Problems With Ncloth

[chris-wombold]

So I've made huge mess. I'm working on a short animated film. Rock in the Road. Part of my job is the cloth sim. I've never done this before. We are using Maya nCloth, which is suppose to be cake. And it works... kinda. There is more than one problem I'm having here.

I'll start by giving you as much information I can about my workflow.

1. I reference the character (that includes the cloth mesh).
2. I convert nCloth and Passive objects. (I'm using stand in geometry to keep the the hands of the character from clipping with the cloth.)
3. I add constraints.
4. I let the cloth settle for 24 frames, set the Initial State and then relax the Initial state.
5. I slowly position the character to the 1st pose of the animation; save and relax Initial State.
6. Cache and play the simulation.

I have my settings as follows:

Bounce 0
Friction 0.05
Mass 0.2
Lift, Drag, and T-Drag at defaults
Stretch Resistance 150
Compression Resistance 10
Bend Resistance 0.05
Bend Angle Dropoff 0.3
Shear 0
Rigid 0
Deform Resistance 0
Input Mesh Attract 0
Damp 0.2
Stretch Damp 0.2

Quality Settings
self collide 30
trapped check and self trapped check on
Substeps 25
Collision Iterations 40

Here's a link to a video.

NobleMan Cloth Sim

So I guess I'll start with the most obvious problems first.

My first problem is nCloth can't seem to keep up with the character movement. If a character moves too fast then the cloth breaks. I think I can fix it by turning up the quality settings, but I'm not sure.

My second problem (and this is more annoying of the them) is the cloth doesn't flow naturally. It seems very stiff, but at the same time it bends very readily on its edges. Not only that, but once the animation stops the cloth refuses to settle. Well, maybe settles not the right word: the cloth stops when the character stops and refuses to overlap and drape like cloth should.

My 3rd problem is with constraints. I'm am using a Point to Surface Constraint on the waist and the neck of the character. The constraints work like they are suppose to the but the non-constrained cloth near them behaves inconsistently. It likes to ride up and around the constraint like some magical force is pulling it up, and it won't fall back down.

I really hope someone can help me fix at least some of these problems.

[duncanbrinsmead]

In general increasing the substeps may help with collisions on the fast moving parts. Also it can help to make the collide width a little larger.
For self collisions you may wish to use the "vertex" selfcollisions. Set solver display to selfCollision and increase the selfCollideWidthScale until the sphere slightly overlap. This will create a type of bend resistance that may work better for you.

Make sure your spaceScale on the nucleus node is properly set. If you modelled in cm it should be 0.01 (which will in turn make the effect of gravity much stronger). If grid in your images was showing single units then the spaceScale would need to be about 0.3. (too low gravity can make cloth seem stiff)

Also make the strength of the constraints as low as possible. As the body deforms they may pull on the cloth too much, fighting collisions in places like the shoulder.

Make sure the normals on the body all point outward and that the deformed geometry does not have any triangle overlaps.

Duncan