Bird Poop

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  06 June 2013
Bird Poop

So dont let the title fool you, this is serious shit (pun intended).

I am trying to make bird poo. All i need is for it to source from out of shot, and fall onto an object, landing on it and slowly rolling down.

I thought this would be fairly simple to set up using fluids, but after several hours it gave me the shits.

I setup a simple 3D fluids container, used mostly default settings, negative buoyancy, and surface rendering to create a sort of tap like effect. This worked great until i started playing with the emission. When i animated the emission rate, to only emit for say 5 frames to create a small burst, the fluids start disappearing. I though that it might have been the dissipation attr, but that is set the default 0.

Is there something i am missing? Is there another way to go about this?
Any help would be greatly appreciated, help me finish this crappy job
  06 June 2013
This sort of thing is easier with nParticles (see attached scene). One can create an nParticle emitter (start with the balls preset) then create a component to component constraint. On the constaint modify it to use connectionMethod= maxDistance and set the max distance to a few times the particle radius. Make the emitter a volume emitter so that the particles don't all originate at the same spot and scale the volume. Also on the particle increase emission overlap pruning to keep particles from emitting too close together( otherwise the max distance constraint attempts to hold the particles closer than their collision distance which causes them to explode outwards ). The Max Distance constraint reforms each frame creating a viscoelastic fluid.

Then just convert to poly and play with the particle meshing attributes.
Attached Files
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  06 June 2013
Thank you so much Duncan,

That should give me an excellent place to start tweaking things. Just a quick question, i just had a quick play around, just wondering what would the best way to make it flow a little free-er. Say more like liquid?

Thanks again.
  06 June 2013
For a more free flow you could lower the constraint strength a bit and perhaps lower friction on the particles. Perhaps lowering collide strength might help as well. Or you could try turning off self collisions and enable liquid simulation. The liquid simulation will not lock and be as hard as normal self collisions and can compute faster. You need to more carefully manage the collision radius values and things like the like the liquid radius scale. As well overlap on emission can cause particles to explode outward, although that simulation already uses emission overlap pruning. The blobby radius and threshold are also useful for getting a smoother more fluid look.
  06 June 2013
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