GI flickering with BF+LC

[seq]

Hi Vlado,

did you have some time to look at the scene? It really seems that the opacity (when mapped or smaller then 1) is the reason for all of that.

Can you confirm that?

Thanks,
Lars

[vlado]

Yes; it looks like it has nothing to do with the curtains; there are two things in your scene that cause the flickering:

1) The "Time dependent" option for the DMC sampler in the System tab is turned ON, which means that V-Ray will generate completely different samples for each frame;
2) The camera FOV is animated. This also causes the samples to be different from one frame to the next.

Best regards,
Vlado

[seq]

Hello Vlado,

thanks for your reply.

If I remember correctly we get some strange results when we turn off the "Time dependent" function. The noise of the image begun to "swim". But we check that again.

Hm, if we can't animate the FOV that would be a big disadvantage. How can we change the camera FOV like you would do with a real film camera?

Best regards,
Lars

[vlado]

If I remember correctly we get some strange results when we turn off the "Time dependent" function. The noise of the image begun to "swim". But we check that again.

You are right, it will lock the noise for the brute force GI too. That's why I said that I will probably need to disable it internally just for the light cache.

Hm, if we can't animate the FOV that would be a big disadvantage. How can we change the camera FOV like you would do with a real film camera?

It can be done in two passes - one pass where you first calculate the light cache for each frame with a fixed FOV, and the second pass for the actual rendering with animated FOV. I will have to modify V-Ray a bit to support per-frame light caches though (both for reading and for writing).

Best regards,
Vlado

[seq]

Hi Vlado,

can you add the first solution for a NB or do you need more time to do it? Would be a help for our current project.

And for the second: Is this also true if we animate the F-number, Shutter speed or the ISO? And which Focal length setting would we use for the LC calculation?

Any chance that the per-frame LC caches will become true in the near future?

Thanks
Lars

[johnszot]

hey Lars -

i know this is an older thread, but i was wondering what your per-frame render times looked like when you set the DMC noise threshold at .002....
also, what resolution were you rendering at?

thanks

- john

[seq]

hi john,

at the end we used these settings for the animation (960 x 610 Pixel):

Image Sampler: Adaptive DMC, Area 1.5
Adaptive DMC: 1 / 10 / 0.009

Brute Force: 16 / 8

Light Cache
16 / 1800 / 1.5
World Scale, Store Direct Light off, Adaptive sampling, Use camera path on
Filter type: Nearst
Prefilter: 100
Filter samples: 50
Use LC for glossy rays off
Single Frame

DMC Sampler
Adaptive Amount: 1
Adaptive Threshold: 0.06
Min. Samples: 6
Subdiv. Mult: 1

Render times between 10 and 15 minutes.

Hope this helps
Lars