debris creation... how you doo

[nFrame]

Hey Guys, I'm working on some debris sims at the moment, and I thought I'd try to pick a few brains on the setups and techniques you use.

It seems to me, that the "Debris" shelf tool calculates a bit slow, and while I fully don't understand the different connections it's drawing between different contexts yet, it sure seems practically unusable. But the idea of what it's doing makes a lot of sense. Is there a faster way of the same technique?

I've attempted to create my own debris system using something similar to the cmiVFX houdini debris systems setup, and it looks fairly good and sims fairly fast, the collisions are particle based and obviously don't respect the debris I instanced to them. I think this technique works fairly well for distant debris, but certainly not hero stuff.

I've also attempted sourcing rigid bodies from emitted particles, and letting DOPs handle the collisions. This was slightly tricky to get the collisions playing together nicely when the rbd's are created against the already cached collision sim, and while it ultimately made for a better look in some cases, it certainly isn't a very fast sim.

So I guess i'm just wondering what other people are doing? are you using particle based debris, or RBD's debris? or both? how are you creating them? what are your caching dependencies you create with your workflow? are you creating elaborate scaleable systems, or are you giving things absolute values and frames?

thanks for any info, I think this could be very valuable to a lot people ")

[nFrame]

this is somewhat troublesome. Either people just aren't creating debris for their sims, or they're not willing to share their techniques.

teach a man to fish, *wink *wink

[Marc]

To be honest there is no one answer. All of your techniques listed are perfectly valid. I would say that there isn't one best technique, but use the best one for the shot you're trying to do. Particle debris is perfectly acceptable if you aren't going to see per debris collisions. If you are then you have to do a rigid body sim. How you generate your debris pieces will also depend on what kind of effect you're doing. Sometimes fracturing on the fly works, sometimes prefracturing your geometry and building glue networks to control the breaking will be what's needed.

In some shots we did recently the bulk of the debris was particle based except for pieces close to camera, then we did hero sims for those. But that only worked because of the very specific type of shots we were doing.

This is where a good lead/sup/senior will come in to help determine what would be best in the situation. If you're doing this on your own, then posting to odforce will help, but you're probably going to have to be specific in what you're doing and what you're hoping to achieve.

That's a really long winded non answer I know . Hope it helps in how to think about it though.

M

[pclaes]

*) if it is debris, it should be small so you "feel" it, but you can't actually see it (motionblur), if you are supposed to see the pieces tumbling as they fall over another surface it becomes rbd.

-- you can fake the rotations based of the length traveled and your orient quaternion when using particles. Otherwise use small cubes.

*) debris is particles - generally in dops so they can collide with the already cached sim

Sourcing happens generally when my big rbd sim has been simmed to disk. The dopimport stores the position and orient on points. That is applied to the pieces in their rest position through a lookup attribute. Once you have the lookup attribute you can transform all kind of things, either the original geo, higher ressed geo, a pointcloud representation (which you can use to trigger your points from), or a volume representation. - I've covered how to set up some of this stuff in various posts here on odforce and on sidefx forum. You can use the advanced search with my username in it.

Also I am making some tutorials on this stuff because it keeps coming up.

[nFrame]

Hey Guys, thanks for the replies, this thread got kinda buried.

Peter, I've seen a bunch of your posts on the topics you mentioned here, and I had a few questions specifically to swapping low res geo for high res geo after simming. It's a very obvious process using the copy sop, and works great with the same # of pieces obviously (also discussed in other threads, I know) But I'm very interested in how to create the relationship between a lower number of lowres sim objects, and a higher number of highres objects. It seems like a matter of determining which highres pieces should belong to which lowres piece based on proximity(?) and through this, assigning the corresponding lookup attribute to link it's SRT to the low res sim. please correct me if I'm misunderstanding ")

Best!

[kurtw]

It depends, but most of the debris I've done on shows is a combination of modeled objects driven by particle motion and RBD's, combined with some particle elements [small bits of secondary particulate motion] and some volumetric dust layered in.

On one show we tried reusing the parts library from a sci fi show that was in production at the same time, we got busted because it wasn't period correct for the film I was on. Production green lit us to run over to turbosquid and we picked out some junk we could throw around in our scene and the problem was solved.

Now if its debris destruction of a prop/set piece, then there is some more modelling work, ranging from model swapping and having some hero sections that are broken apart then adding some procedural chunks created by voronoi with noise, etc.

Problem is you can often spend a fair bit of time trying to make voronoi .. look.. like not voronoi but something more natural looking.

I'd like to see a FEA setup for houdini, FMM for Maya/Max by pixelux is a handy toolset at an amazing price [$299] I've been playing with that in a demo version, Not used to working with maya these days but I guess one could write a otl that connects to maya with the FMM plugin via python Hmmm.

Edited March 18, 2013 by kurtw

[Netvudu]

when you say FMM, you mean DMM, right?

I was pretty impressed by DMM on a first contact with the demo version (BTW, really LOW on Autodesk to sell it as a new feature when it was just a demo). Later attempts on true production quality left me pretty disappointed about the lack of control I was given and the speed was really low. Of course, it was pretty cool to have soft and hard deformations at once, but still I was a bit disappointed. Maybe I´m spoiled by the amount of control Houdini gives.

This was a year ago, though, so things might have changed.

Edited March 18, 2013 by Netvudu