What short-cuts are needed for real-time path tracing?

The movie industry uses render farms for this level of realism, so you must cut corners to make real-time path tracing a thing, right?

Well you might consider denoising to be a short-cut - but it’s not really. It allows you to extract a much better result from a poor signal. Users of offline path tracing, like the film industry, will still use denoising, but typically to a lesser degree.

To extract the most performance, real time path tracing will typically use fewer bounces than offline path tracing too. As with denoising, other parts of the pipeline (like ReSTIR DI and ReSTIR GI from RTXDI) can also rely on temporal reuse of data generated in previous frames.
Likewise, we can use lower precision math, simplified materials and skip a lot of computation necessary for subtle detail that is less noticeable in real-time.

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