData = builtinParams.sunLight.gameObject.GetComponent<HDAdditionalLightData>();
+            float radInner = 0.5f * lightData.angularDiameter * Mathf.Deg2Rad;
+            float cosInner = Mathf.Cos(radInner);
+            float cosOuter = Mathf.Cos(radInner + lightData.flareSize);
+            s_PbrSkyMaterialProperties.SetVector(HDShaderIDs._SunDiskCosines, new Vector4(cosInner, cosOuter, 0, 0));
+
             s_PbrSkyMaterialProperties.SetInt(HDShaderIDs._RenderSunDisk, renderSunDisk ? 1 : 0);
 
             int pass = (renderForCubemap ? 0 : 2);