Add support for directional light

all in one formula for spot, light and directional light

Assets/ScriptableRenderLoop/HDRenderLoop/HDRenderLoop.cs

             for (int lightIndex = 0; lightIndex < Math.Min(activeLights.Length, MaxLights); lightIndex++)
             {
                 ActiveLight light = activeLights[lightIndex];
-                if (light.lightType == LightType.Spot || light.lightType == LightType.Point)
+                if (light.lightType == LightType.Spot || light.lightType == LightType.Point || light.lightType == LightType.Directional)
-                    l.positionWS = light.light.transform.position;
-                    l.invSqrAttenuationRadius  = 1.0f / (light.range * light.range);
+                    if (light.lightType == LightType.Directional)
+                    {
+                        l.useDistanceAttenuation = 0.0f;
+                        // positionWS store Light direction for directional and is opposite to the forward direction
+                        l.positionWS = -light.light.transform.forward;
+                        l.invSqrAttenuationRadius = 0.0f;
+                    }
+                    else
+                    {
+                        l.useDistanceAttenuation = 1.0f;
+                        l.positionWS = light.light.transform.position;
+                        l.invSqrAttenuationRadius = 1.0f / (light.range * light.range);
+                    }
 
                     // Correct intensity calculation (Different from Unity)
                     float lightColorR = light.light.intensity * Mathf.GammaToLinearSpace(light.light.color.r);
                     l.color = new Vec3(lightColorR, lightColorG, lightColorB);
 
-                    // Light direction is opposite to the forward direction...
+                    // Light direction is opposite to the forward direction
                     l.forward = -light.light.transform.forward;
                     // CAUTION: For IES as we inverse forward maybe this will need rotation.
                     l.up = light.light.transform.up;
 		                // 1.0f, 2.0f are neutral value allowing GetAngleAnttenuation in shader code to return 1.0
                         l.angleScale = 1.0f;
                         l.angleOffset = 2.0f;
-	                }                  
+	                }
 
                     lights.Add(l);
                     punctualLightCount++;

Assets/ScriptableRenderLoop/HDRenderLoop/Shaders/LightDefinition.cs

         public float invSqrAttenuationRadius;
 
         public Vec3 color;
-        public float unused;
+        public float useDistanceAttenuation;
 
         public Vec3 forward;
         public float diffuseScale;

Assets/ScriptableRenderLoop/HDRenderLoop/Shaders/Material/DisneyGGX.hlsl

 							out float4 diffuseLighting,
 							out float4 specularLighting)
 {
-	float3 unL = light.positionWS - positionWS;
+	// All punctual light type in the same formula, attenuation is neutral depends on light type.
+	// light.positionWS is the normalize light direction in case of directional light and invSqrAttenuationRadius is 0
+	// mean dot(unL, unL) = 1 and mean GetDistanceAttenuation() will return 1
+	// For point light and directional GetAngleAttenuation() return 1
+
+	float3 unL = light.positionWS - positionWS * light.useDistanceAttenuation;
-	// Always done, directional have it neutral
-	// Always done, point and dir have it neutral
 	attenuation *= GetAngleAttenuation(L, light.forward, light.angleScale, light.angleOffset);
 	float illuminance = saturate(dot(material.normalWS, L)) * attenuation;
 

Assets/ScriptableRenderLoop/HDRenderLoop/Shaders/PostProcess/FinalPass.shader

 			{
 				float4 c = tex2D(_MainTex, input.texcoord);
 				// Gamma correction
-				return LinearToSRGB(c);
+
+				// TODO: Currenlt in the editor there a an additional pass were the result is copyed in a render target RGBA8_sRGB.
+				// So we must not correct the sRGB here else it will be done two time.
+				// To fix!
+
+				// return LinearToSRGB(c);
+				return c;
+
+				
 			}
 			ENDCG 
 

Assets/TestScenes/HDTest/HDRenderLoopTest.unity

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Assets/TestScenes/HDTest/Material/Terrain.mat

       second: {r: 0.5, g: 0.5, b: 0.5, a: 1}
     - first:
         name: _DiffuseColor
-      second: {r: 0.5808823, g: 0.5808823, b: 0.5808823, a: 1}
+      second: {r: 0.7176471, g: 0.7176471, b: 0.7176471, a: 1}
     - first:
         name: _EmissionColor
       second: {r: 0, g: 0, b: 0, a: 1}

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