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NanoGator
12-07-2003, 07:24 AM
Hmm... you know, LW's had the 'extra raytrace optimization' feature for a while now, but I've yet to find a situation where it actually may render times faster instead of slower. Anybody got some idea of what it optimizes for? Radiosity? Anti-aliasing? High poly? Low poly?

Para
12-07-2003, 08:51 AM
Well, it makes wonders when you use raytraced reflections and radiosity. 2 day render goes down to 2 hour render easily with a bit tweaking :)

kevman3d
12-07-2003, 09:03 AM
It also works for large detailed raytraced scenes - For instance, it actually slightly improved rendering time for a scene I did containing several hundred thousand of detailed modelled grassblades, each casting shadows on each other.

Other then that, and obviously the radiosity thing, it usually tends to make rendering longer IMHO... :)

colkai
12-08-2003, 09:54 AM
It certainly seems very scene specific.
If there is raytracing, it doesn't follow that it improves time.
I tend to just do a couple of lo-res tests and play with the settings.

samartin
12-08-2003, 11:25 AM
I believe that if you are rendering a scene with lot's of reflections going on it is faster with a lower number. I think it's due to the lower number being the number of reflection bounces...

That's my understanding...

minus
12-08-2003, 09:01 PM
Aye... there is a scene I think in the benchmark directory that has a curved mirror reflecting lots of other mirrors on a plane in front of it. The camera is pointing at the curved mirror. --

The higher the number...the more mirrors you can see in the background... the lower the number the fewer.

It basically says how many times a ray can bounce between two surfaces. -- If you have something like a glass in your scene... one of the first things I do is drop down raytrace optimization to around 5 instead of the default 16. Speeds things up a lot.

Finkster
12-08-2003, 09:43 PM
Originally posted by minus

It basically says how many times a ray can bounce between two surfaces. -- If you have something like a glass in your scene... one of the first things I do is drop down raytrace optimization to around 5 instead of the default 16. Speeds things up a lot.

That's the ray recursion limit, which i believe is independent of ray trace optimisation. I think ray trace optimisation is of noticeable benefit when lots of pixels are involved in ray tracing (shadows, reflections etc.). So a very large image (more pixels) will show more of a relative speed gain, than the same image at low resolution.

kevman3d
12-09-2003, 09:28 AM
FYI,

Page 16.8 in the manual does a good explaination on why and how Raytrace Optimisation works (and doesn't work).

Kev.

colkai
12-09-2003, 10:10 AM
Cheers Kev,
Ya live and learn eh?
Especially interesting about the motion blur pass multiplying the calc.

E_Moelzer
12-09-2003, 01:54 PM
Extra Raytrace Optimization is pretty usefull. Only situation where it really sucks , is when there are Subpatchobjkects in the scene.
Then the rendertimes can get much higher than without.
CU
Elmar

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