First draft of Warpmap Generation workgroup implementation

Author: kevyuu

include/nbl/builtin/hlsl/concepts/accessors/envmap.hlsl

@@ -0,0 +1,47 @@
+#ifndef _NBL_BUILTIN_HLSL_CONCEPTS_ACCESSORS_ENVMAP_INCLUDED_
+#define _NBL_BUILTIN_HLSL_CONCEPTS_ACCESSORS_ENVMAP_INCLUDED_
+
+#include "nbl/builtin/hlsl/concepts/accessors/generic_shared_data.hlsl"
+
+namespace nbl
+{
+namespace hlsl
+{
+namespace workgroup
+{
+namespace envmap
+{
+// declare concept
+#define NBL_CONCEPT_NAME LuminanceReadAccessor
+#define NBL_CONCEPT_TPLT_PRM_KINDS (typename)
+#define NBL_CONCEPT_TPLT_PRM_NAMES (U)
+// not the greatest syntax but works
+#define NBL_CONCEPT_PARAM_0 (a,U)
+#define NBL_CONCEPT_PARAM_1 (uv,uint32_t2)
+#define NBL_CONCEPT_PARAM_2 (level,uint32_t)
+#define NBL_CONCEPT_PARAM_3 (offset,uint32_t2)
+// start concept
+NBL_CONCEPT_BEGIN(4)
+// need to be defined AFTER the concept begins
+#define a NBL_CONCEPT_PARAM_T NBL_CONCEPT_PARAM_0
+#define uv NBL_CONCEPT_PARAM_T NBL_CONCEPT_PARAM_1
+#define level NBL_CONCEPT_PARAM_T NBL_CONCEPT_PARAM_2
+#define offset NBL_CONCEPT_PARAM_T NBL_CONCEPT_PARAM_3
+NBL_CONCEPT_END(
+    ((NBL_CONCEPT_REQ_EXPR_RET_TYPE)((a.template get(uv,level,offset)) , ::nbl::hlsl::is_same_v, float32_t4>))
+);
+#undef offset
+#undef level
+#undef uv
+#undef a
+#include <nbl/builtin/hlsl/concepts/__end.hlsl>
+
+template <typename T>
+NBL_BOOL_CONCEPT WarpmapWriteAccessor = concepts::accessors::GenericWriteAccessor<T, float32_t2, uint32_t2>;
+
+}
+}
+}
+}
+
+#endif

include/nbl/builtin/hlsl/workgroup/envmap.hlsl

@@ -0,0 +1,108 @@
+
+#ifndef _NBL_BUILTIN_HLSL_WORKGROUP_ENVMAP_IMPORTANCE_SAMPLING_INCLUDED_
+#define _NBL_BUILTIN_HLSL_WORKGROUP_ENVMAP_IMPORTANCE_SAMPLING_INCLUDED_
+
+namespace nbl
+{
+namespace hlsl
+{
+namespace workgroup
+{
+namespace envmap
+{
+namespace impl 
+{
+  bool choseSecond(float first, float second, NBL_REF_ARG(float) xi)
+  {
+    // numerical resilience against IEEE754
+    float firstProb = 1.0f / (1.0f + second / first);
+    float dummy = 0.0f;
+    return math::partitionRandVariable(firstProb, xi, dummy);
+  }
+
+}
+
+}
+}
+}
+}
+
+#ifdef __HLSL_VERSION
+namespace nbl
+{
+namespace hlsl
+{
+namespace workgroup
+{
+namespace envmap
+{
+
+struct WarpmapGeneration 
+{
+
+  template <typename LuminanceAccessor, typename OutputAccessor NBL_FUNC_REQUIRES (envmap::LuminanceReadAccessor<LuminanceAccessor> && envmap::WarpmapWriteAccessor<OutputAccessor>)
+  // TODO(kevinyu): Should lumapMapSize and warpMapSize provided by Accessor?
+  static void __call(NBL_CONST_REF_ARG(LuminanceAccessor) luminanceAccessor, NBL_REF_ARG(OutputAcessor) outputAccessor, uint32_t2 lumaMapSize, uint32_t2 warpMapSize)
+  {
+    const uint32_t threadID = uint32_t(SubgroupContiguousIndex());
+    const uint32_t lastWarpMapPixel = warpMapSize - uint32_t2(1, 1);
+
+    if (all(threadID < warpMapSize))
+    {
+      float32_t2 xi = float32_t2(threadID) / float32_t2(lastWarpMapPixel);
+
+      uint32_t2 p;
+      p.y = 0;
+
+      // TODO(kevinyu): Implement findMSB
+      const uint32_t2 mip2x1 = findMSB(lumaMapSize.x) - 1;
+		  // do one split in the X axis first cause penultimate full mip would have been 2x1
+      p.x = impl::choseSecond(luminanceAccessor.get(uint32_t2(0, 0), mip2x1, uint32_t2(0, 0)), luminanceAccessor.get(uint32_t2(0, 0), mip2x1, uint32_t2(1, 0), xi.x) ? 1 : 0;
+      for (uint32_t i = mip2x1; i != 0;)
+      {
+        --i;
+        p <<= 1;
+        const float32_t4 values = float32_t4(
+          luminanceAccessor.get(p, i, uint32_t2(0, 1)),
+          luminanceAccessor.get(p, i, uint32_t2(1, 1)),
+          luminanceAccessor.get(p, i, uint32_t2(1, 0)),
+          luminanceAccessor.get(p, i, uint32_t2(0, 0))
+        );
+
+        float32_t wx_0, wx_1;
+        {
+          const float32_t wy_0 = values[3] + values[2];
+          const float32_t wy_1 = values[1] + values[0];
+          if (impl::choseSecond(wy_0, wy_1, xi.y)) 
+          {
+            p.y |= 1;
+            wx_0 = values[0];
+            wx_1 = values[1];
+          }
+          else 
+          {
+            wx_0 = values[3];
+            wx_1 = values[2];
+          }
+        }
+         
+        if (impl::choseSecond(wx_0, wx_1, xi.x))
+        {
+          p.x |= 1;
+        }
+      }
+
+      const float32_t2 directionUV = (float32_t2(p.x, p.y) + xi) / float32_t2(lumaMapSize);
+      outputAccessor.set(threadID, directionUV);
+    }
+  }
+
+};
+
+}
+}
+}
+}
+#endif
+
+#endif