Fix the orientation of area lights

Assets/ScriptableRenderPipeline/HDRenderPipeline/Lighting/TilePass/TilePass.cs

 
                     if (!lightData.twoSided)
                     {
-                        centerVS -= zAxisVS * radius * 0.5f;
+                        centerVS += zAxisVS * radius * 0.5f;
                         dimensions.z *= 0.5f;
                     }
 

Assets/ScriptableRenderPipeline/HDRenderPipeline/Material/Lit/Lit.hlsl

 
     [branch] if (lightData.cookieIndex >= 0 && illuminance > 0.0)
     {
-        float3 unL = positionWS - lightData.positionWS;
+        float3 lightToSurface = positionWS - lightData.positionWS;
-        // Project 'unL' onto the light's axes.
-        float2 coord = float2(dot(unL, lightData.right), dot(unL, lightData.up));
+        // Project 'lightToSurface' onto the light's axes.
+        float2 coord = float2(dot(lightToSurface, lightData.right), dot(lightToSurface, lightData.up));
 
         // Compute the NDC coordinates (in [-1, 1]^2).
         coord.x *= lightData.invScaleX;
     float  len = lightData.size.x;
     float3 T   = lightData.right;
 
-    float3 unL = positionWS - lightData.positionWS;
+    float3 unL = lightData.positionWS - positionWS;
 
     // Pick the major axis of the ellipsoid.
     float3 axis = lightData.right;
         float2 u = Hammersley2d(i, sampleCount);
         u = frac(u + randNum);
 
-        float4x4 localToWorld = float4x4(float4(lightData.right, 0.0), float4(lightData.up, 0.0), float4(lightData.forward, 0.0), float4(lightData.positionWS, 1.0));
+        // Lights in Unity point backward.
+        float4x4 localToWorld = float4x4(float4(lightData.right, 0.0), float4(lightData.up, 0.0), float4(-lightData.forward, 0.0), float4(lightData.positionWS, 1.0));
 
         switch (lightData.lightType)
         {
     float halfWidth  = lightData.size.x * 0.5;
     float halfHeight = lightData.size.y * 0.5;
 
-    float3 unL = positionWS - lightData.positionWS;
+    float3 unL = lightData.positionWS - positionWS;
-    float3x3 lightToWorld = float3x3(lightData.right, lightData.up, lightData.forward);
+    float3x3 lightToWorld = float3x3(lightData.right, lightData.up, -lightData.forward);
     unL = mul(unL, transpose(lightToWorld));
 
     // Define the dimensions of the attenuation volume.
     lightData.specularScale *= intensity;
 
     // TODO: store 4 points and save 12 cycles (24x MADs - 12x MOVs).
-    float3 p0 = lightData.positionWS + lightData.right * -halfWidth + lightData.up *  halfHeight;
-    float3 p1 = lightData.positionWS + lightData.right * -halfWidth + lightData.up * -halfHeight;
-    float3 p2 = lightData.positionWS + lightData.right *  halfWidth + lightData.up * -halfHeight;
-    float3 p3 = lightData.positionWS + lightData.right *  halfWidth + lightData.up *  halfHeight;
+    float3 p0 = lightData.positionWS + lightData.right *  halfWidth + lightData.up *  halfHeight;
+    float3 p1 = lightData.positionWS + lightData.right *  halfWidth + lightData.up * -halfHeight;
+    float3 p2 = lightData.positionWS + lightData.right * -halfWidth + lightData.up * -halfHeight;
+    float3 p3 = lightData.positionWS + lightData.right * -halfWidth + lightData.up *  halfHeight;
 
     float4x3 matL = float4x3(p0, p1, p2, p3) - float4x3(positionWS, positionWS, positionWS, positionWS);
 

Assets/TestScenes/HDTest/HDRenderLoopTest.unity

   affectDiffuse: 1
   affectSpecular: 1
   archetype: 1
-  isDoubleSided: 1
+  isDoubleSided: 0
   lightLength: 16
   lightWidth: 2
 --- !u!108 &827169275
   m_GameObject: {fileID: 827169273}
   m_Enabled: 1
   serializedVersion: 8
-  m_Type: 2
+  m_Type: 1
   m_Color: {r: 1, g: 1, b: 1, a: 1}
   m_Intensity: 1
   m_Range: 12
   affectDiffuse: 1
   affectSpecular: 1
   archetype: 1
-  isDoubleSided: 1
+  isDoubleSided: 0
   lightLength: 4
   lightWidth: 2
 --- !u!108 &1640077385
   m_GameObject: {fileID: 1640077383}
   m_Enabled: 1
   serializedVersion: 8
-  m_Type: 2
+  m_Type: 1
   m_Color: {r: 1, g: 1, b: 1, a: 1}
   m_Intensity: 1
   m_Range: 6