GI and CPU usage

[David Sander]

I've got a simple scene involving a dozen basic geometric shapes, and I'm lighting the scene wholly using Global Illumination.

On rendering a full res snapshot, the Calculating GI Buffer phase in Camera suddenly goes extremely slowly, and in my Mac's Activity Monitor utility, I'm seeing CPU usage maxed out. A basic scene with 604,000 polys, no lights and small textures isn't something I'm expecting to take five minutes per HD frame to render on a machine with 32Gb RAM and 2 x 2.93GHz Quad-core Intel Xeon processors - not when I was able to render a scene earlier today with frames taking less than 30 seconds to crank out. This is the first time I've encountered something like this.

In the GI controls I have set secondary rays to zero and slightly decreased the ray count to 180 in the hope this would help, but so far nothing has changed. I'm using Sky Color instead of a skymap. Not sure what else to tweak in order to bring this monster render time down to a dull roar.

Any suggestions welcome.

David

[S. Houtzager]

Hey David,

 

Would have to know what version of EI you are using and what your render times are looking like at what size of resolution.  GI is just going to be slower no matter what.  I have gotten good renderings with the ray count at 100. You could tweek the Sampling options down slightly to speed up the process. 

 

What are your light shadows set to? If you turn on the box for use GI sampling Engine it will speed it up. There is the Photons option. but using Photons means no specular hilights so you would need additional lights just for that.

[Tomas Egger]

Ola David,

 

Try to render the same scene using 32 bits and 64 bits architecture (Camera settings), tell me the render times.

 

Thanks

 

Tom

[Brian]

I've noticed that when it's calculating secondary rays or the GI buffer it's only using about 1 core (I don't know why this is) but then when it gets to shading surfaces all the cores kick in!

 

The other thing is.....if you're ram is maxed (10.8 sucks at dumping the ram) you're toast until you flush your ram out. There's a command in terminal (instead of having to restart your computer). I think it's  "purge".