Make sure we get the correct lightmap decode parameters when in gamma mode

ScriptableRenderPipeline/Core/CoreRP/ShaderLibrary/EntityLighting.hlsl

 // It is required for other platform that aren't supporting this format to implement variant of these functions
 // (But these kind of platform should use regular render loop and not news shaders).
 
-// RGBM lightmaps are currently always gamma encoded, so we use a constant of range^2.2 = 5^2.2
-#define LIGHTMAP_RGBM_RANGE 34.493242
-
-// DLDR lightmaps are currently always gamma encoded, so we use a constant of 2.0^2.2 = 4.59
-#define LIGHTMAP_DLDR_RANGE 4.59
-
 // TODO: This is the max value allowed for emissive (bad name - but keep for now to retrieve it) (It is 8^2.2 (gamma) and 8 is the limit of punctual light slider...), comme from UnityCg.cginc. Fix it!
 // Ask Jesper if this can be change for HDRenderPipeline
 #define EMISSIVE_RGBM_SCALE 97.0
     return rgbm;
 }
 
-real3 UnpackLightmapRGBM(real4 rgbmInput)
+real3 UnpackLightmapRGBM(real4 rgbmInput, real4 decodeInstructions)
-    // RGBM lightmaps are always gamma encoded for now, so decode with that in mind:
-    return rgbmInput.rgb * pow(rgbmInput.a, 2.2) * LIGHTMAP_RGBM_RANGE;
+    return rgbmInput.rgb * pow(rgbmInput.a, decodeInstructions.y) * decodeInstructions.x;
-real3 UnpackLightmapDoubleLDR(real4 encodedColor)
+real3 UnpackLightmapDoubleLDR(real4 encodedColor, real4 decodeInstructions)
-    return encodedColor.rgb * LIGHTMAP_DLDR_RANGE;
+    return encodedColor.rgb * decodeInstructions.x;
-real3 DecodeLightmap(real4 encodedIlluminance)
+real3 DecodeLightmap(real4 encodedIlluminance, real4 decodeInstructions)
-    return UnpackLightmapRGBM(encodedIlluminance);
+    return UnpackLightmapRGBM(encodedIlluminance, decodeInstructions);
-    return UnpackLightmapDoubleLDR(encodedIlluminance);
+    return UnpackLightmapDoubleLDR(encodedIlluminance, decodeInstructions);
 #endif
 }
 
     return (decodeInstructions.x * pow(alpha, decodeInstructions.y)) * encodedIrradiance.rgb;
 }
 
-real3 SampleSingleLightmap(TEXTURE2D_ARGS(lightmapTex, lightmapSampler), float2 uv, float4 transform, bool encodedLightmap)
+real3 SampleSingleLightmap(TEXTURE2D_ARGS(lightmapTex, lightmapSampler), float2 uv, float4 transform, bool encodedLightmap, real4 decodeInstructions)
 {
     // transform is scale and bias
     uv = uv * transform.xy + transform.zw;
     {
         real4 encodedIlluminance = SAMPLE_TEXTURE2D(lightmapTex, lightmapSampler, uv).rgba;
-        illuminance = DecodeLightmap(encodedIlluminance);
+        illuminance = DecodeLightmap(encodedIlluminance, decodeInstructions);
     }
     else
     {
 }
 
-real3 SampleDirectionalLightmap(TEXTURE2D_ARGS(lightmapTex, lightmapSampler), TEXTURE2D_ARGS(lightmapDirTex, lightmapDirSampler), float2 uv, float4 transform, float3 normalWS, bool encodedLightmap)
+real3 SampleDirectionalLightmap(TEXTURE2D_ARGS(lightmapTex, lightmapSampler), TEXTURE2D_ARGS(lightmapDirTex, lightmapDirSampler), float2 uv, float4 transform, float3 normalWS, bool encodedLightmap, real4 decodeInstructions)
 {
     // In directional mode Enlighten bakes dominant light direction
     // in a way, that using it for half Lambert and then dividing by a "rebalancing coefficient"
     if (encodedLightmap)
     {
         real4 encodedIlluminance = SAMPLE_TEXTURE2D(lightmapTex, lightmapSampler, uv).rgba;
-        illuminance = DecodeLightmap(encodedIlluminance);
+        illuminance = DecodeLightmap(encodedIlluminance, decodeInstructions);
     }
     else
     {

