Chain with nCloth - prevent it from breaking

#1

Hi,

I need to simulate a metal chain doing different things, like being pulled on, being rolled onto the winch and being unrolled from it. I choose to use nCloth instead of simple rigging or hair dynamics because all shots are to be very detailed and individual links of the chain should behave as individual links, as well as parts of the whole chain. They are to shifting a little when friction lets go, and that sort of thing…

I am using one nCloth for the whole chain. I have tryed to have an nCloth for every link, but it gets very heavy to solve and some of my problems are still present.

My problems are:

  • chain breaks easy, I would like it to be quite strong
  • it’s hard to keep individual links from deforming
  • long calculation times

My scene is one tenth of the world scale (1cm = 1 m), in cm.

I hope someone can help me with an advise, or may be Duncan is around to save the day…
Or may be someone knows another way of doing this?

Thanks

#2

try this…
take 1 hero chain link.
make sim geo to represent it…

  • make 1 poly face with probably around 15-20 edges where the edges are in the centrer of the hero link
    ie, an n-sided face with no internal edges
    now duplicate a few times and arrange them to make you chain…
    the faces will intersect, use wireframe view it should look more like a chain (made of wire)

combine them all into 1 mesh.
make cloth
set self collision to “vertex edge”
increase “self collision milti” to thickness of your hero geo

now display the self collisions, there should be no intersections.

hopefully that makes sense, I dont have anything to draw that here…

.j

#3

quick and dirty example along the lines of what John suggested…

#4

Thank you so much, guys!
It works, it is exactly what I needed… Sim is faster, gives better results and much easier to control. Though I still have some difficulty keeping the chain from breaking - it is 200 links long and sometimes breaks under it’s own weight - but it does work! I guess with some tweaking I will get what we need.

Thanks again

#5

enjoy!

Im sure john will pop in with some more advice, hes known ncloth a little longer. :wink:

#6

If it is still breaking, just raise all of the resistance attributes higher, bend resistance, stretch resistance etc. Raise them all to 100 and see if that helps. Even though they max out at 1 on the slider you can stil type a higher number in those fields.

#7

Yes it did help pushing up values of resistance attributes, as well as quality settings. It does what we need.

You guys are fantastic, thanks for shearing your experience.

#8

i’m guessing you had to increase your substeps…

I never use less than
substeps 20
max collisionIttrs 30

on the nucleus node

glad to hear you have it working. :wink:

.j

#9

really? Ive found sometimes less is better, usually around 10/10 or 10/20.
your sims must take a loooong time :wink:

strangely sometimes a sim that is almost working between 6-10 substeps, freaks out when changed to 20 or more…

#10

That is pretty odd. There were some attributes that were not being properly normalized on substeps that were fixed in Maya2009. The net strength of effects within a substep iteration should be less when the substeps are higher, but for a couple of effects increasing the substeps didn’t do this, which effectively increased the strength of the effect. Most notably wind speed in the first nCloth release was affected by substeps( so high substeps caused a howling gale… this was fixed by 2009 ). If you are getting an effect like this, please submit a bug report. Generally substeps should increase stability in most cases.

Duncan

#11

will do some tests, as i dont remember exactly the issues, its been a few months…

seem to recall that something simple as collisions seemed to bounce and blow up…

#12

I 'm trying to make the same thing with chains …
I now kinda made it with a hair curve and it looks nice. but i realy want to know how you do this? im not that in to Ncloth so could some one plz put down some steps how i can make the chain with N cloth?
( i tested the file and it looked realy nice but dont realy know how you did that.)

#13

its easy :wink:
i did kinda what john wrote.

load the scene, and unhide the cloth object, which is simply a flat poly with 6 edges, for each link… duplicated and combined to make one object. same for the actual render links which are wrapped to the cloth.

its pretty straightforward… just mess around and take a look at everything.

#14

Hi LuxX,
Howard’s sample scene is very well illustrating the principle, and if you will follow John’s instructions you will get there. There is really nothing I can add, except give yourself some time to play with settings to get the result you need :slight_smile:

#15

depends what your idea of a long time is :wink:
and how many layers of cloth you are solving…

you throw a multi layered, 100,000 face costume in there, it aint gonna solve in real-time I’ll tell you that.
But it probably wont solve at all with substeps of 10 :wink:

I have never had an solve issue from too many substeps…

.j

#16

Well guys sorry but as i said i dont know much about Ncloth so help me out a bit plz

take 1 hero chain link: you mean make 1 link that you will duplicate later on ?
make sim geo to represent it= what do you mean by this?
make 1 poly face with probably around 15-20 edges where the edges are in the center of the hero link = I totaly dont understand anything what you say here?
ie, an n-sided face with no internal edges

now duplicate a few times and arrange them to make you chain= I get this part :slight_smile:
the faces will intersect, use wireframe view it should look more like a chain (made of wire)

combine them all into 1 mesh.= know how
make cloth.= know how
set self collision to “vertex edge”.= know how
increase “self collision milti” to thickness of your hero geo

now display the self collisions, there should be no intersections.

hopefully that makes sense, I dont have anything to draw that here…

#17

its pretty simple, look at this image and refer to my scene, you should be able to figure it out-

pink is the hero link, model it 1st.
then model the green simple poly, that fits in the center of the hero.
then duplicate them, combine them, and follow the rest of my scene...
#18

you need to understand that you do not generally (never if you are me) simulate the hero geometry.

you make a version of the hero geometry that is cloth-friendly, simulate that and wrap the hero geo to it

.j

#19

Hi,

thats really a nice method, I tried that and it works but which attribute prevents the geometry from deformation. I tried different Shapes of the sim-geometry and different number of edges and I played around with the restistance attributes. How can I make the chain-elements stiff without making the whole chain stiff?

thanks

#20

stretch,compress,bend and shear resistance.

could play with very little deform or rigidity, but youll get some strange results (may be good for you though)

damp and stretch damp too.

could also play with constraints to keep them stiff… but that will get slow sims.