Cloud Flickering Problems

[l.a. akira]

Working on a BGs for a plane animation and im trying to figure out why im getting flickering in the clouds..

http://www.industryvfx.com/AL07_MD_BG_v003.mov

I've tried maxing out the GI relative detail and sample quality to 6 and 6.
Clouds are set to Accel cache none, 320 samples and enable rt shadows.
Thanks in advance.

[Volker Harun]

Turn off GI ... that might be it. And/or use a bit of motion blur.

[Insquall]

The global illumination looks to me to be the problem, but I don't think turning it off is a viable solution. Because the scene would be shaded incorrectly.

Try increasing the GI sampling quality, but lowering the relative detail. Maybe so the render time is the same as before.
(eg relative detail 2, sample quality 18)

My hunch is this should lower the flicker but decrease the amount of details in the GI, which you don't really need.

I only have the free version and I haven't done any animation tests. So anyone feel free to correct me.

Motion blur is on isn't it?

Edit: also you don't need raytraced shadows for the clouds in this scene. If I remember correctly they only affect the atmosphere being shadowed by the ground. And the clouds are above the ground

[l.a. akira]

Motion blur is set at .5 and the camera is pretty far above the ground so the blurring isnt very noticeable unless you are comparing it to still frames with no camera movement. Will try modifying the GI settings. Thanks for the input.

[Volker Harun]

Just for poking around ... Insquall ,-)
GI is known for its inconsistant outputs. So turning it off is the major point. If the shadows turn to be too dark, fill light could be used. ,)

[Insquall]

Ah yes sorry, you could use lights instead of GI

[bigben]

If you fly close to ground you might also consider looking at my fill light setup (just moved it to the files section - http://forums.planetside.co.uk/index.php?topic=1921.msg18762#msg18762). The two lights at the zenith provide a little extra shaping in some situations.  The lower lights are probably redundant for your application and could be disabled. 

Are you animating the clouds as well?

[Matt]

I agree with Insquall that GI sample quality is probable the best way to reduce the flickering, and that you can probably reduce the GI relative detail a little to cope with the increased render time. You can enter higher values than 6 if necessary.

Another thing that may help is reducing the "glow amount" and "glow power" in both the clouds and the atmosphere (but mostly the clouds in your scene), as these tend to increase variance in the captured GI.

Matt

[Volker Harun]

Hi Matt,
definetly you know it.
One question, is my way wrong?

Volker

[Oshyan]

Turning off GI entirely is the best way to get rid of the flickering but you also lose the nice qualities of GI of course. It's worth trying fill lights first IMO to see if they are an acceptable solution in a particular case because they will also generally render faster. Finding the right tuning of the GI settings may take a while and the render times are likely to be high as well. But if GI detail and quality are a vital part of the scene then such tuning will have to be done to find the right values.

- Oshyan

[Matt]

Volker,

Using fill lights instead of GI should eliminate the flickering, but if it's possible to eliminate the flickering by changing other settings then that is preferable if final image quality and realism are the most important things.

Matt

[Volker Harun]

I agree to the point of quality and realism.

Depending on the scene I would go for the least time intensive way, but. It is a tradeoff I would go for when rendering an animation.