public unsafe AccelerationStructureBuffers CreateTopLevelAS(ID3D12Device5 pDevice, ID3D12GraphicsCommandList4 pCmdList, AccelerationStructureBuffers[] pBottomLevelAS, ref long tlasSize)
{
int instances = 2;
// First, get the size of the TLAS buffers and create them
BuildRaytracingAccelerationStructureInputs inputs = new BuildRaytracingAccelerationStructureInputs();
inputs.Layout = ElementsLayout.Array;
inputs.Flags = RaytracingAccelerationStructureBuildFlags.None;
inputs.DescriptorsCount = instances;
inputs.Type = RaytracingAccelerationStructureType.TopLevel;
RaytracingAccelerationStructurePrebuildInfo info;
info = pDevice.GetRaytracingAccelerationStructurePrebuildInfo(inputs);
// Create the buffers
AccelerationStructureBuffers buffers = new AccelerationStructureBuffers();
buffers.pScratch = this.CreateBuffer(pDevice, (uint)info.ScratchDataSizeInBytes, ResourceFlags.AllowUnorderedAccess, ResourceStates.UnorderedAccess, kDefaultHeapProps);
buffers.pResult = this.CreateBuffer(pDevice, (uint)info.ResultDataMaxSizeInBytes, ResourceFlags.AllowUnorderedAccess, ResourceStates.RaytracingAccelerationStructure, kDefaultHeapProps);
tlasSize = info.ResultDataMaxSizeInBytes;
// The instance desc should be inside a buffer, create and map the buffer
buffers.pInstanceDesc = this.CreateBuffer(pDevice, (uint)(Unsafe.SizeOf <FixedRaytracingInstanceDescription>() * instances), ResourceFlags.None, ResourceStates.GenericRead, kUploadHeapProps);
FixedRaytracingInstanceDescription[] pInstanceDesc = new FixedRaytracingInstanceDescription[instances];
// The transformation matrices for the instances
Matrix4x4[] transformation = new Matrix4x4[instances];
transformation[0] = Matrix4x4.CreateTranslation(new Vector3(0, -1.0f, 0));
transformation[1] = Matrix4x4.CreateScale(2.0f);
pInstanceDesc[0].InstanceID = 0; // This value will be exposed to the shader via InstanceID()
pInstanceDesc[0].InstanceContributionToHitGroupIndex = 0; // This is the offset inside the shader-table. We only have a single geometry, so the offset 0
pInstanceDesc[0].Flags = (byte)RaytracingInstanceFlags.None;
pInstanceDesc[0].Transform = Matrix4x4.Transpose(transformation[0]).ToMatrix3x4(); // GLM is column major, the INSTANCE_DESC is row major
pInstanceDesc[0].AccelerationStructure = pBottomLevelAS[0].pResult.GPUVirtualAddress;
pInstanceDesc[0].InstanceMask = 0xff;
for (int i = 1; i < instances; i++)
{
pInstanceDesc[i].InstanceID = i; // This value will be exposed to the shader via InstanceID()
pInstanceDesc[i].InstanceContributionToHitGroupIndex = 0; // This is the offset inside the shader-table. We only have a single geometry, so the offset 0
pInstanceDesc[i].Flags = (byte)RaytracingInstanceFlags.None;
pInstanceDesc[i].Transform = Matrix4x4.Transpose(transformation[i]).ToMatrix3x4(); // GLM is column major, the INSTANCE_DESC is row major
pInstanceDesc[i].AccelerationStructure = pBottomLevelAS[1].pResult.GPUVirtualAddress;
pInstanceDesc[i].InstanceMask = 0xff;
}
IntPtr data;
data = buffers.pInstanceDesc.Map(0, null);
Helpers.MemCpy(data, pInstanceDesc, (uint)(Unsafe.SizeOf <FixedRaytracingInstanceDescription>() * instances));
buffers.pInstanceDesc.Unmap(0, null);
// Create the TLAS
BuildRaytracingAccelerationStructureDescription asDesc = new BuildRaytracingAccelerationStructureDescription();
asDesc.Inputs = inputs;
asDesc.Inputs.InstanceDescriptions = buffers.pInstanceDesc.GPUVirtualAddress;
asDesc.DestinationAccelerationStructureData = buffers.pResult.GPUVirtualAddress;
asDesc.ScratchAccelerationStructureData = buffers.pScratch.GPUVirtualAddress;
pCmdList.BuildRaytracingAccelerationStructure(asDesc);
// We need to insert a UAV barrier before using the acceleration structures in a raytracing operation
ResourceBarrier uavBarrier = new ResourceBarrier(new ResourceUnorderedAccessViewBarrier(buffers.pResult));
pCmdList.ResourceBarrier(uavBarrier);
return(buffers);
}
public unsafe AccelerationStructureBuffers BuildTopLevelAS(ID3D12Device5 pDevice, ID3D12GraphicsCommandList4 pCmdList, ID3D12Resource[] pBottomLevelAS, ref long tlasSize, float rotation, bool update, ref AccelerationStructureBuffers buffers)
{
// First, get the size of the TLAS buffers and create them