ScriptableRenderPipeline/HDRenderPipeline/HDRP/Material/MaterialUtilities.hlsl

 
 #ifdef UNITY_LIGHTMAP_FULL_HDR
     bool useRGBMLightmap = false;
+    float4 decodeInstructions = float4(0.0, 0.0, 0.0, 0.0); // Never used but needed for the interface since it supports gamma lightmaps
+    #if defined(UNITY_LIGHTMAP_RGBM_ENCODING)
+        float4 decodeInstructions = float4(34.493242, 2.2, 0.0, 0.0); // range^2.2 = 5^2.2, gamma = 2.2
+    #else
+        float4 decodeInstructions = float4(0.0, 0.0, 0.0, 0.0); // range = 2.0^2.2 = 4.59
+    #endif
 #endif
 
     #ifdef LIGHTMAP_ON
-                                                        uvStaticLightmap, unity_LightmapST, normalWS, useRGBMLightmap);
+                                                        uvStaticLightmap, unity_LightmapST, normalWS, useRGBMLightmap, decodeInstructions);
-        bakeDiffuseLighting += SampleSingleLightmap(TEXTURE2D_PARAM(unity_Lightmap, samplerunity_Lightmap), uvStaticLightmap, unity_LightmapST, useRGBMLightmap);
+        bakeDiffuseLighting += SampleSingleLightmap(TEXTURE2D_PARAM(unity_Lightmap, samplerunity_Lightmap), uvStaticLightmap, unity_LightmapST, useRGBMLightmap, decodeInstructions);
+        float4 decodeInstructions = float4(0.0, 0.0, 0.0, 0.0); // Never used but needed for the interface since it supports gamma lightmaps
-                                                        uvDynamicLightmap, unity_DynamicLightmapST, normalWS, false);
+                                                        uvDynamicLightmap, unity_DynamicLightmapST, normalWS, false, decodeInstructions);
-        bakeDiffuseLighting += SampleSingleLightmap(TEXTURE2D_PARAM(unity_DynamicLightmap, samplerunity_DynamicLightmap), uvDynamicLightmap, unity_DynamicLightmapST, false);
+        bakeDiffuseLighting += SampleSingleLightmap(TEXTURE2D_PARAM(unity_DynamicLightmap, samplerunity_DynamicLightmap), uvDynamicLightmap, unity_DynamicLightmapST, false, decodeInstructions);
         #endif
     #endif
 

ScriptableRenderPipeline/LightweightPipeline/LWRP/ShaderLibrary/InputBuiltin.hlsl

 // HDR environment map decode instructions
 half4 unity_SpecCube0_HDR;
 
+// HDR lightmap decode instructions
+half4 unity_Lightmap_HDR;
+
 // These are set internally by the engine upon request by RendererConfiguration.
 // Check GetRendererSettings in LightweightPipeline.cs
 half4 unity_LightIndicesOffsetAndCount;

ScriptableRenderPipeline/LightweightPipeline/LWRP/ShaderLibrary/Lighting.hlsl

 #ifdef DIRLIGHTMAP_COMBINED
     return SampleDirectionalLightmap(TEXTURE2D_PARAM(unity_Lightmap, samplerunity_Lightmap),
         TEXTURE2D_PARAM(unity_LightmapInd, samplerunity_Lightmap),
-        lightmapUV, transformCoords, normalWS, encodedLightmap);
+        lightmapUV, transformCoords, normalWS, encodedLightmap, unity_Lightmap_HDR);
-    return SampleSingleLightmap(TEXTURE2D_PARAM(unity_Lightmap, samplerunity_Lightmap), lightmapUV, transformCoords, encodedLightmap);
+    return SampleSingleLightmap(TEXTURE2D_PARAM(unity_Lightmap, samplerunity_Lightmap), lightmapUV, transformCoords, encodedLightmap, unity_Lightmap_HDR);
 #endif
 }