Vulkan for XR tutorial using Simple Engine

[gpx1000]

Add engine integration sections for spatial computing chapters 10-20
Add "Incorporating into the Engine" sections demonstrating practical implementation of Variable Rate Shading, Canted Displays, CAVE Architecture, Warp and Blend, LightField Theory, Plenoptic Synthesis, Scene Understanding, ML Inference, Semantic Occlusion, Platform Divergence, and Spatial Diagnostics CI/CD. Include C++ code examples for renderer_core.cpp, renderer_rendering.cpp, and engine.cpp showing feature enablement, pipeline setup, and compute passes using Vulkan 1.4 and Slang shaders.

This is a WIP currently, doing this to help test the CI scripts.

[SaschaWillems]

That's a pretty comprehensive PR 👍🏻

Will prob. take some time to review this, but at first glance: Can we lower the baseline from Vulkan 1.4 to 1.3? 1.4 didn't add that much, but it has very limited support on mobile.

[SaschaWillems]

Did a first quick review. I don't have much experience with OpenXR, but this looks good to me and was easy to follow.

Aside from the comments, I'd like to see links to existing documentation like the tutorial, the spec and/or the guide, making it easier for people to discover relevant adjacent information.

[SaschaWillems]

CMake setup for the source fails for me, but maybe I'm doing something wrong (I didn't find build instructions for the OpenXR engine variation). When running CMake from the attachments/openxr_engine folder, I get the following errors:

CMake Error at V:/Vulkan-Docs-Site/Vulkan-Tutorial-review/attachments/simple_engine/CMake/Findtinygltf.cmake:80 (file):
  file failed to create symbolic link
  'V:/Vulkan-Docs-Site/Vulkan-Tutorial-review/attachments/openxr_engine/build/_deps/tinygltf-src/nlohmann/json.hpp':
  Dem Client fehlt ein erforderliches Recht.

Call Stack (most recent call first):
  CMakeLists.txt:22 (find_package)


CMake Error at C:/Program Files/CMake/share/cmake-4.1/Modules/FindPackageHandleStandardArgs.cmake:227 (message):
  Could NOT find KTX (missing: KTX_INCLUDE_DIR KTX_LIBRARY)
Call Stack (most recent call first):
  C:/Program Files/CMake/share/cmake-4.1/Modules/FindPackageHandleStandardArgs.cmake:591 (_FPHSA_FAILURE_MESSAGE)
  V:/Vulkan-Docs-Site/Vulkan-Tutorial-review/attachments/simple_engine/CMake/FindKTX.cmake:55 (find_package_handle_standard_args)
  CMakeLists.txt:23 (find_package)

[SaschaWillems]

Documentation looks good and the code builds, but it crashes for me inside QueueFamilyIndices Renderer::findQueueFamilies at device.getSurfaceSupportKHR (Line 150).

I get the following validation layer error before the crash:

Validation layer: vkGetPhysicalDeviceSurfaceSupportKHR(): surface Invalid VkSurfaceKHR Object 0x1fff5c6dc10.
The Vulkan spec states: surface must be a valid VkSurfaceKHR handle (https://docs.vulkan.org/spec/latest/chapters/VK_KHR_surface/wsi.html#VUID-vkGetPhysicalDeviceSurfaceSupportKHR-surface-parameter)
Validation layer: vkGetPhysicalDeviceSurfaceSupportKHR(): Couldn't find VkSurfaceKHR Object 0x1fff5c6dc10. This should not happen and may indicate a bug in the application.

This is on Windows with an RTX 4070 using Meta's OpenXR simulator.

[gpx1000]

Give that another try. I haven't tried it in Meta's OpenXR simulator,. But it does seem to work in monada runtime and our runtime. I did test it in Windows so hopefully Meta's runtime will be good to go.

[SaschaWillems]

Thanks. It's now starting up. But I do get some validation errors:

 vkCreateDevice(): If the pNext chain includes a VkPhysicalDeviceVulkan11Features structure, then it must not include a VkPhysicalDeviceMultiviewFeatures structure. The features in VkPhysicalDeviceMultiviewFeatures were promoted in Vulkan 1.1 and is also found in VkPhysicalDeviceVulkan11Features. To prevent one feature setting something to VK_TRUE and the other to VK_FALSE, only one struct containing the feature is allowed.
pNext chain: VkDeviceCreateInfo::pNext -> [VK_STRUCTURE_TYPE_LOADER_DEVICE_CREATE_INFO] -> [VK_STRUCTURE_TYPE_LOADER_DEVICE_CREATE_INFO] -> [VkPhysicalDeviceFeatures2] -> [VkPhysicalDeviceMultiviewFeatures] -> [VkPhysicalDeviceTimelineSemaphoreFeatures] -> [VkPhysicalDeviceVulkanMemoryModelFeatures] -> [VkPhysicalDeviceBufferDeviceAddressFeatures] -> [VkPhysicalDevice8BitStorageFeatures] -> [VkPhysicalDeviceVulkan11Features] -> [VkPhysicalDeviceVulkan13Features] -> [VkPhysicalDeviceDescriptorIndexingFeatures] -> [VkPhysicalDeviceRobustness2FeaturesKHR] -> [VkPhysicalDeviceDynamicRenderingLocalReadFeatures] -> [VkPhysicalDeviceAccelerationStructureFeaturesKHR] -> [VkPhysicalDeviceRayQueryFeaturesKHR].
The Vulkan spec states: If the pNext chain includes a VkPhysicalDeviceVulkan11Features structure, then it must not include a VkPhysicalDevice16BitStorageFeatures, VkPhysicalDeviceMultiviewFeatures, VkPhysicalDeviceVariablePointersFeatures, VkPhysicalDeviceProtectedMemoryFeatures, VkPhysicalDeviceSamplerYcbcrConversionFeatures, or VkPhysicalDeviceShaderDrawParametersFeatures structure (https://docs.vulkan.org/spec/latest/chapters/devsandqueues.html#VUID-VkDeviceCreateInfo-pNext-02829)

and

Validation layer: vkCreatePipelineCache(): pCreateInfo->flags includes VK_PIPELINE_CACHE_CREATE_EXTERNALLY_SYNCHRONIZED_BIT, but pipelineCreationCacheControl feature was not enabled.
The Vulkan spec states: If the pipelineCreationCacheControl feature is not enabled, flags must not include VK_PIPELINE_CACHE_CREATE_EXTERNALLY_SYNCHRONIZED_BIT (https://docs.vulkan.org/spec/latest/chapters/pipelines.html#VUID-VkPipelineCacheCreateInfo-pipelineCreationCacheControl-02892)

And afterwards I do see the Meta XR simulator spinning up, but all I get is a white screen.

Last line in std::out is:

Requesting acceleration structure build for loaded scene...

Then pressing any key results in an assertion;

Assertion failed: ImGui::IsNamedKeyOrMod(key), file V:\Vulkan-Docs-Site\Vulkan-Tutorial-review\attachments\simple_engine\imgui\imgui.cpp, line 1850

Not sure if any of this is related to the Meta XR Simulator.