From fedfff191e9d40955b2b1756becaf03a9ade0526 Mon Sep 17 00:00:00 2001
From: myT <>
Date: Wed, 7 Feb 2024 00:40:20 +0100
Subject: [PATCH] minimizing memory allocations in CmdCreateBLAS

---
 code/renderer/rhi_d3d12.cpp | 23 +++++++++++++++--------
 1 file changed, 15 insertions(+), 8 deletions(-)

diff --git a/code/renderer/rhi_d3d12.cpp b/code/renderer/rhi_d3d12.cpp
index aaa07ff..e060db3 100644
--- a/code/renderer/rhi_d3d12.cpp
+++ b/code/renderer/rhi_d3d12.cpp
@@ -752,6 +752,8 @@ namespace RHI
 		HBuffer raytracingScratchBuffer;
 		HBuffer raytracingInstanceBuffer;
 		uint32_t beginFrameCounter;
+		D3D12_RAYTRACING_GEOMETRY_DESC* rtGeoDescs;
+		uint32_t rtGeoDescCount;
 
 		// immediate-mode barrier API
 		TextureBarrier textureBarriers[64];
@@ -3687,6 +3689,8 @@ namespace RHI
 			CloseHandle(rhi.frameLatencyWaitableObject);
 		}
 
+		free(rhi.rtGeoDescs);
+
 		rhi.upload.Release();
 		rhi.readback.Release();
 		rhi.mainFence.Release();
@@ -5521,17 +5525,22 @@ namespace RHI
 		const D3D12_GPU_VIRTUAL_ADDRESS baseVertexAddress = rhi.buffers.Get(rhiDesc.vertexBuffer).gpuAddress;
 		const D3D12_GPU_VIRTUAL_ADDRESS baseIndexAddress = rhi.buffers.Get(rhiDesc.indexBuffer).gpuAddress;
 
-		D3D12_RAYTRACING_GEOMETRY_DESC* const geos =
-			(D3D12_RAYTRACING_GEOMETRY_DESC*)calloc(rhiDesc.meshCount, sizeof(D3D12_RAYTRACING_GEOMETRY_DESC));
-		if(geos == NULL)
+		if(rhiDesc.meshCount > rhi.rtGeoDescCount)
 		{
-			ri.Error(ERR_FATAL, "Failed to allocate %d D3D12_RAYTRACING_GEOMETRY_DESC instances\n", (int)rhiDesc.meshCount);
+			const uint32_t meshCount = max(rhiDesc.meshCount, 2 * rhi.rtGeoDescCount);
+			const size_t byteCount = meshCount * sizeof(D3D12_RAYTRACING_GEOMETRY_DESC);
+			rhi.rtGeoDescs = (D3D12_RAYTRACING_GEOMETRY_DESC*)realloc(rhi.rtGeoDescs, byteCount);
+			if(rhi.rtGeoDescs == NULL)
+			{
+				ri.Error(ERR_FATAL, "Failed to allocate %d D3D12_RAYTRACING_GEOMETRY_DESC instances\n", (int)meshCount);
+			}
+			rhi.rtGeoDescCount = rhiDesc.meshCount;
 		}
 
 		for(uint32_t i = 0; i < rhiDesc.meshCount; ++i)
 		{
 			const BLASMeshDesc& mesh = rhiDesc.meshes[i];
-			D3D12_RAYTRACING_GEOMETRY_DESC& geoDesc = geos[i];
+			D3D12_RAYTRACING_GEOMETRY_DESC& geoDesc = rhi.rtGeoDescs[i];
 			geoDesc.Type = D3D12_RAYTRACING_GEOMETRY_TYPE_TRIANGLES;
 			geoDesc.Flags = mesh.isFullyOpaque ?
 				D3D12_RAYTRACING_GEOMETRY_FLAG_OPAQUE :
@@ -5551,7 +5560,7 @@ namespace RHI
 		inputs.Flags = D3D12_RAYTRACING_ACCELERATION_STRUCTURE_BUILD_FLAG_NONE;
 		inputs.DescsLayout = D3D12_ELEMENTS_LAYOUT_ARRAY;
 		inputs.NumDescs = rhiDesc.meshCount;
-		inputs.pGeometryDescs = geos;
+		inputs.pGeometryDescs = rhi.rtGeoDescs;
 		
 		D3D12_RAYTRACING_ACCELERATION_STRUCTURE_PREBUILD_INFO info = {};
 		rhi.device->GetRaytracingAccelerationStructurePrebuildInfo(&inputs, &info);
@@ -5574,8 +5583,6 @@ namespace RHI
 		rtasDesc.Inputs = inputs;
 		rhi.commandList->BuildRaytracingAccelerationStructure(&rtasDesc, 0, NULL);
 
-		free(geos);
-
 		CmdBeginBarrier();
 		CmdBufferBarrier(*blasBuffer, ResourceStates::UnorderedAccessBit);
 		CmdEndBarrier();