At the moment, offline rendering is still massively parallel, but you run into memory limitations when trying to render on the GPU. High end VFX scenes using Re

At the moment, offline rendering is still massively parallel, but you run into memory limitations when trying to render on the GPU. High end VFX scenes using Renderman or Arnold can push up to 100 GB+ of memory and run for multiple hours on standard 12-24 core machines. I believe some GPU renderers can do "out-of-core" rendering, but not all of them support that yet. The high end renderers usually split up a large image into "buckets" and then perform path tracing on those regions of an image, and combine the results together. If you have more cores, you can increase the number of simultaneous buckets to evaluate. To put this in perspective, a lot of the recent news around real-time raytracing is when a game engine does 1-4 samples per pixel and then aggressively denoises (in 2D) the result. That's why you often see splotches or errors. On the other hand, high end VFX renders will end up doing hundreds or even thousands of samples per pixel to get a clean, high quality, physically plausible result.