Secondary Fragmentation on Clustered & Constrained Objects

[Farmfield]

To your defence, it's really not as simple to control spawning in TP or Pflow compared to Houdini - though there's a lot that is simpler in TP and Pflow than in Houdini POPs too, hehe... 1-1/2 years ago when I started out in Houdini, one of the first things I tried to set up was to rotate a particle around it's axis of travel (and I mean inside POPs, not after) - something I finally learned how to do like a month ago.

But back to this subject of the thread...

Constraints in Houdini can be really tricky to get it looking/acting like you want it too. For setups where you want clustering and that kinda sticky, flexible breaking, I believe a combo between glue and cone twist constraints are a good solution. The problem with cone twist constraints, though, is they haven't a breaking strength, so you gotta do a lookup on the constraint force and manually setup a dissolve/delete of those constraints in a SOP solver. That makes it really controllable, but it's not the most efficient in regard to tweaking the settings, but it is what it is, you gotta work around it.

And I have yet to find a good, reliable way to setup a split constraint system for clustering, that is using a higher strength to cluster pieces and lower strength between them. Though the problem seems to be more in the constraints solver than in setting it up, because even if I create a setup like that, it's really hard to get it to behave like I want it too - but then again, perhaps I'm missing something.

Another solution would be splitting clustered pieces in a SOP solver based on some rule. The clustering is done using the name attribute, so if you were to take a cluster and give it's pieces separate names, it'll be handles like separate pieces by the Bullet solver.

Something I have yet to try is doing do secondary fracturing in a SOP solver... Think how you'd set it up in TP, a rule shuffles a particle into a group, then you use volume breaker to fracture them, it's just an awesome way to do recursive fracturing. And you could set it up similarly in Houdini. The idea is, you do the initial fracturing in SOPs, feeding that into the sim. Then you setup a threshold in a SOP solver where a set hit value for a piece will unpack it and run a voronoi fracturing, repack the pieces and feed them back into the simulation. It should work for doing recursive fracturing. You could even set up a constraint network for the new pieces.

[Solitude]

14 hours ago, Farmfield said:

Something I have yet to try is doing do secondary fracturing in a SOP solver... Think how you'd set it up in TP, a rule shuffles a particle into a group, then you use volume breaker to fracture them, it's just an awesome way to do recursive fracturing. And you could set it up similarly in Houdini. The idea is, you do the initial fracturing in SOPs, feeding that into the sim. Then you setup a threshold in a SOP solver where a set hit value for a piece will unpack it and run a voronoi fracturing, repack the pieces and feed them back into the simulation. It should work for doing recursive fracturing. You could even set up a constraint network for the new pieces.

The 'make breakable' shelf tool does dynamic fracturing in dops. It uses the voronoi fracture nodes (dop nodes/sop solvers) to make it happen. The setup is 100x easier in TP if you were building it from scratch. 

[Farmfield]

Disregarding the complete control you have in Houdini, or rather the methodology that enables that control, the workflow in Thinking Particles is truly brilliant. In TP I exactly know how and in what order the data is handled, in Houdini DOP's, after 1-1/2 years I still don't understand completely how the data flows through the network, the order of calculation, so to speak - and it messes with my mind sometimes. Well, at some point I'll get it, hopefully.  

And I use the shelf stuff extremely sparsely and if I do - for creating setups - it's mostly to see how the SESI guy's set it up. My default approach is to come up with a solution, set it up and see if it works and if it does it now becomes about simplifying it as much as humanly possible, then start tweaking it. And if I need to set something up, if I know how, before using the way I know I try to come up with another way to do it. Because Houdini.

For me this is like playing with Lego's, the fun isn't in building stuff from blueprints, it's just playing with that huge pile in front of you and see where it leads.