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Animated volumetric light flickering

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Jared Flynn
Animated volumetric light flickering
on Mar 28, 2013 at 10:35:16 pm

Hey folks! Another puzzle for the hive mind.

I'm working on a scene in R14 Studio with a volumetric light that's moving along a path from frame left to frame right, spilling light through several objects as it moves.

Unfortunately, at render time, I'm seeing a TON of flicker in the beams of light, and I can't for the life of me figure out how to fix it.

I've tried considerably reducing the Sample Distance under the Light Object > Visibility settings, but it doesn't seem to be making a difference.

The real thing of it is that I absolutely conquered this exact issue a bit over a year ago, but I seem to have misplaced the project. I remember learning that the flicker was coming from however the volumetric light is calculated-- by continuously changing the position of the light source, the volumetric effect has to be recalculated from scratch every frame, creating flicker. There was some setting somewhere in the wide world of C4D that allowed the volumetric effect to be calculated with a finer precision, but I can't remember where to find it.

I've attached a scene file that mimics my situation in case anyone wants to have a look. The Sample Distance of the light in this scene is set to 0.5cm, down from the default 25cm, and at any spot in between the flickering is still present.

5731_jfflickeringvolumetric.c4d.zip

Any insights greatly appreciated!

Thanks so much in advance,

Jared Flynn
Motion Graphics Designer
http://be.net/jkinetic

Supermicro SuperWorkstation 7047A-T
Dual 8-core Xeon E5-2670 @ 2.6GHz
64GB DDR3-1600 ECC/REG RAM
PNY nVidia Quadro 4000
Windows 7 Pro 64bit SP1


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Adam Trachtenberg
Re: Animated volumetric light flickering
on Mar 29, 2013 at 3:11:26 pm

The only thing I can come up with is to use subframe motion blur to average out the flicker.


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Jared Flynn
Re: Animated volumetric light flickering
on Mar 29, 2013 at 4:11:49 pm

Thanks Adam!

I was thinking about that too, but it's definitely not what ended up solving the problem the last time I ran into this...

I did some more checking and actually found my old scene file, which totally works although an overview of the various settings still leaves me stumped as to what I was doing differently.

Placing a new light in the scene I dug up, I'm finding that the flicker is still gone in the old light, but is present in the new one. I compared their settings and they're virtually identical as far as I can tell.

Duplicating the "good" light produces another "good" light. Merging a scene with a "good" light into a new scene also seems to keep the "good" light acting properly. So strange!

Thanks as always for taking a gander!

Here's a reduced version of what I found in case there's a discrepancy I missed.

5738_jfvolumetricworkingcomparison.c4d.zip

In the meantime, I'm hoping I can just piggyback on whatever moment of genius I had a year ago and just use the "good" light in my new scene... we'll see how it goes.

Jared Flynn
Motion Graphics Designer
http://be.net/jkinetic

Supermicro SuperWorkstation 7047A-T
Dual 8-core Xeon E5-2670 @ 2.6GHz
64GB DDR3-1600 ECC/REG RAM
PNY nVidia Quadro 4000
Windows 7 Pro 64bit SP1


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Adam Trachtenberg
Re: Animated volumetric light flickering
on Mar 29, 2013 at 4:38:32 pm

Huh ... I'm stumped. You had colored falloff in the noflicker light's details tab, but copying that setting over made no improvement in the flicker light. Might be one for Maxon's tech support team.


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Jared Flynn
Re: Animated volumetric light flickering
on Mar 29, 2013 at 6:06:25 pm

Isn't it weird? I can't seem to figure out what I possibly could have done here, but I distinctly remember the "a-ha" moment last time around.

I'll send the question over to Maxon and hopefully they'll have the solution-- if so I shall be a good forum user and post their findings. :)

Thanks again!

Jared Flynn
Motion Graphics Designer
http://be.net/jkinetic

Supermicro SuperWorkstation 7047A-T
Dual 8-core Xeon E5-2670 @ 2.6GHz
64GB DDR3-1600 ECC/REG RAM
PNY nVidia Quadro 4000
Windows 7 Pro 64bit SP1


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Jared Flynn
Re: Animated volumetric light flickering
on Apr 2, 2013 at 12:52:45 pm

Just a quick update on this--

I've been going back and forth with a rep from Maxon and apparently we're all a little stumped. He was able to replicate the non-flickering light's settings with a new light, which didn't seem to flicker, but when he compared the two lights, a few properties (such as Radius/Decay) still inexplicably report "Multiple Values."

The only additional thing I was able to bring to their attention was that in the job where I got this thing working, I'd been using a previous version of Cinema-- either R12 or R13. I'm not sure, but it could be that the relevant property was moved/changed/removed with more recent releases, but for some reason the effect still works in an old project that's promoted to the latest release.

I think I've brought up a pretty good puzzle for these folks, hopefully they're able to help get to the bottom of it!

If I learn more I will keep this thread alive.

Jared Flynn
Motion Graphics Designer
http://be.net/jkinetic

Supermicro SuperWorkstation 7047A-T
Dual 8-core Xeon E5-2670 @ 2.6GHz
64GB DDR3-1600 ECC/REG RAM
PNY nVidia Quadro 4000
Windows 7 Pro 64bit SP1


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Brian Jones
Re: Animated volumetric light flickering
on Apr 2, 2013 at 4:40:51 pm

thanks for the update Jared


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Adam Trachtenberg
Re: Animated volumetric light flickering
on Apr 2, 2013 at 6:12:48 pm

Thanks for the update. I think you're right. Something was probably changed in the basic properties, but they kept some of the old code to maintain compatibility with older scenes. Hopefully your report will help them fix it in a future update.


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Christian Scheck
Re: Animated volumetric light flickering
on Jun 13, 2013 at 10:10:01 am

Hi Jared,

just came across your issue because I struggled with the same problem.
I found out that the only way volumetric shadows are calculated in C4D R14 is Shadow Maps (can't check previous versions). Whatever you choose (Raytraced, Area...) in the end you always get Shadow Maps. So if you switch your lights to Shadow Map and look at the settings, the flickering light has a resolution of 250x250 and the non-flickering light 1000x1000. That's the settings that are utilized, despite of what you set up in the Area or Raytraced tab.

Cheers,
Chris


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Jared Flynn
Re: Animated volumetric light flickering
on Jun 13, 2013 at 2:55:02 pm

Chris! You're a hero!

I just tried it out-- changing the FLICKER light's shadow type from Area to Shadow Maps, cranking the Shadow Map size up to 1000x1000 and the Sample Radius up to 8. Then I set the shadow type back to Area just for fun. Lo and behold, the volumetric light is flicker-free.

This definitely explains why I was so sure there was some setting referencing "sampling" that solved the problem before-- I believe in conjunction with the shadow map resolution, that "Sample Radius" property is a big part of the solution. Who knows where that insight came from the first time around.

In any case, thanks a million for sharing your solution, Chris! I'm going to re-open my ticket with Maxon presently and let them know (they were just as stumped, it seemed). Perhaps in a future release they'll break those options out in a more intuitive way.

Cheers!

Jared Flynn
Motion Graphics Designer
http://be.net/jkinetic

Supermicro SuperWorkstation 7047A-T
Dual 8-core Xeon E5-2670 @ 2.6GHz
64GB DDR3-1600 ECC/REG RAM
PNY nVidia Quadro 4000
Windows 7 Pro 64bit SP1


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