Autodesk: Lavapipe support on macOS

[erikaharrison-adsk]

Description of Change(s)

⚠ Note: This PR is for feature-hgi-vulkan branch.

The main goal is to enable Lavapipe (Vulkan driver) as a software rasterizer on all supported platforms, for testing purposes. This PR addresses macOS support by fixing some Vulkan instance and device creation issues/bugs.

Enabling MoltenVK support could be useful for testing, but it's not a priority, and there are issues with geometry shaders support preventing that, which this PR does not address. HgiVulkan currently assumes that geometry shaders are always supported, although it is actually an optional feature. If a feature check is added, then this could be fixed.

Lavapipe doesn't support Metal surfaces (VK_EXT_metal_surface), but display still works thanks to the HgiInterop Vulkan path:

• After building the list of desired instance extensions, remove any that are not actually available. This mostly serves to remove the VK_EXT_metal_surface extension when using Lavapipe, since it doesn't support it.
• Make the VK_KHR_swapchain device extension optional. It is not available if Lavapipe is built without any selected platforms, as it won't support any surface output.

Update Vulkan support to the latest recommendations for macOS, based on this document from LunarG:

• Do no statically link with the MoltenVK libraries. The desired Vulkan driver should instead by loaded through the ICD loader. This is mandatory for loading the Lavapipe drivers.
• Replace the deprecated VK_MVK_macos_surface instance extension with VK_EXT_metal_surface.
• Add the VK_KHR_portability_enumeration instance extension on macOS. This is required for MoltenVK, but not for Lavapipe (it's a Vulkan 1.3 conformant implementation).
• VK_EXT_descriptor_indexing is available on Lavapipe and MoltenVK (partial support), remove the conditional compilation for macOS.

With these changes, using Lavapipe, USDView launches and can display some test scenes, although more testing is required to identify remaining issues. Unit tests also all pass, although many graphics tests are skipped on macOS.

Fixes Issue(s)

• N/A

• I have verified that all unit tests pass with the proposed changes

• I have submitted a signed Contributor License Agreement

[jesschimein]

Filed as internal issue #USD-9759

[jesschimein]

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