Fix light flare for pbr sky (#6278)

* Fix Template directional light

* Fix when using multiple directional lights with flare

* restore default flare on template

Co-authored-by: sebastienlagarde <sebastien@unity3d.com>

Author: adrien-de-tocqueville

com.unity.render-pipelines.high-definition/Runtime/Lighting/Light/HDGpuLightsBuilder.Jobs.cs

@@ -683,6 +683,12 @@ private void ConvertDirectionalLightToGPUFormat(
 
                 lightData.flareSize = Mathf.Max(lightRenderData.flareSize * Mathf.Deg2Rad, 5.960464478e-8f);
                 lightData.flareFalloff = lightRenderData.flareFalloff;
+
+                // On some vendors trigonometry has very bad precision, so we precompute what we can on CPU to avoid precision issues (case 1369376).
+                float radInner = 0.5f * lightData.angularDiameter;
+                lightData.flareCosInner = Mathf.Cos(radInner);
+                lightData.flareCosOuter = Mathf.Cos(radInner + lightData.flareSize);
+
                 lightData.flareTint = (Vector3)(Vector4)lightRenderData.flareTint;
                 lightData.surfaceTint = (Vector3)(Vector4)lightRenderData.surfaceTint;
 

com.unity.render-pipelines.high-definition/Runtime/Lighting/LightDefinition.cs

@@ -99,12 +99,16 @@ struct DirectionalLightData
 
         public float diffuseDimmer;
         public float specularDimmer;
+
         public float penumbraTint;
         public float isRayTracedContactShadow;
 
         public float distanceFromCamera;      // -1 -> no sky interaction
         public float angularDiameter;         // Units: radians
+
         public float flareFalloff;
+        public float flareCosInner;
+        public float flareCosOuter;
         public float __unused__;
 
         public Vector3 flareTint;

com.unity.render-pipelines.high-definition/Runtime/Lighting/LightDefinition.cs.hlsl

@@ -80,6 +80,8 @@ struct DirectionalLightData
     float distanceFromCamera;
     float angularDiameter;
     float flareFalloff;
+    float flareCosInner;
+    float flareCosOuter;
     float __unused__;
     float3 flareTint;
     float flareSize;

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

@@ -581,7 +581,6 @@ 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

@@ -4,6 +4,7 @@ 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
@@ -25,13 +26,6 @@ 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.
@@ -118,19 +112,16 @@ Shader "Hidden/HDRP/Sky/PbrSky"
                     float rad      = acos(LdotV);
                     float radInner = 0.5 * light.angularDiameter;
 
-                    float cosInner = _SunDiskCosines.x;
-                    float cosOuter = _SunDiskCosines.y;
-
-                    float solidAngle = TWO_PI * (1 - cosInner);
+                    float solidAngle = TWO_PI * (1 - light.flareCosInner);
 
-                    if (LdotV >= cosOuter)
+                    if (LdotV >= light.flareCosOuter)
                     {
                         // Sun flare is visible. Sun disk may or may not be visible.
                         // Assume uniform emission.
                         float3 color = light.color.rgb;
                         float  scale = rcp(solidAngle);
 
-                        if (LdotV >= cosInner) // Sun disk.
+                        if (LdotV >= light.flareCosInner) // Sun disk.
                         {
                             tFrag = lightDist;
 

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

@@ -500,14 +500,6 @@ 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);

com.unity.template-hd/Assets/Scenes/SampleScene.unity

@@ -28899,9 +28899,9 @@ MonoBehaviour:
   m_UseScreenSpaceShadows: 0
   m_InteractsWithSky: 1
   m_AngularDiameter: 0.53
-  m_FlareSize: 0
-  m_FlareTint: {r: 0, g: 0, b: 0, a: 1}
-  m_FlareFalloff: 0
+  m_FlareSize: 2
+  m_FlareTint: {r: 1, g: 1, b: 1, a: 1}
+  m_FlareFalloff: 4
   m_SurfaceTexture: {fileID: 0}
   m_SurfaceTint: {r: 1, g: 1, b: 1, a: 1}
   m_Distance: 150000000