examples of rendertime differences

[Kevin F]

Hi Kevin,

I suspect this may be an efficiency problem with global illumination, as I've observed a similar problem. Can you repeat the test with the Enviro Light disabled? (Don't worry about other GI settings.)

Matt

Hi Matt,

Just repeated the test on a slightly adjusted scene (pov changed a little) with the Enviro Light disabled - same problem i'm afraid. 320x240 = 14min 38 sec, 640x480 = 3hr 51min 48sec.

edit:
just done a basic "default" render - default plus power fractal terrain with camera close to ground. With Enviro Light on a 320 render took 1min 40sec, and a 640 took 7min 27sec.  a little over 4 times as long. But with the Enviro Light disabled the 320 took 1min 5 sec and the 640 took 4 min 17 sec = i.e. 4 times as long! So there is an issue here.
The big differences in my original renders are obviously made worse by the complexity of the scene - especially extensive use of the water shader and 3 lots of fake stones which were all image mapped.
Hope this is of use.
Regards
Kevin.


Regards
Kevin.

[Matt]

Hi Kevin,

I think you're right about the complexity of the scene. I think the water is probably the main reason for the non-linear increase in render time. GI also has this problem according to my tests, but reflections in rough surfaces seem to be much worse. It's probably due to the high number of micropolygons that need to be generated for reflections, and at higher resolutions it becomes more difficult for TG2 to cache enough micropolygons to keep it fast. With smooth water you might get better results because the coherence of the reflection rays makes it easier to cache the reflected micropolygons.

Matt