Flickering trees and shrubs

[jonasa]

Hi all..

I know there are zillions of posts with similar subjects, but most seem to focus on anti aliasing. We have done some testing with our scene which has shrubs made from PArray's - and the flickering seems to be related to the GI settings rather than the AA.

Our scene is a simple exterior with only a Vray Light as direct light source (have also tried VraySun and normal target direct.) Shrubs are flickering badly - but only with GI turned on.

We think need more GI detail - specially in the small geometry of the leaves. Question is what parameters will make most impact on the detail.

Reading the manual, suggests these parameters:
HSph. Subdivs (we have the default 50)
Interp. Samples (also default 20)
Nrm Thres. (0.1)
Dist. Thres (0.1)

[Joost Ink]

What GI solution do you use?
I can recomend for these kind of scenes:
LC+QMC
and for AA Adaptive QMC

[Joost Ink]

Also...
is the geometry ok? no double faces? What mat did you use on them?

[joconnell]

Heya!

I did a fly through of an orchard right down into the trees over 200 frames and it's been the most irritating shot I've ever done. If you get the gi totally perfect, depending on how quick you move and what size the leaves are in frame you may get flickering from the leaves themselves - purely cos they're so small and different due to their angles / colour / specular. If you're going the GI route, try baking the GI so it can't flicker. You don't get a lot from the second bounce if you're above the trees so even consider using a dome of really soft spots as a skylight and some weak omnis under the ground to get a single bounce on the light. Next and probably most important thing after that is motion blur. In my case I used the smudgy post motion blur which helped a lot - it blended over the leaves which helped my flickering and also smeared out some of the graininess.

It's a tough one to do since you're fighting against broadcast limitations too.

[joconnell]

Of yeah - definitely no opacity maps on the leaves - they'll murder you.

[sv]

I did a fly through of an orchard right down into the trees over 200 frames

Was it for an advert by any chance? A Cider advert?

[jonasa]

Cheers guys...

No double faces - for sure
Might give LC+QMC a go, probably the only combination we havent tried except for photon mapping.

No opacity maps - onyx trees geometry only and PArray shrubs (static).

Might consider a dedicated (nonGI) light rig for the trees and shrubs

Would the Detail enhancement solve this? or just extend rendertime?

Wish it was possible to tweak the GI settings to achieve this

[Joost Ink]

ah, did I say LC+QMC I meant IR-QMC, sorry.

[joconnell]

I did a fly through of an orchard right down into the trees over 200 frames

Was it for an advert by any chance? A Cider advert?

Yup - four of them. I didn't do the first in the series, I did the summer, autumn and winter ones - magners / bulmers. Wasn't really happy with them to be honest - the production company shot loads of footage from different lenses at different times of the day and wanted all of them in the same shot and then our trees to match those shots and the next shot they blended into - bit of a nightmare really...

[Da_elf]

my default for IM is always 60/30 0.3/0.3/0.3

[unknown]

try using a dome vray light for your shrubs, and comp them over the base frames. works a treat. that way it never flickers. Just a few colour corrections and away you go., you can also add a few spots under the scene to brighten the undersides old sckool stylee.