Fix for shadow atlas not being cleared correctly

Source/Engine/Renderer/ShadowsPass.cpp

@@ -1413,7 +1413,11 @@ void ShadowsPass::RenderShadowMaps(RenderContextBatch& renderContextBatch)
                 if (!shadows.ClearStaticShadowMapAtlas)
                 {
                     // Color.r is used by PS_DepthClear in Quad shader to clear depth
+#if FLAX_REVERSE_Z
+                    quadShaderData.Color = Float4::Zero;
+#else
                     quadShaderData.Color = Float4::One;
+#endif
                     context->UpdateCB(quadShaderCB, &quadShaderData);
                     context->BindCB(0, quadShaderCB);
 
@@ -1480,7 +1484,11 @@ void ShadowsPass::RenderShadowMaps(RenderContextBatch& renderContextBatch)
             else if (!shadows.ClearShadowMapAtlas)
             {
                 // Color.r is used by PS_DepthClear in Quad shader to clear depth
+#if FLAX_REVERSE_Z
+                quadShaderData.Color = Float4::Zero;
+#else
                 quadShaderData.Color = Float4::One;
+#endif
                 context->UpdateCB(quadShaderCB, &quadShaderData);
                 context->BindCB(0, quadShaderCB);
 

Source/Shaders/ShadowsCommon.hlsl

@@ -72,6 +72,7 @@ float3 GetShadowPositionOffset(float offsetScale, float NoL, float3 normal)
 
 float CalculateSubsurfaceOcclusion(float opacity, float sceneDepth, float shadowMapDepth)
 {
+    // `sceneDepth` and `shadowMapDepth`are raw depths, so we have to flip them when reverse-z is enabled
 #if FLAX_REVERSE_Z
     float thickness = max(shadowMapDepth - sceneDepth, 0);
 #else

Source/Shaders/ShadowsSampling.hlsl

@@ -11,13 +11,27 @@
 #endif
 
 #if FEATURE_LEVEL >= FEATURE_LEVEL_SM5
+
+#if FLAX_REVERSE_Z
+#define SAMPLE_SHADOW_MAP(shadowMap, shadowUV, sceneDepth) (1 - shadowMap.SampleCmpLevelZero(ShadowSamplerLinear, shadowUV, sceneDepth))
+#define SAMPLE_SHADOW_MAP_OFFSET(shadowMap, shadowUV, texelOffset, sceneDepth) (1 - shadowMap.SampleCmpLevelZero(ShadowSamplerLinear, shadowUV, sceneDepth, texelOffset))
+#else
 #define SAMPLE_SHADOW_MAP(shadowMap, shadowUV, sceneDepth) shadowMap.SampleCmpLevelZero(ShadowSamplerLinear, shadowUV, sceneDepth)
 #define SAMPLE_SHADOW_MAP_OFFSET(shadowMap, shadowUV, texelOffset, sceneDepth) shadowMap.SampleCmpLevelZero(ShadowSamplerLinear, shadowUV, sceneDepth, texelOffset)
+#endif
+
+#else
+
+#if FLAX_REVERSE_Z
+#define SAMPLE_SHADOW_MAP(shadowMap, shadowUV, sceneDepth) (sceneDepth > shadowMap.SampleLevel(SamplerLinearClamp, shadowUV, 0).r)
+#define SAMPLE_SHADOW_MAP_OFFSET(shadowMap, shadowUV, texelOffset, sceneDepth) (sceneDepth > shadowMap.SampleLevel(SamplerLinearClamp, shadowUV, 0, texelOffset).r)
 #else
 #define SAMPLE_SHADOW_MAP(shadowMap, shadowUV, sceneDepth) (sceneDepth < shadowMap.SampleLevel(SamplerLinearClamp, shadowUV, 0).r)
 #define SAMPLE_SHADOW_MAP_OFFSET(shadowMap, shadowUV, texelOffset, sceneDepth) (sceneDepth < shadowMap.SampleLevel(SamplerLinearClamp, shadowUV, 0, texelOffset).r)
 #endif
 
+#endif
+
 float4 GetShadowMask(ShadowSample shadow)
 {
     return float4(shadow.SurfaceShadow, shadow.TransmissionShadow, 1, 1);
@@ -43,7 +57,11 @@ float2 GetLightShadowAtlasUV(ShadowData shadow, ShadowTileData shadowTile, float
 {
     // Project into shadow space (WorldToShadow is pre-multiplied to convert Clip Space to UV Space)
     shadowPosition = mul(float4(samplePosition, 1.0f), shadowTile.WorldToShadow);
+#if FLAX_REVERSE_Z
+    shadowPosition.z += shadow.Bias;
+#else
     shadowPosition.z -= shadow.Bias;
+#endif
     shadowPosition.xyz /= shadowPosition.w;
 
     // UV Space -> Atlas Tile UV Space