bagginsbill: > Quote - For simpler scenes 1 thread per core is fastest because there's no overhead of context switching between threads. This is not news. If, however, you have a rendering thread waiting for disk I/O, in a scene with lots of large textures, then doubling the threads can help.

When I say lots of textures, I mean at least 30 texture files at 4K by 4K each. A simple room or a couple of figures isn't going to meet that requirement.

Basically, watch your task manager, if you're not at 100% CPU across all cores, use more threads. If you are at 100% with 1 thread per core, then you have the entire scene in memory, by definition in this context a "simple" scene, and adding more threads will slow it down slightly.

I had a Vista gadget open showing % load for RAM and each core, and my tests confirm this. 

Note, I was using complex materials in the test scene.  

Running four threads on a Core i7 quad processor, each core would periodically cycle between 100% and idle. 

Running eight threads, each core stayed at/near 100% with only occasional momentary dips to about 75%.

Running sixteen threads also kept the cores busy, but it didn't result in a faster render time.   I tried an even more complex scene, but P8 ran out of memory trying to render it at 2560x1600 pixels at final quality settings with ray-traced shadows and IDL.  P7 also failed at that size frequently.  In such cases, I use Poser Pro.

Poser 12, in feet.  

OSes:  Win7Prox64, Win7Ultx64

Silo Pro 2.5.6 64bit, Vue Infinite 2014.7, Genetica 4.0 Studio, UV Mapper Pro, UV Layout Pro, PhotoImpact X3, GIF Animator 5