Regarding Time Complexity of Scene and Path Computation in Sionna

[WeirdoooK]

I am currently working on optimizing a scene in Sionna, and I would like to understand the time complexity with respect to the following parameters:

Number of Objects in the Scene: As the number of materials (reflective surfaces, objects) increases in the scene, how does this affect the computational complexity? Specifically, does the complexity grow linearly or quadratically with the number of objects?

Number of Scattered Paths: When the number of scattered paths increases (due to path tracing or more detailed ray modeling), how does the time complexity change? Is it a linear or higher-order growth?

Number of Parameters per Material to Infer: How does the time complexity change when more parameters need to be inferred per material (e.g., conductivity, relative permittivity)?

A more theoretical explanation of how these factors contribute to the overall time complexity in big-O notation would be greatly appreciated. Additionally, if there are any related documents or reference materials available, could you kindly share them for further reading?

[merlinND]

Hello @WeirodoK,

Here are some high-level answers to give an intuition. I would refer to the Sionna RT Technical report for more details.

Number of Objects in the Scene

Generally, ray tracing cost increases with the number of primitives (triangles, i.e. geometric complexity) in the scene.
For Sionna RT however, a more important factor is the number of unique radio materials present in the scene. The merge_shape options of load_scene() can greatly improve performance, as long as the number of unique materials in the scene is not too large.

Number of Scattered Paths

The computation cost grows linearly with the number of paths. But that's also the dimension that is massively parallelized on the GPU, so you should find that many, many paths can be handled in parallel without a great increase in runtime, until the GPU is saturated.

Number of Parameters per Material to Infer

I don't think this would influence the run time much.

[SebastianCa]

This is not an issue with the Sionna code