DOPs excruciatingly slow?

[tigakub]

Hi everyone! I've been trying to do some simulations in DOPs and have been getting disturbingly slow sim times. I don't think I'm doing anything too complex. One I'm just doing a simple cloth sim with a 20x20 grid pinned along one edge, and a gravity force. That's it. This is taking 3 or 4 seconds per frame to sim. The other is a bit more involved. I'm using Make Breakable to autofracture a box (10x5x0.2 ... i.e. a pane of glass) and then I break it with a passive sphere. This takes about 10 minutes to sim about 96 frames.

I've tried this on two different platforms: an oct-core 2.94GHz Mac Pro with 64GB ram and a Quadro FX 4800 running 10.6.7 and Houdini Apprentice HD 11.0.657

and a single i7 x980 3.33GHz with 24GB ram and a Quadro FX3800 running Ubuntu 10.10 and Houdini Apprentice HD 11.581.

At first I thought it was just the Mac, because Mantra on the Ubuntu runs circles around it (sometimes 5 times faster), but when the Ubuntu box took about just as long with the sims, I started to wonder. Is anyone having similar issues on Windows? Is this perhaps an OpenGL vs DirectX thing?

It's really strange because Cinema 4D (please don't scoff ) on my puny little MacBook Pro burns through cloth and fracture sims like wildfire. Of course, its tools aren't as sophisticated, or allow as much control, which is why I want to use Houdini. But waiting so long to see the results of sims really bogs down my work-flow.

If it's just a matter to migrating to Windows, I guess I could dust off my Windows 7 install disks, but I was REALLY hoping to avoid that.

[lukeiamyourfather]

I don't think the speed is an operating system issue. All of the tasks you mention use only a single processor for most of the time and cloth is not one of Houdini's faster solvers. There are some things you can do to optimize the simulation though like cache out SDF collision data for objects and simulate with a ROP geometry driver or DOP file node so it doesn't update the display as it simulates.

[symek]

I'm afraid this is how Houdini handles simulation duties... steady forward . I also wouldn't recommend its cloth solver to anything related to cloths... albeit it's handy for simulating deformations etc.

As to fracturing & RBD as I understand, Cinema4D offers some blend of Bullet and own stuff? If that's a case, Houdini does pretty much different work here, it actually simulates accurate fractured shapes during simulation. Bullet uses collision proxies. It can be useful for some cases, in other it really sucks...

As a side note, let me express my general astonishment on how people can live with bullet inaccuracy. I can imagine how useful this can be in massive simulations, but in any close up shot, with less then a few dozens pieces, bullet turns your animation into video game. At least this is my experience with Bullet. Houdini's RBD can be as accurate as you want, with controllable shape resolution and solver supsteps. This comes with a price, it's not super fast, which I consider neglectable, as in a real world it really doesn't matter (waiting a minute or five - more time you waste debugging your sims anyway). The problem starts with massive sims, where Houdini's RBD simple can't make it, and this is a room for ODE and Bullet solvers companionship.

skk.

Edited May 14, 2011 by SYmek

[tigakub]

Thanks for your replies. I do like the result of Houdini's breakable, although, I've had to wait quite a while to be able to see it. ;P

Yeah, Cinema 4D is quick and dirty. I wouldn't use it to do glass shattering in bullet time, but if I need something to break apart fast or at a distance, it gets the job done. It's cloth isn't the greatest either ... kind of a poor man's cloth.

Ugh, looks like I might have to go into nCloth. Yuk. I like Maya about as much as I like a pick axe in the ear.

[pgrochola]

SYmek - less than a few dozen pieces? Really? How often are you doing those kinds of simulations now days?!

I think it's a crying shame that SESI don't support bullet in Houdini. It's becoming the standard for a lot of the big studios, and for good reason! I'm using bullet in sops to get through a sim with 30,000 convex objects PLUS 120,000 implicit spheres. Can DOPS get through >1,000 objects? Is DOPs getting a bit outdated? a bit slow and overly complicated?

Now cinema 4D has it.

Please SESI make bullet in SOPs a standard!

Thanks for your replies. I do like the result of Houdini's breakable, although, I've had to wait quite a while to be able to see it. ;P

Yeah, Cinema 4D is quick and dirty. I wouldn't use it to do glass shattering in bullet time, but if I need something to break apart fast or at a distance, it gets the job done. It's cloth isn't the greatest either ... kind of a poor man's cloth.

Ugh, looks like I might have to go into nCloth. Yuk. I like Maya about as much as I like a pick axe in the ear.

Edited May 15, 2011 by pgrochola

[old school]

Along side Ncloth, give the Wire solver a go to simulate simplistic like cloth behaviour. You can take any polygon grid and convert it to a wire object. Pin the corners or use the pintoconstraint point attribute to fix points to animation.

Note that you should adjust the wire width and density. Those two work together to determine the mass of the wires.

Wire objects like to collide against other wire objects although they do work with RBD objects as well...

[symek]

SYmek - less than a few dozen pieces? Really? How often are you doing those kinds of simulations now days?!

This has nothing to do with today or tomorrow, but with a kind of job to be done. I tried to clearly distinguish two kind of RBD simulations: those which comprise a massive amount of objects that need to interact but can be hardly captured by an eye as separate entities, and those with a precise pieces of a matter, which are clearly seen, noticed and tracked by an audience. Rigid body dynamic is *not* limited to destruction shots. So, yes, even today quite often we have to simulate moderate number of objects, but then we need a precision that I have not seen from Bullet engine.

I think it's a crying shame that SESI don't support bullet in Houdini.

I agree, I also would love to see Bullet in Dops as a additional solver.

It's becoming the standard for a lot of the big studios, and for good reason! I'm using bullet in sops to get through a sim with 30,000 convex objects PLUS 120,000 implicit spheres.

Yes, for a reason of being highly optimized real-time engine suitable for doing massive dirty simulations of convex objects. And just that. I hardly believe it is used for a demanding close up shots. Not to mention, they build-in Bullet quite often right into Houdini.

Can DOPS get through >1,000 objects?

They can. Either with ODE solver or by providing precomputed and limited number of collision volumes. In other words, if you ask DOPs to do more or less the same thing what Bullet does, they can handle it. I can easily simulate 10.000 objects on my laptop writing this post, once I understand what am I asking for.

Is DOPs getting a bit outdated?

Quite opposite. As to my knowledge, non of commercially available dynamic engines get even close to DOPs possibilities in terms of flexibility, customizations and robustness. Go ahead, name one!

a bit slow

Quite a bit.

and overly complicated?

True. This is SESI's trademark after all. Advance == not easy.

Now cinema 4D has it.

Please SESI make bullet in SOPs a standard!

You can always assume, that such tools will have anything that becomes virtually standard, and hardly ever anything beyond it.

skk.

[Stalkerx777]

Fully agree with SYmek.

[Macha]

I'm getting to really love the DOP context recently. I think there's a lot of optimizing you can do when you start to understand how it works and with a bit of work and thinking you can do quite complex things. An easy way to start optimizing is to change the data sharing parameter on your forces. By default they don't share but in many cases this is not necessary (but safe. I suppose that's why it is the default)

[Netvudu]

By default they don´t share data? you probably mean by the default they do share, right? (I understood you, but just wanted to clarify in case somebody else didn´t)

[jim c]

(note: I've only done a little tinkering with cloth in both Maya and Houdini)

One thing I noticed was that if you triangulate (Triangulate2D SOP I think is what I used) the cloth mesh that seems to both speed things up and make the deformations a little more interesting.