CmdCreateTLAS()

void Spices::VulkanRayTracing::CmdCreateTLAS	(	VkCommandBuffer	cmdBuf,
		uint32_t	countInstance,
		VkDeviceAddress	instBufferAddr,
		std::unique_ptr< VulkanBuffer > &	scratchBuffer,
		VkBuildAccelerationStructureFlagsKHR	flags,
		bool	update,
		bool	motion )

Low level of Tlas creation. Creating the TLAS, called by buildTlas.

Parameters

[in]	cmdBuf	VkCommandBuffer.
[in]	countInstance	number of instances.
[in]	instBufferAddr	Buffer address of instances.
[in]	scratchBuffer	ScratchBuffer Buffer.
[in]	flags	Build creation flag.
[in]	update	Update == animation.
[in]	motion	Motion Blur.

Wraps a device pointer to the above uploaded instances.

Put the above into a VkAccelerationStructureGeometryKHR.We need to put the instances struct in a union and label it as instance data.

Find sizes.

Create TLAS.

Allocate the scratch memory.

Update build information.

Build Offsets info : n instances.

Build the TLAS.

Wraps a device pointer to the above uploaded instances.

Put the above into a VkAccelerationStructureGeometryKHR.We need to put the instances struct in a union and label it as instance data.

Find sizes.

Create TLAS.

Allocate the scratch memory.

Update build information.

Build Offsets info : n instances.

Build the TLAS.

Definition at line 229 of file VulkanRayTracing.cpp.

    {
        SPICES_PROFILE_ZONE;
 
        VkAccelerationStructureGeometryInstancesDataKHR instancesVk{};
        instancesVk.sType                          = VK_STRUCTURE_TYPE_ACCELERATION_STRUCTURE_GEOMETRY_INSTANCES_DATA_KHR;
        instancesVk.data.deviceAddress             = instBufferAddr;
 
        VkAccelerationStructureGeometryKHR topASGeometry{};
        topASGeometry.sType                        = VK_STRUCTURE_TYPE_ACCELERATION_STRUCTURE_GEOMETRY_KHR;
        topASGeometry.geometryType                 = VK_GEOMETRY_TYPE_INSTANCES_KHR;
        topASGeometry.geometry.instances           = instancesVk;
 
        VkAccelerationStructureBuildGeometryInfoKHR buildInfo{};
        buildInfo.sType                            = VK_STRUCTURE_TYPE_ACCELERATION_STRUCTURE_BUILD_GEOMETRY_INFO_KHR;
        buildInfo.flags                            = flags;
        buildInfo.geometryCount                    = 1;
        buildInfo.pGeometries                      = &topASGeometry;
        buildInfo.mode                             = update ? VK_BUILD_ACCELERATION_STRUCTURE_MODE_UPDATE_KHR : VK_BUILD_ACCELERATION_STRUCTURE_MODE_BUILD_KHR;
        buildInfo.type                             = VK_ACCELERATION_STRUCTURE_TYPE_TOP_LEVEL_KHR;
        buildInfo.srcAccelerationStructure         = VK_NULL_HANDLE;
 
        VkAccelerationStructureBuildSizesInfoKHR sizeInfo{};
        sizeInfo.sType                             = VK_STRUCTURE_TYPE_ACCELERATION_STRUCTURE_BUILD_SIZES_INFO_KHR;
 
        m_VulkanState.m_VkFunc.vkGetAccelerationStructureBuildSizesKHR(
            m_VulkanState.m_Device, 
            VK_ACCELERATION_STRUCTURE_BUILD_TYPE_DEVICE_KHR, 
            &buildInfo,
            &countInstance, 
            &sizeInfo
        );
 
#ifdef VK_NV_ray_tracing_motion_blur
 
        VkAccelerationStructureMotionInfoNV motionInfo{};
        motionInfo.sType                           = VK_STRUCTURE_TYPE_ACCELERATION_STRUCTURE_MOTION_INFO_NV;
        motionInfo.maxInstances                    = countInstance;
 
#endif
 
        if (update == false)
        {
            VkAccelerationStructureCreateInfoKHR createInfo{};
            createInfo.sType                       = VK_STRUCTURE_TYPE_ACCELERATION_STRUCTURE_CREATE_INFO_KHR;
            createInfo.type                        = VK_ACCELERATION_STRUCTURE_TYPE_TOP_LEVEL_KHR;
            createInfo.size                        = sizeInfo.accelerationStructureSize;
 
#ifdef VK_NV_ray_tracing_motion_blur
 
            if (motion)
            {
                createInfo.createFlags             = VK_ACCELERATION_STRUCTURE_CREATE_MOTION_BIT_NV;
                createInfo.pNext                   = &motionInfo;
            }
 
#endif
 
            m_tlas = CreateAcceleration(createInfo);
        }
 
        scratchBuffer = std::make_unique<VulkanBuffer>(
            m_VulkanState,
            "ScratchBuffer",
            sizeInfo.buildScratchSize,
            VK_BUFFER_USAGE_STORAGE_BUFFER_BIT |
            VK_BUFFER_USAGE_SHADER_DEVICE_ADDRESS_BIT,
            VMA_MEMORY_PROPERTY_DEDICATED_MEMORY_BIT
        );
 
        VkDeviceAddress scratchAddress = scratchBuffer->GetAddress();
 
        buildInfo.srcAccelerationStructure         = update ? m_tlas.accel->Get() : VK_NULL_HANDLE;
        buildInfo.dstAccelerationStructure         = m_tlas.accel->Get();
        buildInfo.scratchData.deviceAddress        = scratchAddress;
 
        VkAccelerationStructureBuildRangeInfoKHR buildOffsetInfo{};
        buildOffsetInfo.primitiveCount             = countInstance;
        buildOffsetInfo.primitiveOffset            = 0; 
        buildOffsetInfo.firstVertex                = 0;
        buildOffsetInfo.transformOffset            = 0;
 
        const VkAccelerationStructureBuildRangeInfoKHR* pBuildOffsetInfo = &buildOffsetInfo;
 
        m_VulkanState.m_VkFunc.vkCmdBuildAccelerationStructuresKHR(cmdBuf, 1, &buildInfo, &pBuildOffsetInfo);
    }