614 lines
24 KiB
HTML
614 lines
24 KiB
HTML
<meta charset="utf-8" lang="en">
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**NVIDIA Vulkan Ray Tracing Tutorial**
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**Animation**
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<small>Authors: [Martin-Karl Lefrançois](https://devblogs.nvidia.com/author/mlefrancois/), Neil Bickford </small>
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# Animation
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This is an extension of the [Vulkan ray tracing tutorial](vkrt_tutorial.md.html).
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We will discuss two animation methods: animating only the transformation matrices, and animating the geometry itself.
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(insert setup.md.html here)
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# Animating the Matrices
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This first example shows how we can update the matrices used for instances in the TLAS.
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## Creating a Scene
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In main.cpp we can create a new scene with a ground plane and 21 instances of the Wuson model, by replacing the
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`helloVk.loadModel` calls in `main()`. The code below creates all of the instances
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at the same position, but we will displace them later in the animation function. If you run the example,
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you will find that the rendering is considerably slow, because the geometries are exactly at the same position
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and the acceleration structure does not deal with this well.
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~~~~ C++
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helloVk.loadModel(nvh::findFile("media/scenes/plane.obj", defaultSearchPaths),
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nvmath::scale_mat4(nvmath::vec3f(2.f, 1.f, 2.f)));
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helloVk.loadModel(nvh::findFile("media/scenes/wuson.obj", defaultSearchPaths));
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HelloVulkan::ObjInstance inst = helloVk.m_objInstance.back();
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for(int i = 0; i < 20; i++)
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helloVk.m_objInstance.push_back(inst);
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~~~~
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## Animation Function
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We want to have all of the Wuson models running in a circle, and we will first modify the rasterizer to handle this.
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Animating the transformation matrices will be done entirely on the CPU, and we will copy the computed transformation to the GPU.
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In the next example, the animation will be done on the GPU using a compute shader.
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Add the declaration of the animation to the `HelloVulkan` class.
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~~~~ C++
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void animationInstances(float time);
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~~~~
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The first part computes the transformations for all of the Wuson models, placing each one behind another.
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~~~~ C++
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void HelloVulkan::animationInstances(float time)
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{
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const int32_t nbWuson = static_cast<int32_t>(m_objInstance.size() - 1);
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const float deltaAngle = 6.28318530718f / static_cast<float>(nbWuson);
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const float wusonLength = 3.f;
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const float radius = wusonLength / (2.f * sin(deltaAngle / 2.0f));
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const float offset = time * 0.5f;
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for(int i = 0; i < nbWuson; i++)
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{
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int wusonIdx = i + 1;
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ObjInstance& inst = m_objInstance[wusonIdx];
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inst.transform = nvmath::rotation_mat4_y(i * deltaAngle + offset)
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* nvmath::translation_mat4(radius, 0.f, 0.f);
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inst.transformIT = nvmath::transpose(nvmath::invert(inst.transform));
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}
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~~~~
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Next, we update the buffer that describes the scene, which is used by the rasterizer to set each object's position, and also by the ray tracer to compute shading normals.
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~~~~ C++
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// Update the buffer
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vk::DeviceSize bufferSize = m_objInstance.size() * sizeof(ObjInstance);
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nvvkBuffer stagingBuffer = m_alloc.createBuffer(bufferSize, vk::BufferUsageFlagBits::eTransferSrc,
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vk::MemoryPropertyFlagBits::eHostVisible);
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// Copy data to staging buffer
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auto* gInst = m_alloc.map(stagingBuffer);
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memcpy(gInst, m_objInstance.data(), bufferSize);
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m_alloc.unmap(stagingBuffer);
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// Copy staging buffer to the Scene Description buffer
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nvvk::CommandPool genCmdBuf(m_device, m_graphicsQueueIndex);
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vk::CommandBuffer cmdBuf = genCmdBuf.createCommandBuffer();
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cmdBuf.copyBuffer(stagingBuffer.buffer, m_sceneDesc.buffer, vk::BufferCopy(0, 0, bufferSize));
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m_debug.endLabel(cmdBuf);
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genCmdBuf.submitAndWait(cmdBuf);
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m_alloc.destroy(stagingBuffer);
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m_rtBuilder.updateTlasMatrices(m_tlas);
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m_rtBuilder.updateBlas(2);
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}
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~~~~
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<script type="preformatted">
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!!! Note:
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We could have used `cmdBuf.updateBuffer<ObjInstance>(m_sceneDesc.buffer, 0, m_objInstance)` to
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update the buffer, but this function only works for buffers with less than 65,536 bytes. If we had 2000 Wuson models, this
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call wouldn't work.
