I'm trying to make a stream of money (bills) flow into a toilet.

A metaphor for our times :/

I've created several low poly bills and grouped them for a particle system. I've created a particle system and have the bills streaming out. I can get the bills to collide with the toilet: some go in, some go out, that's fine. But the bills are stiff, do weird things when they collide with walls, and they all rotate/move from their object origin rather than collide with corners/edges of the bill. They stick in the floor upright from the origin: they rarely lie down :/

I don't know how to apply the cloth simulator to either the paper objects or the emitter.

File here: https://www.dropbox.com/s/sfr5pxfgn8uo681/toilet.7z?dl=0

  • $\begingroup$ I feel like this could be achieved using a cloth sim and wind. You may not need them to be particles. $\endgroup$ – Mentalist Oct 28 '15 at 0:43
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    $\begingroup$ @Mentalist : If I did that, how would I create a constant flow of cash? Wouldn't 1000 individual bill objects being blown around be more taxing on the comp than a particle system? $\endgroup$ – OroNZ Oct 28 '15 at 22:16
  • $\begingroup$ Maybe. In these cases it's best to do some rough tests and see which method seems most effective. There is a way to direct particles with forces, and I was looking for the tutorial vid for that. I haven't been able to find it, but I did find another one that looks very relevant to your project. Haven't watched this yet, but in case it helps: How to animate realistic falling leaves in Blender. $\endgroup$ – Mentalist Oct 29 '15 at 1:23
  • $\begingroup$ Found it! This is the tutorial I was first thinking might help you. "Curve Guide Force Field" is what it's called. It can help you steer all of those bills right into the toilet if you want. ;-) $\endgroup$ – Mentalist Oct 29 '15 at 12:26
  • $\begingroup$ @Mentalist: I have seen a couple of tutes on particle flow direction using curves. Directionality isn't what I'm after. Cloth simulation acting on particles is the key. The linked tute, while handy, doesn't address either cloth sim, or multiple cloth objects being directed by curves. It's the 'clothiness' I need to apply to my particles, not a particle path. $\endgroup$ – OroNZ Nov 2 '15 at 1:39

With the cloth simulation, you want to select your dollar bill object and go to physics tab; it's in the Properties window under the Outliner by default, same window you go to for your particle systems. The icon is a bouncing ball. If you can't see it, over over the panel and scroll until it's in sight, or enlarge the window. Hit the cloth button. You're going to want to play around with the stiffness setting in particular. You don't want it to act like a dollar-printed hankie. Once you have setting to work with, you'll need to let it run it's simulation. You'll probably do this several times until you get something you like. After you're finally satisfied, bake all your dynamics.

Go back to your particle system; make sure you have gravity on. Mess with the weight values; your money could just be too light. Finally, apply the bill's orientation so that the origin is in the middle of the bill, and it lays flat on the floor by default. That part should help with the standing problem, at least.

  • $\begingroup$ I suggest you do everything you just said on the .blend file I supplied. I have 40kg bills that won't lie down. Often they just jiggle around, on an edge or on a corner. Most of them ricochet off toilet edges. The default orientation of all bills is flush with the floor. Nice try, but this hasn't solved my problem. $\endgroup$ – OroNZ Nov 5 '15 at 11:54

I've tried several ways to try and combine physics systems to get around this problem, and none have been successful. I can get cloth simulation happening. I just can't get cloth PARTICLES happening.

I can get Soft body physics happening instead of cloth sim., but the bills don't want to lie down.

I'm still clueless on how to fix this, and I'm not sure if it can be solved at Blender's current stage of development.


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