Reply To: About Portal Area Light

Hi Keswick,

Awesome you took the time to dive into this!

From what I’ve experienced there’s about a 100 settings you can optimize for faster renders, if not more. Each has it’s own benefit and drawback and usually combining multiple of them works best, as well as making changes that fit your scene e.g. path optimization for a scene with caustics. 

Anyways here’s the funny part though; on better hardware setups the difference, especially when doing only 1 or 2 optimizations, can actually be 0 or even a net negative (longer renders). I don’t know why, or how, that happens and I expect this is something that would require both some of the big brains at Blender AS WELL AS people over at the GPU manufacturer. 

I’ve done multiple videos on render performance and re-rendering the same scene 100’s of times, with the exact same settings, still has resulted in HUGELY varied results. A 1 min 30 sec render could range anywhere from 1 min 25 sec to 1 min 35 sec, with 0 changes to the settings. My idea is that Blender and your GPU play in synchrony and that this balance of communication between the software and the hardware is what drives the final speed of the render. This communication varies depending on other stuff your PC is doing, even when personally not doing anything. Background tasks, CPU usage, GPU usage for things etc or even the time between renders (waiting longer seemed to give my GPU some breathing room and made the renders faster?!). Again 100’s of factors.

I believe that adding these small optimizations in the long run is a positive, as understanding they exist and applying them is useful for when you really need it. In all other scenario’s it might add a few seconds of rendering, but that ‘is what it is’.

Cheers and happy rendering!