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## Loop Animation
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In `main()`, just before the main loop, add a variable to hold the start time.
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We will use this time in our animation function.
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~~~~ C++
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auto start = std::chrono::system_clock::now();
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~~~~
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Inside the `while` loop, just before calling `appBase.prepareFrame()`, invoke the animation function.
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~~~~ C++
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std::chrono::duration<float> diff = std::chrono::system_clock::now() - start;
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helloVk.animationInstances(diff.count());
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~~~~
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If you run the application, the Wuson models will be running in a circle when using the rasterizer, but
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they will still be at their original positions in the ray traced version. We will need to update the TLAS for this.
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# Update TLAS
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Since we want to update the transformation matrices in the TLAS, we need to keep some of the objects used to create it.
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First, move the vector of `nvvk::RaytracingBuilder::Instance` objects from `HelloVulkan::createTopLevelAS()` to the
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`HelloVulkan` class.
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~~~~ C++
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std::vector<nvvk::RaytracingBuilder::Instance> m_tlas;
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~~~~
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Make sure to rename it to `m_tlas`, instead of `tlas`.
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One important point is that we need to set the TLAS build flags to allow updates, by adding the`vk::BuildAccelerationStructureFlagBitsKHR::eAllowUpdate` flag.
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This is absolutely needed, since otherwise the TLAS cannot be updated.
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~~~~ C++
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void HelloVulkan::createTopLevelAS()
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{
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m_tlas.reserve(m_objInstance.size());
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for(int i = 0; i < static_cast<int>(m_objInstance.size()); i++)
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{
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nvvk::RaytracingBuilder::Instance rayInst;
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rayInst.transform = m_objInstance[i].transform; // Position of the instance
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rayInst.instanceCustomId = i; // gl_InstanceCustomIndexEXT
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rayInst.blasId = m_objInstance[i].objIndex;
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rayInst.hitGroupId = m_objInstance[i].hitgroup;
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rayInst.flags = VK_GEOMETRY_INSTANCE_TRIANGLE_CULL_DISABLE_BIT_NV;
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m_tlas.emplace_back(rayInst);
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}
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m_rtBuilder.buildTlas(m_tlas, vk::BuildAccelerationStructureFlagBitsKHR::ePreferFastTrace
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| vk::BuildAccelerationStructureFlagBitsKHR::eAllowUpdate);
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}
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~~~~
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Back in `HelloVulkan::animationInstances()`, we need to copy the new computed transformation
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matrices to the vector of `nvvk::RaytracingBuilder::Instance` objects.
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In the `for` loop, add at the end
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~~~~ C++
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nvvk::RaytracingBuilder::Instance& tinst = m_tlas[wusonIdx];
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tinst.transform = inst.transform;
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~~~~
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The last point is to call the update at the end of the function.
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~~~~ C++
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m_rtBuilder.updateTlasMatrices(m_tlas);
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~~~~
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## nvvk::RaytracingBuilder::updateTlasMatrices (Implementation)
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We currently use `nvvk::RaytracingBuilder` to update the matrices for convenience, but
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this could be done more efficiently if one kept some of the buffer and memory references. Using a
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memory allocator, such as the one described in the [Many Objects Tutorial](vkrt_tuto_instances.md.html),
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could also be an alternative for avoiding multiple reallocations. Here's the implementation of `nvvk::RaytracingBuilder::updateTlasMatrices`.
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### Staging Buffer
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As in the rasterizer, the data needs to be staged before it can be copied to the buffer used for
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building the TLAS.
