Question about Iray That Could Be Solved By Experimentation (but i'm too lazy to do that)

404nicg

Hello all. My question is this: Do items that are not in the viewport and not being rendered affect render times by way of geometry calculations?Obviously if they are directly out of sight they could have an effect on shadows so that could affect the render with the whole occlusion thing. But say you're shooting a shot in a furnished house. Would things in a completely different room of the house from the shot you are rendering have any effect on the speed of the render? Thanks

Daywalker Designs

As far as I know, the won't have an impact on render speed, but they will impact whether or not you can fit the scene in VRAM.

kyoto kid

...in that way, yes they do affect speed for it will cause the process to dump to slower CPU mode and you trade all those CUDA cores for however many processor threads you have on your CPU which is significantly less.

Now here's where it can get even worse, If you also don't have a lot of system memory, like only 12 GB (out of which about 1.5 is permanently taken up by the OS and system utilities like drivers & such), and your scene with the Daz Programme open takes up say 7.1 GB total, both are taking that much up of your physical memory (as the they need to remain open during rendering).  This leaves you only 3.4 GB physical memory for rendering before it dumps to the virtual memory partition on your HDD which is yet even (almost glacially) slower.  I run into this latter situation quite often in Iray as I have only 12 GB and  tend to create fairly "big" scenes and, like you mention with regard to your outdoor ones, often have elements off camera for the purpose of casting shadows and reflections.

Keep in mind that in interior scenes in Iray for some reason tend to render more slowly than outdoor ones and the number of emissive lights you have will also impact render performance (not sure though if they necessarily increase the file size).  Other factors that also slow render time but don't necessarily bloat the file size much include fog, volumetric effects for dust, and light coming through windows/open doors.