Pre Calc secondary bounce set to none_SLOW!

[grasshopper]

Hi,

I'm having some issues getting stability in the GI using a pre calc'd method. We have fairly recently upgraded to 3.6 from 2.3 and have been testing various methods.

I know the recommended settings are now BF-LC but I can't get a fast enough render time to use in animations so if I apply the same workflow as I did in 2.3 I am finding some oddities.

My old workflow for static scenes would of generally been:

1. GI. First & Second bounce set to Light Cache. Single frame flythrough mode.
2: GI First bounce Irradiance Map, Multiframe incremental every 20 frame, Second bounce Light Cache set to from file
3. GI. First Irradiance map set to from file, Secondary bounce set none

Now if I turn of the secondary bounce in the 3rd stage I get render times are so slow I haven't even completed a frame yet. (at least 10x slower on a region).

Would that be expected?

thanks

[vlado]

How many lights do you have in the scene? Does it matter if you set the light evaluation to "Full evaluation" as opposed to "Adaptive lights"?

Best regards,
Vlado

[grasshopper]

There are about 75 lights and a sun in the scene, not very intense its a large double height space about 50x20 meters. I haven't tried changing the light evaluation but I'll give it a go now. I assume I'll need to precalc the LC & IR again?

[grasshopper]

Thanks for the input, That seems to have helped to a degree (and makes sense now that I have read the info on adaptive lights!) Render times are now only about twice what they are with secondary bounce set to Light Cache, I guess that would be expected.

The reason I turned it off is that I'm having flickering issues in the rendered frames coming from the GI. I think and hoped turning it off would solve it.

Any idea what might be causing it? Attached is a crop of the GI pass where the flickering is most obvious. http://www.chroma3di.com/uploads/03_Reception_GI.mp4

[vlado]

I don't actually see any flickering, but it might be my ipad screen. In any case, the tooltips for the light cache parameters have some suggestions to remove flickering (subdivs at 3000, retrace at 8.0).

Best regards,
Vlado