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Popping / Shaking Artifacts with Whitewater


ianoreo

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On 6/17/2021 at 1:07 PM, sipi said:

My guess is Adhesion, under Foam tab. Do you have it enabled? If so, try to disable it first:

image.png.3478c35aa74a8044a326c1801098015d.png

Disabled it and definitely better-- but still seeing these flashes within the density of the foam itself? Attaching an actual render as it's a bit clearer there than in the flipbook. It's almost like the density is rapidly turning on and off across the surface area of the whitewater.

I tried playing with the chramp value ranges in the set_density wrangle post-sim but not much luck there.

thanks for your help!

densityJitter.mp4

set_density.png

Edited by ianoreo
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Try this: ignore this set_density Attribute Wrangler and set a constant @density value like 0.01 and see what happens. I usually don't use this set_density Attribute Wrangler created by shelf tool because sometimes I experienced jitter from that as well. I don't really have any other idea.

Edited by sipi
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7 minutes ago, sipi said:

Try this: ignore this set_density Attribute Wrangler and set a constant @density value like 0.01 and see what happens. I usualy don't use this set_density attribute wrangler created by shelf tool because sometimes I experienced jitter from that as well. I don't really have any other idea.

Yeah, tried that-- definitely being caused by that node (or data that node is using). I tried simplifying the node a bit to weed out the problem variable... maybe it's @depth?

set_density_change.png

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7 minutes ago, sipi said:

It could be... I think it worth a render with just a constant @density value.

True-- just lose a lot of the finite detail that way :/

My solution at the moment (which is also causing a lot of loss of detail), is just blurring the hell out of the @depth value haha!

depth.png

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8 hours ago, ryew said:

Is this only occurring where the whitewater is hitting your collider?  Does your movie contain both bubbles and whitewater and is there a transition between the two?  Hard to tell

There is definitely a concentration of flickers at the collision edge for sure-- why would that be an issue you think?

Just using an inverted sign sphere as collision.

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It's why I was asking whether you are using a bubble<->whitewater logic in your network, to find out if this happening because certain particles are slowing below a particular threshold and flipping back and forth between states.  I dealt with a situation like that previously and wound up culling particles within a certain threshold of the colliders (vdb dilation for grouping in a sopsolver post-sim and then deleting by id)

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6 minutes ago, ryew said:

It's why I was asking whether you are using a bubble<->whitewater logic in your network, to find out if this happening because certain particles are slowing below a particular threshold and flipping back and forth between states.  I dealt with a situation like that previously and wound up culling particles within a certain threshold of the colliders (vdb dilation for grouping in a sopsolver post-sim and then deleting by id)

Ah I see! Pretty much just shelf tool Whitewater setup. Disabled adhesion but that's about it!

Maybe should have a play with a culling approach as you've mentioned.

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Culling is at least a quick troubleshooting check to see if the issue is isolated at your collision surface. 

If you've already identified the density expressions as the source of the trouble as mentioned earlier in the thread, I'd suggest isolating a set of particles in the cache that is popping and trace their density values back through your expression logic.

Edited by ryew
typos
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