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~~~~ C++
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void updateTlasMatrices(const std::vector<Instance>& instances)
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{
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VkDeviceSize bufferSize = instances.size() * sizeof(VkAccelerationStructureInstanceKHR);
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// Create a staging buffer on the host to upload the new instance data
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nvvkBuffer stagingBuffer = m_alloc.createBuffer(bufferSize, VK_BUFFER_USAGE_TRANSFER_SRC_BIT,
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#if defined(ALLOC_VMA)
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VmaMemoryUsage::VMA_MEMORY_USAGE_CPU_TO_GPU
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#else
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VK_MEMORY_PROPERTY_HOST_VISIBLE_BIT | VK_MEMORY_PROPERTY_HOST_COHERENT_BIT
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#endif
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);
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// Copy the instance data into the staging buffer
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auto* gInst = reinterpret_cast<VkAccelerationStructureInstanceKHR*>(m_alloc.map(stagingBuffer));
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for(int i = 0; i < instances.size(); i++)
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{
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gInst[i] = instanceToVkGeometryInstanceKHR(instances[i]);
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}
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m_alloc.unmap(stagingBuffer);
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~~~~
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### Scratch Memory
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Building the TLAS always needs scratch memory, and so we need to request it. If
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we hadn't set the `eAllowUpdate` flag, the returned size would be zero and the rest of the code
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would fail.
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~~~~ C++
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// Compute the amount of scratch memory required by the AS builder to update
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VkAccelerationStructureMemoryRequirementsInfoKHR memoryRequirementsInfo{
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VK_STRUCTURE_TYPE_ACCELERATION_STRUCTURE_MEMORY_REQUIREMENTS_INFO_KHR};
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memoryRequirementsInfo.type = VK_ACCELERATION_STRUCTURE_MEMORY_REQUIREMENTS_TYPE_UPDATE_SCRATCH_KHR;
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memoryRequirementsInfo.accelerationStructure = m_tlas.as.accel;
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memoryRequirementsInfo.buildType = VK_ACCELERATION_STRUCTURE_BUILD_TYPE_DEVICE_KHR;
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VkMemoryRequirements2 reqMem{VK_STRUCTURE_TYPE_MEMORY_REQUIREMENTS_2};
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vkGetAccelerationStructureMemoryRequirementsKHR(m_device, &memoryRequirementsInfo, &reqMem);
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VkDeviceSize scratchSize = reqMem.memoryRequirements.size;
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// Allocate the scratch buffer
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nvvkBuffer scratchBuffer =
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m_alloc.createBuffer(scratchSize, VK_BUFFER_USAGE_RAY_TRACING_BIT_KHR | VK_BUFFER_USAGE_SHADER_DEVICE_ADDRESS_BIT);
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VkBufferDeviceAddressInfo bufferInfo{VK_STRUCTURE_TYPE_BUFFER_DEVICE_ADDRESS_INFO};
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bufferInfo.buffer = scratchBuffer.buffer;
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VkDeviceAddress scratchAddress = vkGetBufferDeviceAddress(m_device, &bufferInfo);
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~~~~
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### Update the Buffer
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In a new command buffer, we copy the staging buffer to the device buffer and
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add a barrier to make sure the memory finishes copying before updating the TLAS.
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~~~~ C++
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// Update the instance buffer on the device side and build the TLAS
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nvvk::CommandPool genCmdBuf(m_device, m_queueIndex);
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VkCommandBuffer cmdBuf = genCmdBuf.createCommandBuffer();
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VkBufferCopy region{0, 0, bufferSize};
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vkCmdCopyBuffer(cmdBuf, stagingBuffer.buffer, m_instBuffer.buffer, 1, ®ion);
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//VkBufferDeviceAddressInfo bufferInfo{VK_STRUCTURE_TYPE_BUFFER_DEVICE_ADDRESS_INFO};
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bufferInfo.buffer = m_instBuffer.buffer;
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VkDeviceAddress instanceAddress = vkGetBufferDeviceAddress(m_device, &bufferInfo);
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// Make sure the copy of the instance buffer are copied before triggering the
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// acceleration structure build
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VkMemoryBarrier barrier{VK_STRUCTURE_TYPE_MEMORY_BARRIER};
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barrier.srcAccessMask = VK_ACCESS_TRANSFER_WRITE_BIT;
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barrier.dstAccessMask = VK_ACCESS_ACCELERATION_STRUCTURE_WRITE_BIT_KHR;
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vkCmdPipelineBarrier(cmdBuf, VK_PIPELINE_STAGE_TRANSFER_BIT, VK_PIPELINE_STAGE_ACCELERATION_STRUCTURE_BUILD_BIT_KHR,
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0, 1, &barrier, 0, nullptr, 0, nullptr);
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~~~~
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### Update Acceleration Structure
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We update the TLAS using the same acceleration structure for source and
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destination to update it in place, and using the VK_TRUE parameter to trigger the update.
