CGTalk > Main > News
Login register
Thread Closed share thread « Previous Thread | Next Thread »
Thread Tools Search this Thread Display Modes
Old 02-08-2013, 06:17 PM   #46
Mike Pauza
I can see you!
Mike Pauza's Avatar
Mike Pauza
Join Date: Feb 2002
Posts: 578
Ever seen cloth jiggle and stretch like a spring?

Originally Posted by ThE_JacO
Sorry, but what system do you know of that uses non linear springs?
Beside the two facts that A) deflection is enormously expensive to compute in a large set of connected nodes B) a good spring is as close to linear as possible, a rubbery look doesn't come from the spring model, but usually from the constraints within the network.

It's also hard to impossible to simulate thickness cheaply in classic SBDS, since you would need a very carefully placed topology for the hull, and an additional set of springs connecting the two sides that would transmit force instead of constrain the network.
Again, what system have you seen that elegantly does that with arbitrary topology? I know/have seen a few that can do something with a tetra pass, and some CAE models, but in DCC?

I think you are blaming the model (spring networks) when it's actually perfectly fine, when instead you should look at whether you have or not all the options to configure it properly (angular and length constraints, proper dampening control and so on).

ThE_JacO, and everyone else:

No disrespect man, but I'm a physicist turned artist, and I think we are probably more kindred spirits than you realize. I coded with non linear springs way back in 92 (on a bridge simulation project at one of our national supercomputer centers) so I know it's not that difficult to do and worth the effort. Here's an old (but great) Siggraph 88 paper that outlines a nice softbody system:
They had spring & damping forces (like we do), but also plasticity & fracture going on as well, and the results were beautiful and well worth a look. I'm a little touchy on the subject because this work is over 30 years old and still kicks our soft body deformation system's backside in many ways IMO.

Yes the rubbery look does mostly come from the spring model...
The root problem is that springs are a great first step, but only first step because real materials simply don't act like perfect springs. FYI, the "perfect springs" many programmer types learned about in school in basic physics classes are really just theoretical fiction used to illustrate a concept. Real springs are remarkably linear, but only over a certain range. Everything in fact resists deformation like perfect springs, but only over a certain and usally quite small range. If you just want to simulate small deformations, then linear is great, but if you need a fair amount of deformation on supposedly non rubber objects, linear springs don't cut it.

Have you ever seen cloth jiggle or stretch like a spring?
Yes LW damping works great to reduce jiggle (by a process called critical damping in the real world), but doesn't touch the problem of all of our soft bodies deforming like cartoon rubber.
Forces are simply not great enough to resist large deformations accurately. Using damping in a heavy handed manner to try to reduce the amount of deformation produces problems of it's own.

Also, linear spring based compression has compression problems...dense meshes can easily get "turned inside out" in areas for example...for example, if a corner of a soft body cube gets moved too far in the direction of the cubes center for example, it can get stuck in that dent-like position.

Yes, auto grid internal simulation geo is maybe too much to ask for, and maybe unrealistic from a certain pov, but this is the solution for how regular artists can get get non cartoon rubber deformations... Gridding has been around a while in FEA/Engineering type application, and wouldn't be all that difficult to at least come out with a very basic implementation.

Adding non linear springs is low hanging fruit however and should be implemented now.
Heck we should have had it a long time ago. Doesn't really matter that other vendors don't have it yet, in fact it's an opportunity. I might be crazy, but not about this anyway.

Old 02-11-2013, 09:00 AM   #47
New Member
BorderLine's Avatar
RODEZ, France
Join Date: Mar 2011
Posts: 18
Good !!

Very good release for architectural vizualisation !
Fast and stable, new modeling tools, instancing update, ...
All for free if you have updated for LW11 (365 for me).
For this year, I stop my 3dsMax autodesk soubsription,
Too heavy, too much memory problem, too many crashes.
Same results with LW11.5 and Kray !
Old 02-11-2013, 09:52 AM   #48
New Member
United Kingdom
Join Date: Feb 2013
Posts: 5
Surprised actually... this looks like a pretty good release from Newtek this time round... might give it a go after all these years!
Old 02-11-2013, 09:52 AM   #49
CGTalk Moderation
Lord of the posts
CGTalk Forum Leader
Join Date: Sep 2003
Posts: 1,066,479
Thread automatically closed

This thread has been automatically closed as it remained inactive for 12 months. If you wish to continue the discussion, please create a new thread in the appropriate forum.
CGTalk Policy/Legalities
Note that as CGTalk Members, you agree to the terms and conditions of using this website.
Thread Closed share thread

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Society of Digital Artists

Powered by vBulletin
Copyright 2000 - 2006,
Jelsoft Enterprises Ltd.
Minimize Ads
Forum Jump

All times are GMT. The time now is 11:52 AM.

Powered by vBulletin
Copyright ©2000 - 2016, Jelsoft Enterprises Ltd.