I'm in the process of porting some rendering code to Vulkan. I've been using the SPIR-V cross-compiler to avoid the requirement of re-writing all my shaders, which has been working well in most cases, but now I've hit an issue I just can't get past.
I have a vertex shader being compiled to SPIR-V that uses SV_RenderTargetArrayIndex. This maps to ShaderViewportIndexLayerEXT in SPIRV. The device I'm running on (an NVidia 3090 with latest drivers) supports the VK_EXT_shader_viewport_index_layer extension (which is core in 1.2), and I'm explicitly enabling both shaderOutputViewportIndex and shaderOutputLayer in the VkPhysicalDeviceVulkan12Features struct (chained off the vkPhysicalDeviceFeatures2 which is in turn chained on pNext for the vkDeviceCreateInfo struct.
I've also added the line:
[[vk::ext_extension("SPV_EXT_shader_viewport_index_layer")]]
To the .hlsl source file, and verified the SPIRV being output contains the extension reference.
The validation layer is whining, with:
Validation Error: [ VUID-VkShaderModuleCreateInfo-pCode-01091 ] Object 0: handle = 0x1e66c477eb0, type = VK_OBJECT_TYPE_DEVICE; | MessageID = 0xa7bb8db6 | vkCreateShaderModule(): The SPIR-V Capability (ShaderViewportIndexLayerEXT) was declared, but none of the requirements were met to use it. The Vulkan spec states: If pCode declares any of the capabilities listed in the SPIR-V Environment appendix, one of the corresponding requirements must be satisfied
Is there something else I need to do to enable this feature on the device? Any help/insight would be greatly appreciated.
(I can always drop the requirement to use this feature - realistically in my use case on DX12 it's not gaining me much if anything, but I'd rather figure this out!)