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~~~~ C++
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VkAccelerationStructureGeometryDataKHR geometry{VK_STRUCTURE_TYPE_ACCELERATION_STRUCTURE_GEOMETRY_INSTANCES_DATA_KHR};
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geometry.instances.arrayOfPointers = VK_FALSE;
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geometry.instances.data.deviceAddress = instanceAddress;
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VkAccelerationStructureGeometryKHR topASGeometry{VK_STRUCTURE_TYPE_ACCELERATION_STRUCTURE_GEOMETRY_KHR};
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topASGeometry.geometryType = VK_GEOMETRY_TYPE_INSTANCES_KHR;
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topASGeometry.geometry = geometry;
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const VkAccelerationStructureGeometryKHR* pGeometry = &topASGeometry;
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VkAccelerationStructureBuildGeometryInfoKHR topASInfo{VK_STRUCTURE_TYPE_ACCELERATION_STRUCTURE_BUILD_GEOMETRY_INFO_KHR};
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topASInfo.flags = m_tlas.flags;
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topASInfo.update = VK_TRUE;
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topASInfo.srcAccelerationStructure = m_tlas.as.accel;
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topASInfo.dstAccelerationStructure = m_tlas.as.accel;
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topASInfo.geometryArrayOfPointers = VK_FALSE;
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topASInfo.geometryCount = 1;
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topASInfo.ppGeometries = &pGeometry;
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topASInfo.scratchData.deviceAddress = scratchAddress;
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uint32_t nbInstances = (uint32_t)instances.size();
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VkAccelerationStructureBuildOffsetInfoKHR buildOffsetInfo = {nbInstances, 0, 0, 0};
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const VkAccelerationStructureBuildOffsetInfoKHR* pBuildOffsetInfo = &buildOffsetInfo;
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// Build the TLAS
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// Update the acceleration structure. Note the VK_TRUE parameter to trigger the update,
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// and the existing TLAS being passed and updated in place
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vkCmdBuildAccelerationStructureKHR(cmdBuf, 1, &topASInfo, &pBuildOffsetInfo);
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genCmdBuf.submitAndWait(cmdBuf);
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~~~~
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### Cleanup
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Finally, we release all temporary buffers.
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~~~~ C++
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m_alloc.destroy(scratchBuffer);
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m_alloc.destroy(stagingBuffer);
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}
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~~~~
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# BLAS Animation
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In the previous chapter, we updated the transformation matrices. In this one we will modify vertices in a compute shader.
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## Adding a Sphere
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In this chapter, we will animate a sphere. In `main.cpp`, set up the scene like this:
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~~~~ C++
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helloVk.loadModel(nvh::findFile("media/scenes/plane.obj", defaultSearchPaths),
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nvmath::scale_mat4(nvmath::vec3f(2.f, 1.f, 2.f)));
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helloVk.loadModel(nvh::findFile("media/scenes/wuson.obj", defaultSearchPaths));
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HelloVulkan::ObjInstance inst = helloVk.m_objInstance.back();
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for(int i = 0; i < 5; i++)
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helloVk.m_objInstance.push_back(inst);
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helloVk.loadModel(nvh::findFile("media/scenes/sphere.obj", defaultSearchPaths));
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~~~~
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Because we now have a new instance, we have to adjust the calculation of the number of Wuson models in `HelloVulkan::animationInstances()`.
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~~~~ C++
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const int32_t nbWuson = static_cast<int32_t>(m_objInstance.size() - 2);
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~~~~
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## Compute Shader
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The compute shader will update the vertices in-place.
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Add all of the following members to the `HelloVulkan` class:
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~~~~ C++
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void createCompDescriptors();
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void updateCompDescriptors(nvvkBuffer& vertex);
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void createCompPipelines();
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nvvk::DescriptorSetBindings m_compDescSetLayoutBind;
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vk::DescriptorPool m_compDescPool;
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vk::DescriptorSetLayout m_compDescSetLayout;
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vk::DescriptorSet m_compDescSet;
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vk::Pipeline m_compPipeline;
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vk::PipelineLayout m_compPipelineLayout;
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~~~~
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The compute shader will work on a single `VertexObj` buffer.
