Houdini - Fast chain simulations

download .hip and .hda files at: / fchamon
How to procedurally model chains from curves, and how to simulate them in the most efficient and stable way using sphere collisions and the bullet solver.
00:00 Single chain link model
02:16 Sweeping links onto curve
05:12 Creating the collision geometry
11:04 Setting up the RBD sim
11:50 Tweaking sim parameters to get good results
13:55 Transforming the original chain links with sim results

[@isstuff]

This is close to what was used on the movie “love and monsters” we had a huge crab on a chain. The chain links were made of a line making the extended circle and a sphere copied to the points on the curve making an overlapping string of pearls. This made for a less bumpy simulation surface. The rest is mostly the same.

[@rennightmare]

might be the best approvement of the tutorial usability to know that same technique was used in film production

[@PeterKLee]

amazing work! thank you for sharing useful tutorial!

[@ibrahimsojiv88]

We need more ❤❤❤ tutorials

[@SoriVFX]

Thank you so much :D

[@VuPhamRainstorm]

thank you

[@user-rh2su6lx6x]

what! no constraints?! that is so mind blowing!

[@khichastudio465]

4:54 My chain doesnt fit properly when I use a new curve, The rotation is completely messed up.

[@cadian_music]

what a great video, in houdini 20 the sweep node is different, i saw suggestions to use copy to points instead but it does not allow the chain links to be oriented along the curve, they just keep their original orientation. Is there any way to work around this? Thanks!

[@fabricio_chamon]

Hi, yes use copy to points now! And right before the copy to points node add a "orient along curve" node to make the links follow the curve direction.

[@LeeHongRestaurant]

Yeah, and to rotate the chain link need apply Roll or Twist inside the Copy to Curves Node. If try to use transform node like in the video now can be problematic I think.

[@cadian_music]

Thanks a bunch for the pointers! I ended up downloading the HDA and taking it apart to see how everything works, got everything working now and running chain sims for days!!

[@Francis-yc9nc]

You can Select the old sweep in Houdini! Window Top Toolbar -> Assets -> Asset Definition Toolbar -> SELECT show always. then in the Sweep Node Parameter Tab you can change to the old Node.

[@vicg.a.2526]

Francis you just saved my ass. Thank you so much! @@Francis-yc9nc

[@jim754]

Hi, Thanks, it's fast. But Some crosses generated after sim. Is there a way to create perfect sim except add the sphere of vdbtosphere node(To Infinitely close to the surface of mesh)?

[@wewatchtheskywaiting]

Thanks ! approche for RBD, but I don't get the sweep node part as you get 3 inputs on it, if I plug as it on the actual node in 19.5 (2 inputs) line a a torus for ex.I don't have that king of copy to point effect you achieve... even with a 1 on 2 points group by range before ... do I miss something ?

[@jonathanlavanant]

Use copy to point instead :)

[@rachelzenzile]

If you add a convert node after the VDBtoSpheres, switch it to polygons, that'll get it to work and also keep the attribute name.

[@portmantologist]

I'm trying to follow along in 20, and having some of the same troubles. The first thing is to switch surface type in the sweep to Rows instead of Quadrilaterals. AFter that, @rachelzenile appears to be right about converting the spheres to polygons, either increasing U and V in level of detail or switching to divisions per span.

[@ericaxelson5632]

This all works until the chain has a bit more complex shape. Tried with a helix shape with more turns and the sim breaks straight away even with very high substeps. A simple shape like a line seems to work fine thou.

[@fabricio_chamon]

Nowadays I'd just use less spheres with larger/intersecting radii, that should give you more stable links without increasing substeps too much. In any case, I'm curious to see the helix shape you are mentioning, as this approach should be robust enough to handle more than simple lines.

[@ericaxelson5632]

@fabricio_chamon Sorry i forgot this, i figured it out. it was just a silly error. when creating the curve shape and you have a large enough chainlink the link intersects from the start. stupid of me but yes, your solution works really good!