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SiRpRoHxO
Hi,

I'm working on a bloostain, that shall diffuse/expand over 450 frames to fill up the whole frame in the end (to be used as a kind of 2d transition effect later on)
I was able to do a nifty flip sim, but in the end it wasn't behaving like blood at all.
To get more of that blood-like rolling diffusion effect, I tried to introduce some viscosity. But with viscosity on, the stain isn't moving anymore.
(The bloodstain should already be there, so no dripping & dropping, only expansion in x and z)
Tried different viscosity-values, played around with friction and vel as well, still no luck.

I think some viscosity could help here, so can someone point the right direction to get it to work?
I`ll attach my try
thanks in advance
mrCatfish
I haven't rendered it yet, but with your sim I took out the POP attracts, took you existing point velocity and multiplied it by 25
@v*=25;
, plugged in a POP wrangle with
@P.y*=.1;
, and turned on viscocity and “Slip on collision”. When surfacing, I smoothed it out a lot, and it's looking pretty cool. It might be splashing too high in Y, but you can post-sim scale this down.

EDIT: Rendered it and it is indeed not looking sticky like blood.
mrCatfish
Did you try to use the POP fluid node? I've been playing around with that and it's a million times faster and it's already looking a lot more like blood. I think the biggest problem is I assume you want it to get bigger and bigger, and it's just going to turn into a blob eventually. Is it supposed to be a splatter or a spreading pool?
SiRpRoHxO
hey, thanks for your effort.
In the meantime a came up with ‚ÄúSlip on collision" aswell, set it to 1 to get an effect but yeah… not really bloodlike unfortunately.
The blood shall not splatter at all, just spreading till it fills all corners.
Didn't tried the POP fluid yet, but thats worth a try.
SiRpRoHxO
All right, I tried POP fluid and it works very well for that use case.
But at a certain point in the timeline, holes appear on the surface and I don't know how to fix that.
Is there some kind of reseeding option for POP as well?
SiRpRoHxO
ok setting constraint stiffness to 200 seems to fix.
(atleast for the first 200 frames as yet)
SiRpRoHxO
hmm seems the pool gets slower and slower and nearly comes to rest at around frame 250.
Any way to keep it evolving?
mrCatfish
You can grab some velocity from another object at SOP level with a POP wrangle and pcopen. Check out attached file and look at the “keep_going” POP wrangle… you can animate the “boost” channel to increase the velocity when it start to slow down.
SiRpRoHxO
thanks, that helped a lot.
Its a smart way to reintroduce some vel back into the system.
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