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~~~~ C++
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void HelloVulkan::createCompDescriptors()
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{
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m_compDescSetLayoutBind.addBinding(vk::DescriptorSetLayoutBinding(
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0, vk::DescriptorType::eStorageBuffer, 1, vk::ShaderStageFlagBits::eCompute));
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m_compDescSetLayout = m_compDescSetLayoutBind.createLayout(m_device);
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m_compDescPool = m_compDescSetLayoutBind.createPool(m_device, 1);
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m_compDescSet = nvvk::allocateDescriptorSet(m_device, m_compDescPool, m_compDescSetLayout);
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}
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~~~~
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`updateCompDescriptors` will set the set the descriptor to the buffer of `VertexObj` objects to which the animation will be applied.
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~~~~ C++
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void HelloVulkan::updateCompDescriptors(nvvkBuffer& vertex)
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{
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std::vector<vk::WriteDescriptorSet> writes;
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vk::DescriptorBufferInfo dbiUnif{vertex.buffer, 0, VK_WHOLE_SIZE};
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writes.emplace_back(m_compDescSetLayoutBind.makeWrite(m_compDescSet, 0, dbiUnif));
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m_device.updateDescriptorSets(static_cast<uint32_t>(writes.size()), writes.data(), 0, nullptr);
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}
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~~~~
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The compute pipeline will consist of a simple shader and a push constant, which will be used
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to set the animation time.
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~~~~ C++
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void HelloVulkan::createCompPipelines()
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{
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// pushing time
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vk::PushConstantRange push_constants = {vk::ShaderStageFlagBits::eCompute, 0, sizeof(float)};
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vk::PipelineLayoutCreateInfo layout_info{{}, 1, &m_compDescSetLayout, 1, &push_constants};
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m_compPipelineLayout = m_device.createPipelineLayout(layout_info);
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vk::ComputePipelineCreateInfo computePipelineCreateInfo{{}, {}, m_compPipelineLayout};
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computePipelineCreateInfo.stage =
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nvvk::createShaderStageInfo(m_device,
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nvh::loadFile("shaders/anim.comp.spv", true, defaultSearchPaths),
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VK_SHADER_STAGE_COMPUTE_BIT);
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m_compPipeline = m_device.createComputePipeline({}, computePipelineCreateInfo, nullptr);
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m_device.destroy(computePipelineCreateInfo.stage.module);
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}
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~~~~
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Finally, destroy the resources in `HelloVulkan::destroyResources()`:
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~~~~ C++
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m_device.destroy(m_compDescPool);
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m_device.destroy(m_compDescSetLayout);
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m_device.destroy(m_compPipeline);
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m_device.destroy(m_compPipelineLayout);
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~~~~
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## `anim.comp`
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The compute shader will be simple. We need to add a new shader file, `anim.comp`, to the `shaders` filter in the solution.
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This will move each vertex up and down over time.
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~~~~ C++
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#version 460
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#extension GL_ARB_separate_shader_objects : enable
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#extension GL_EXT_scalar_block_layout : enable
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#extension GL_GOOGLE_include_directive : enable
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#include "wavefront.glsl"
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layout(binding = 0, scalar) buffer Vertices
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{
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Vertex v[];
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}
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vertices;
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layout(push_constant) uniform shaderInformation
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{
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float iTime;
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}
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pushc;
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void main()
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{
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Vertex v0 = vertices.v[gl_GlobalInvocationID.x];
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// Compute vertex position
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const float PI = 3.14159265;
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const float signY = (v0.pos.y >= 0 ? 1 : -1);
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const float radius = length(v0.pos.xz);
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const float argument = pushc.iTime * 4 + radius * PI;
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const float s = sin(argument);
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v0.pos.y = signY * abs(s) * 0.5;
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// Compute normal
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if(radius == 0.0f)
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{
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v0.nrm = vec3(0.0f, signY, 0.0f);
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}
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else
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{
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const float c = cos(argument);
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const float xzFactor = -PI * s * c;
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const float yFactor = 2.0f * signY * radius * abs(s);
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v0.nrm = normalize(vec3(v0.pos.x * xzFactor, yFactor, v0.pos.z * xzFactor));
|
|
}
|
|
|
|
vertices.v[gl_GlobalInvocationID.x] = v0;
|
|
}
|
|
~~~~
|
|
|
|
## Animating the Object
|
|
|
|
First add the declaration of the animation function in `HelloVulkan`:
|
|
|
|
~~~~ C++
|
|
void animationObject(float time);
|
|
~~~~
|
|
|
|
The implementation only pushes the current time and calls the compute shader (`dispatch`).
