Q: Raytracing support?

[ib00]

Cool API! Finally something reasonable.

Any plans on supporting raytracing? If so, what would the direction of the API be? Something similar to a texture heap,
but for acceleration structure?

[sebbbi]

I am considering ray-tracing. It wasn't included in my blog post or SIGGRAPH talk, because ray-tracing APIs are too complicated currently. Fights against the simplicity principle. But inline ray-tracing (intrinsics) would work. Need to investigate how big is the API complexity cost.

[tarmo888]

Is the inline one VK_KHR_ray_query?

EXTS=(
    "VK_KHR_ray_tracing_pipeline"
    "VK_KHR_acceleration_structure"
    "VK_KHR_ray_query"
    "VK_KHR_deferred_host_operations"
    "VK_KHR_pipeline_library"
    "VK_NV_ray_tracing"
)
INFO=$(vulkaninfo)
echo -e "\n--- Ray Tracing Extension Check ---"
for ext in "${EXTS[@]}"; do
    if grep -Fq "$ext" <<< "$INFO"; then
        echo -e "\e[32m[✓] Supported: $ext\e[0m"
    else
        echo -e "\e[31m[X] Missing:   $ext\e[0m"
    fi
done
echo -e "---------------------------------"

I ran this on GTX 1660 Super and got this result:

--- Ray Tracing Extension Check ---
[✓] Supported: VK_KHR_ray_tracing_pipeline
[✓] Supported: VK_KHR_acceleration_structure
[X] Missing:   VK_KHR_ray_query
[✓] Supported: VK_KHR_deferred_host_operations
[✓] Supported: VK_KHR_pipeline_library
[✓] Supported: VK_NV_ray_tracing
---------------------------------

[ib00]

Yeah, the raytracing API is a a mess and extension nightmare.

I think it should be doable along the similar direction as texture heap and do accel heap.
And add a few more commands like build_blas, build_tlas, refit, compact.

But, yeah, you are immediately adding lots of complexity.

[sebbbi]

@tarmo888 yes, the VK_KHR_ray_query is similar to DXR 1.1 ray-query. IIRC even the first-gen RT hardware (Turing) got driver update to support it. If we expose ray-tracing, this seems the way to go.

[tarmo888]

@sebbbi as i understand, DXR ray-query was backported to GTX 16 series, but Vulkan VK_KHR_ray_query was not.

[sebbbi]

GTX 16 has no hardware ray-test units. It’s running on software emulation in DX12.

[tarmo888]

Tested on WSL2 using Mesa's Dozen (dzn) Vulkan driver, which translates
Vulkan to Direct3D 12. The driver reports the following ray-tracing extensions:

WARNING: dzn is not a conformant Vulkan implementation, testing use only.

--- Ray Tracing Extension Check ---
[✓] Supported: VK_KHR_ray_tracing_pipeline
[✓] Supported: VK_KHR_acceleration_structure
[✓] Supported: VK_KHR_ray_query
[✓] Supported: VK_KHR_deferred_host_operations
[✓] Supported: VK_KHR_pipeline_library
[X] Missing:   VK_NV_ray_tracing
---------------------------------