Leveraging RTX hardware capabilities with OptiX 7.0

[droettger]

To my understanding of both the docs and some discussions on this board, all I have to do is to stick to the OptiX built-in triangles (i.e. do not use geometry types other than “OPTIX_BUILD_INPUT_TYPE_TRIANGLES”). OptiX then “transparently” makes use of RTX capabilities where possible

That is correct.
The RT cores inside the RTX Turing boards accelerate two parts of ray tracing, the BVH traversal and the triangle intersection.

Both will run fully on the RT cores (in contrast to running on the Streaming Multiprocessors (SM)) when the BVH hierachy has two levels. Means a maximum of two acceleration structures (AS) from root node to leaf triangle geometry, which means for the scene structure an Instance AS (IAS) and Geometry AS (GAS) with triangles. The transform in the instances is hardware accelerated.

Are there any explicit steps to be taken to ensure my code makes use of RTX hardware capabilities during evaluation?

That’s basically all, but OptiX also supports only one GAS and also multiple IAS levels. The latter will run the BVH traversal only partially on the RT cores. (The overall maximum traversal depth can be queried via OPTIX_DEVICE_PROPERTY_LIMIT_MAX_TRAVERSABLE_GRAPH_DEPTH.)
Also whenever there is motion-blur inside the scene in the instances or geometry, the BVH traversal will become more expensive.
For custom geometric primitives, only the BVH traversal will be hardware accelerated but then calls back into your intersection shaders running on the SMs.
There are other things which call back into the SMs like anyhit programs.
Have a closer look at the available optixTrace() flags which can control some of the program domain invocations.

I’d recommend to watch the “OptiX Performance Tools and Tricks” presentation for more information:
https://devtalk.nvidia.com/default/topic/1062216/optix/optix-talks-from-siggraph-2019/

Also, is there a way to verify the use of the RTX hardware acceleration during runtime? I am aware of querying “OPTIX_DEVICE_PROPERTY_RTCORE_VERSION” using “optixDeviceContextGetProperty()”. But this only yields the device’s capabilities - not the capabilities’ use.

Not really. It’s happening automatically if you’re building the scene according to the above structure.

Due to limited access to RTX capable hardware, I’m developing on a “non-RTX” graphics card (GeForce GTX 960, driver version 436.30, CUDA 10.1, OptiX 7.0). Evaluation will later take place on a RTX capable device (the exact card is still to be determined).

Mind that a GTX 960 is an entry-level board of a three GPU generations older architecture. It will be far from representative of the possible performance of even the smallest RTX board in everything you throw at it.