|
|
|
|
~~~~ C++
|
|
void HelloVulkan::animationObject(float time)
|
|
{
|
|
ObjModel& model = m_objModel[2];
|
|
|
|
updateCompDescriptors(model.vertexBuffer);
|
|
|
|
nvvk::CommandPool genCmdBuf(m_device, m_graphicsQueueIndex);
|
|
vk::CommandBuffer cmdBuf = genCmdBuf.createCommandBuffer();
|
|
|
|
cmdBuf.bindPipeline(vk::PipelineBindPoint::eCompute, m_compPipeline);
|
|
cmdBuf.bindDescriptorSets(vk::PipelineBindPoint::eCompute, m_compPipelineLayout, 0,
|
|
{m_compDescSet}, {});
|
|
cmdBuf.pushConstants(m_compPipelineLayout, vk::ShaderStageFlagBits::eCompute, 0, sizeof(float),
|
|
&time);
|
|
cmdBuf.dispatch(model.nbVertices, 1, 1);
|
|
genCmdBuf.submitAndWait(cmdBuf);
|
|
}
|
|
~~~~
|
|
|
|
## Invoking Animation
|
|
|
|
In `main.cpp`, after the other resource creation functions, add the creation functions for the compute shader.
|
|
|
|
~~~~ C++
|
|
helloVk.createCompDescriptors();
|
|
helloVk.createCompPipelines();
|
|
~~~~
|
|
|
|
In the rendering loop, after the call to `animationInstances`, call the object animation function.
|
|
|
|
~~~~ C++
|
|
helloVk.animationObject(diff.count());
|
|
~~~~
|
|
|
|
!!! Note
|
|
At this point, the object should be animated when using the rasterizer, but should still be immobile when using the ray tracer.
|
|
|
|
## Update BLAS
|
|
|
|
In `nvvk::RaytracingBuilder` in `raytrace_vkpp.hpp`, we can add a function to update a BLAS whose vertex buffer was previously updated. This function is very similar to the one used for instances, but in this case, there is no buffer transfer to do.
|
|
|
|
~~~~ C++
|
|
//--------------------------------------------------------------------------------------------------
|
|
// Refit the BLAS from updated buffers
|
|
//
|
|
void updateBlas(uint32_t blasIdx)
|
|
{
|
|
Blas& blas = m_blas[blasIdx];
|
|
|
|
// Compute the amount of scratch memory required by the AS builder to update the BLAS
|
|
VkAccelerationStructureMemoryRequirementsInfoKHR memoryRequirementsInfo{
|
|
VK_STRUCTURE_TYPE_ACCELERATION_STRUCTURE_MEMORY_REQUIREMENTS_INFO_KHR};
|
|
memoryRequirementsInfo.type = VK_ACCELERATION_STRUCTURE_MEMORY_REQUIREMENTS_TYPE_UPDATE_SCRATCH_KHR;
|
|
memoryRequirementsInfo.accelerationStructure = blas.as.accel;
|
|
memoryRequirementsInfo.buildType = VK_ACCELERATION_STRUCTURE_BUILD_TYPE_DEVICE_KHR;
|
|
|
|
VkMemoryRequirements2 reqMem{VK_STRUCTURE_TYPE_MEMORY_REQUIREMENTS_2};
|
|
vkGetAccelerationStructureMemoryRequirementsKHR(m_device, &memoryRequirementsInfo, &reqMem);
|
|
VkDeviceSize scratchSize = reqMem.memoryRequirements.size;
|
|
|
|
// Allocate the scratch buffer
|
|
nvvkBuffer scratchBuffer =
|
|
m_alloc.createBuffer(scratchSize, VK_BUFFER_USAGE_RAY_TRACING_BIT_KHR | VK_BUFFER_USAGE_SHADER_DEVICE_ADDRESS_BIT);
|
|
VkBufferDeviceAddressInfo bufferInfo{VK_STRUCTURE_TYPE_BUFFER_DEVICE_ADDRESS_INFO};
|
|
bufferInfo.buffer = scratchBuffer.buffer;
|
|
VkDeviceAddress scratchAddress = vkGetBufferDeviceAddress(m_device, &bufferInfo);
|
|
|
|
|
|
const VkAccelerationStructureGeometryKHR* pGeometry = blas.asGeometry.data();
