rendering: formalize main light shadow params

engine/assets/builtin/shaders/forward-lit.shader

@@ -25,6 +25,21 @@ Shader "Builtin Forward Lit"
         float4 spotAnglesAndFlags;
     };
 
+    struct ShadowMapMetrics
+    {
+        float2 inverseMapSize;
+        float worldTexelSize;
+        float padding;
+    };
+
+    struct ShadowSamplingData
+    {
+        float enabled;
+        float receiverDepthBias;
+        float normalBiasScale;
+        float shadowStrength;
+    };
+
     cbuffer LightingConstants
     {
         float4 gMainLightDirectionAndIntensity;
@@ -42,8 +57,8 @@ Shader "Builtin Forward Lit"
     cbuffer ShadowReceiverConstants
     {
         float4x4 gWorldToShadowMatrix;
-        float4 gShadowBiasAndTexelSize;
-        float4 gShadowOptions;
+        ShadowMapMetrics gShadowMapMetrics;
+        ShadowSamplingData gShadowSampling;
     };
 
     Texture2D BaseColorTexture;
@@ -83,12 +98,13 @@ Shader "Builtin Forward Lit"
     #ifndef XC_MAIN_LIGHT_SHADOWS
         return 1.0f;
     #else
-        if (gShadowOptions.x < 0.5f) {
+        if (gShadowSampling.enabled < 0.5f) {
             return 1.0f;
         }
 
         const float nDotL = saturate(dot(normalize(normalWS), normalize(lightDirectionWS)));
-        const float normalBiasWorld = gShadowOptions.y * gShadowOptions.z * (1.0f - nDotL);
+        const float normalBiasWorld =
+            gShadowMapMetrics.worldTexelSize * gShadowSampling.normalBiasScale * (1.0f - nDotL);
         const float3 shadowPositionWS = positionWS + normalize(normalWS) * normalBiasWorld;
         const float4 shadowClip = mul(gWorldToShadowMatrix, float4(shadowPositionWS, 1.0f));
         if (shadowClip.w <= 0.0f) {
@@ -109,7 +125,7 @@ Shader "Builtin Forward Lit"
             return 1.0f;
         }
 
-        const float receiverDepth = shadowNdc.z * 0.5f + 0.5f - gShadowBiasAndTexelSize.x;
+        const float receiverDepth = shadowNdc.z * 0.5f + 0.5f - gShadowSampling.receiverDepthBias;
     #else
         if (shadowUv.x < 0.0f || shadowUv.x > 1.0f ||
             shadowUv.y < 0.0f || shadowUv.y > 1.0f ||
@@ -117,9 +133,9 @@ Shader "Builtin Forward Lit"
             return 1.0f;
         }
 
-        const float receiverDepth = shadowNdc.z - gShadowBiasAndTexelSize.x;
+        const float receiverDepth = shadowNdc.z - gShadowSampling.receiverDepthBias;
     #endif
-        const float2 shadowTexelSize = gShadowBiasAndTexelSize.yz;
+        const float2 shadowTexelSize = gShadowMapMetrics.inverseMapSize;
         float visibility = 0.0f;
     [unroll]
         for (int offsetY = -1; offsetY <= 1; ++offsetY) {
@@ -139,7 +155,7 @@ Shader "Builtin Forward Lit"
         }
 
         visibility *= (1.0f / 9.0f);
-        const float shadowStrength = saturate(gShadowBiasAndTexelSize.w);
+        const float shadowStrength = saturate(gShadowSampling.shadowStrength);
         return lerp(1.0f - shadowStrength, 1.0f, visibility);
     #endif
     }