BuildRaytracingAccelerationStructureInputs inputs = new BuildRaytracingAccelerationStructureInputs();
inputs.Layout = ElementsLayout.Array;
inputs.Flags = RaytracingAccelerationStructureBuildFlags.AllowUpdate;
inputs.DescriptorsCount = 3; // NumDescs
inputs.Type = RaytracingAccelerationStructureType.TopLevel;
RaytracingAccelerationStructurePrebuildInfo info;
info = pDevice.GetRaytracingAccelerationStructurePrebuildInfo(inputs);
if (update)
{
// If this a request for an update, then the TLAS was already used in a DispatchRay() call. We need a UAV barrier to make sure the read operation ends before updating the buffer
ResourceBarrier uavBarrier1 = new ResourceBarrier(new ResourceUnorderedAccessViewBarrier(buffers.pResult));
pCmdList.ResourceBarrier(uavBarrier1);
}
else
{
buffers.pScratch = this.CreateBuffer(pDevice, (uint)info.ScratchDataSizeInBytes, ResourceFlags.AllowUnorderedAccess, ResourceStates.UnorderedAccess, kDefaultHeapProps);
buffers.pResult = this.CreateBuffer(pDevice, (uint)info.ResultDataMaxSizeInBytes, ResourceFlags.AllowUnorderedAccess, ResourceStates.RaytracingAccelerationStructure, kDefaultHeapProps);
buffers.pInstanceDesc = this.CreateBuffer(pDevice, (uint)Unsafe.SizeOf <FixedRaytracingInstanceDescription>() * 3, ResourceFlags.None, ResourceStates.GenericRead, kUploadHeapProps);
tlasSize = info.ResultDataMaxSizeInBytes;
}
FixedRaytracingInstanceDescription[] instanceDescs = new FixedRaytracingInstanceDescription[3];
// The transformation matrices for the instances
Matrix4x4[] transformation = new Matrix4x4[3];
Matrix4x4 rotationMat = Matrix4x4.CreateRotationY(rotation);
transformation[0] = Matrix4x4.Identity;
transformation[1] = rotationMat * Matrix4x4.CreateTranslation(new Vector3(-2, 0, 0));
transformation[2] = rotationMat * Matrix4x4.CreateTranslation(new Vector3(2, 0, 0));
// The InstanceContributionToHitGroupIndex is set based on the shader-table layout specified in createShaderTable()
// Create the desc for the triangle/plane instance
instanceDescs[0].InstanceID = 0;
instanceDescs[0].InstanceContributionToHitGroupIndex = 0;
instanceDescs[0].Flags = (byte)RaytracingInstanceFlags.None;
instanceDescs[0].Transform = Matrix4x4.Transpose(transformation[0]).ToMatrix3x4(); // GLM is column major, the INSTANCE_DESC is row major
instanceDescs[0].AccelerationStructure = pBottomLevelAS[0].GPUVirtualAddress;
instanceDescs[0].InstanceMask = 0xFF;
for (int i = 1; i < 3; i++)
{
instanceDescs[i].InstanceID = i; // This value will be exposed to the shader via InstanceID()
instanceDescs[i].InstanceContributionToHitGroupIndex = (i * 2) + 2; // The plane takes an additional entry in the shader-table, hence the +1
instanceDescs[i].Flags = (byte)RaytracingInstanceFlags.None;
instanceDescs[i].Transform = Matrix4x4.Transpose(transformation[i]).ToMatrix3x4(); // GLM is column major, the INSTANCE_DESC is row major
instanceDescs[i].AccelerationStructure = pBottomLevelAS[1].GPUVirtualAddress;
instanceDescs[i].InstanceMask = 0xFF;
}
// Map the instance desc buffer
IntPtr data;
data = buffers.pInstanceDesc.Map(0, null);
Helpers.MemCpy(data, instanceDescs, (uint)Unsafe.SizeOf <FixedRaytracingInstanceDescription>() * 3);
buffers.pInstanceDesc.Unmap(0, null);
// Create the TLAS
BuildRaytracingAccelerationStructureDescription asDesc = new BuildRaytracingAccelerationStructureDescription();
asDesc.Inputs = inputs;
asDesc.Inputs.InstanceDescriptions = buffers.pInstanceDesc.GPUVirtualAddress;
asDesc.DestinationAccelerationStructureData = buffers.pResult.GPUVirtualAddress;
asDesc.ScratchAccelerationStructureData = buffers.pScratch.GPUVirtualAddress;
// If this is an update operation, set the source buffer and the perform_update flag
if (update)
{
asDesc.Inputs.Flags |= RaytracingAccelerationStructureBuildFlags.PerformUpdate;
asDesc.SourceAccelerationStructureData = buffers.pResult.GPUVirtualAddress;
}
pCmdList.BuildRaytracingAccelerationStructure(asDesc);
// We need to insert a UAV barrier before using the acceleration structures in a raytracing operation
ResourceBarrier uavBarrier = new ResourceBarrier(new ResourceUnorderedAccessViewBarrier(buffers.pResult));
pCmdList.ResourceBarrier(uavBarrier);
return(buffers);
}