|
|
VkAccelerationStructureBuildGeometryInfoKHR asInfo{VK_STRUCTURE_TYPE_ACCELERATION_STRUCTURE_BUILD_GEOMETRY_INFO_KHR};
|
|
asInfo.type = VK_ACCELERATION_STRUCTURE_TYPE_BOTTOM_LEVEL_KHR;
|
|
asInfo.flags = blas.flags;
|
|
asInfo.update = VK_TRUE;
|
|
asInfo.srcAccelerationStructure = blas.as.accel;
|
|
asInfo.dstAccelerationStructure = blas.as.accel;
|
|
asInfo.geometryArrayOfPointers = VK_FALSE;
|
|
asInfo.geometryCount = (uint32_t)blas.asGeometry.size();
|
|
asInfo.ppGeometries = &pGeometry;
|
|
asInfo.scratchData.deviceAddress = scratchAddress;
|
|
|
|
std::vector<const VkAccelerationStructureBuildOffsetInfoKHR*> pBuildOffset(blas.asBuildOffsetInfo.size());
|
|
for(size_t i = 0; i < blas.asBuildOffsetInfo.size(); i++)
|
|
pBuildOffset[i] = &blas.asBuildOffsetInfo[i];
|
|
|
|
// Update the instance buffer on the device side and build the TLAS
|
|
nvvk::CommandPool genCmdBuf(m_device, m_queueIndex);
|
|
VkCommandBuffer cmdBuf = genCmdBuf.createCommandBuffer();
|
|
|
|
|
|
// Update the acceleration structure. Note the VK_TRUE parameter to trigger the update,
|
|
// and the existing BLAS being passed and updated in place
|
|
vkCmdBuildAccelerationStructureKHR(cmdBuf, 1, &asInfo, pBuildOffset.data());
|
|
|
|
genCmdBuf.submitAndWait(cmdBuf);
|
|
m_alloc.destroy(scratchBuffer);
|
|
}
|
|
~~~~
|
|
|
|
The previous function (`updateBlas`) uses geometry information stored in `m_blas`.
|
|
To be able to re-use this information, we need to keep the structure of `nvvk::RaytracingBuilderKHR::Blas` objects
|
|
used for its creation.
|
|
|
|
Move the `nvvk::RaytracingBuilderKHR::Blas` vector from `HelloVulkan::createBottomLevelAS()` to the `HelloVulkan` class, renaming it to `m_blas`.
|
|
|
|
~~~~ C++
|
|
std::vector<nvvk::RaytracingBuilderKHR::Blas> m_blas;
|
|
~~~~
|
|
|
|
As with the TLAS, the BLAS needs to allow updates. We will also enable the
|
|
`VK_BUILD_ACCELERATION_STRUCTURE_PREFER_FAST_BUILD_BIT_KHR` flag, which indicates that the given
|
|
acceleration structure build should prioritize build time over trace performance.
|
|
|
|
~~~~ C++
|
|
void HelloVulkan::createBottomLevelAS()
|
|
{
|
|
// BLAS - Storing each primitive in a geometry
|
|
m_blas.reserve(m_objModel.size());
|
|
for(const auto & obj : m_objModel)
|
|
{
|
|
auto blas = objectToVkGeometryKHR(obj);
|
|
|
|
// We could add more geometry in each BLAS, but we add only one for now
|
|
m_blas.push_back(blas);
|
|
}
|
|
m_rtBuilder.buildBlas(m_blas, vk::BuildAccelerationStructureFlagBitsKHR::eAllowUpdate
|
|
| vk::BuildAccelerationStructureFlagBitsKHR::ePreferFastBuild);
|
|
}
|
|
~~~~
|
|
|
|
Finally, we can add a line at the end of `HelloVulkan::animationObject()` to update the BLAS.
|
|
|
|
~~~~ C++
|
|
m_rtBuilder.updateBlas(2);
|
|
~~~~
|
|
|
|
|
|
|
|
</script>
|
|
|
|
# Final Code
|
|
|
|
You can find the final code in the folder [ray_tracing_animation](https://github.com/nvpro-samples/vk_raytracing_tutorial_KHR/tree/master/ray_tracing_animation)
|
|
|
|
|
|
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