minor changes to rwmc usage

Author: keptsecret

include/nbl/builtin/hlsl/rwmc/CascadeAccumulator.hlsl

@@ -69,12 +69,9 @@ struct CascadeAccumulator
     // most of this code is stolen from https://cg.ivd.kit.edu/publications/2018/rwmc/tool/split.cpp
     void addSample(uint32_t sampleCount, input_sample_type _sample)
     {
-        const float32_t2 unpackedParams = hlsl::unpackHalf2x16(splattingParameters.packedLog2);
-        const cascade_layer_scalar_type log2Start = unpackedParams[0];
-        const cascade_layer_scalar_type log2Base = unpackedParams[1];
         const cascade_layer_scalar_type luma = getLuma(_sample);
         const cascade_layer_scalar_type log2Luma = log2<cascade_layer_scalar_type>(luma);
-        const cascade_layer_scalar_type cascade = log2Luma * 1.f / log2Base - log2Start / log2Base;
+        const cascade_layer_scalar_type cascade = log2Luma * splattingParameters.rcpLog2Base - splattingParameters.baseRootOfStart;
         const cascade_layer_scalar_type clampedCascade = clamp(cascade, 0, CascadeCount - 1);
         // c<=0 -> 0, c>=Count-1 -> Count-1 
         uint32_t lowerCascadeIndex = floor<cascade_layer_scalar_type>(cascade);
@@ -85,7 +82,11 @@ struct CascadeAccumulator
 
         // handle super bright sample case
         if (cascade > CascadeCount - 1)
+        {
+            const cascade_layer_scalar_type log2Base = cascade_layer_scalar_type(1.0) / splattingParameters.rcpLog2Base;
+            const cascade_layer_scalar_type log2Start = splattingParameters.baseRootOfStart * log2Base;
             lowerCascadeWeight = exp2(log2Start + log2Base * (CascadeCount - 1) - log2Luma);
+        }
 
         accumulation.addSampleIntoCascadeEntry(_sample, lowerCascadeIndex, lowerCascadeWeight, higherCascadeWeight, sampleCount);
     }

include/nbl/builtin/hlsl/rwmc/SplattingParameters.hlsl

@@ -2,6 +2,7 @@
 #define _NBL_BUILTIN_HLSL_RWMC_SPLATTING_PARAMETERS_HLSL_INCLUDED_
 
 #include "nbl/builtin/hlsl/cpp_compat.hlsl"
+#include "nbl/builtin/hlsl/tgmath.hlsl"
 
 namespace nbl
 {
@@ -12,10 +13,18 @@ namespace rwmc
 
 struct SplattingParameters
 {
-    // float16_t log2Start; 0
-    // float16_t log2Base; 1
-    // pack as Half2x16
-    int32_t packedLog2;
+    using scalar_t = float;
+
+    static SplattingParameters create(const scalar_t base, const scalar_t start)
+    {
+        SplattingParameters retval;
+        retval.rcpLog2Base = scalar_t(1.0) / hlsl::log2(base);
+        retval.baseRootOfStart = hlsl::log2(start) * retval.rcpLog2Base;
+        return retval;
+    }
+   
+    scalar_t baseRootOfStart;
+    scalar_t rcpLog2Base;
 };
 
 }