About cloth simulation

With poser 5, you , poser users have discovered cloth simulation.

First, you should understand that what is new in poser is not new at all for a lot of 3D modellers, as cloth simulation in included since a long time in MAYA, and exist also as plugins for 3DSMax, Lightwave, Softimage or Cinema4D.

These simulators are the results of all the physical models research, especially particle based methods. If you are interested in this mathematical part, you have a good tutorial written by P S Karthikeyan.

The interest is that, if the poser 5 tips database for the cloth room is poor at the moment, as cloth simulators have very neat features, you will surely (as I have done) find interest to read manuals, tutorials, tips in the others 3D communities.

First, you should have a look to the UCL Virtual Clothing page to get the basis, and especially consult the links page.

I am sorry for the poor part of the manual dedicated to the cloth room. The maya cloth manual part is bigger than the whole poser manual (well, it’s a joke as maya cloth do more than the poser cloth room as it’s also a cloth maker). But you will surely learn from it. This manual is on line here.

As I use 3DSMax for modelling, I know better the existing plugins for it than for others 3D software. The 3D modelling parts that I will write will be for Max, but should be easily translated for others modellers having the same capabilities.

So you could find useful to download the demos of these plugins, even if you don’t use Max, only to get and read the manuals :

Simcloth

Clothreyes

Stitch
About cloth modelling for simulators

The mesh type incidence

I will first try to explain shortly my own story and how and why most of my clothes were made in poser4. We will then discuss how Poser 5 will change my usage.

My first clothes were made using polygonal traditional modeling and I was unsatisfied because :

  • the folds were quite hard to make to seem natural
  • the mapping was really a lot of work (planar mapping with traditional modeling doesn’t give good results for clothes)

I found my first idea when Reyes Infografica offered its plugin clothreyes for free (it’s always free for 3DSMax3).

The manual says “it’s a good idea to use simple, rounded shapes, and then let clothreyes create the cloth like bends and folds”. And also “to make tightly-fitting clothing create an animation where your character mesh starts scaled down, and then expands to its normal size”.

I made some tests with simple meshes (cylinders for sleeves, closed cylinder for torso, cylinder for skirt…) and all this was working quite well, but the folds were always sometimes strange because of the quadrangular areas ; the mapping problem was not solved.

One day, I found the maya cloth tutorial . They explain that to simulate cloth movement, you need special meshes with varying sizes of triangles that are randomly distributed, with no regularity or stress lines. With polygonal objects, you will always get artificial stress lines caused by the regular tesselation.

At the same time, I heared about a free cloth simulator plugin named simcloth .On the download page was a little plugin named cloth mesh to produce planar triangulated meshes to simulate clothes. I found also that Reyes Infografica had something called hexamesh which had similar results.

And digimation released stitch. Much too expensive, but a look verified that the method was the same, : working on planar triangulated meshes. Triangulated to render as well as possible the cloth folds, planar to avoid any mapping work.

See more on this subject here.

A new modelling way

In fact you find two sorts of software in cloth simulation: simulators only like the poser cloth room ( for Max simcloth, clothreyes and reactor) and software including also “garment makers”, able to model a cloth from a planar pattern (Maya cloth and stitch for Max).

So if you have a 3D modeller with a cloth simulator only, here is a way to get what are doing garment makers :

  • using your character as template, draw your patterns ( 2 planar meshes, front and back) with one of these special plugins. Don’t forget to map them planar now.
  • make a movie where your character goes from flat (scale y to 1%) to its normal size.
  • put your planar meshes on each size of your character (they shoud be very near) and weld the vertices which will be the “seams” on borders.
  • let the plugin do the work…..

Click here to have an example.

And if you have a 3D modeller without a cloth simulator, study the possiblities to import and export meshes to use the best of your modeller and the poser cloth room (I will explain more later).

Then my last problem was that I was unable to get long skirts with folds conforming. Making a thin hip part falling to the ground can work with straight skirts or dresses but is unusable when you have folds as they are distorted and don’t look natural at all. So I limited the skirt part to hip and I used morphing. I got better cloth simulation but the poses were limited.

With poser 5 and the cloth room, this is the past. But keep the same ideas and try to forget usual polygonal or nurbs modelling rules to become a 3D tailor. Learn how real cloth patterns are made and try to mix this knowledge with your modelling possibilities. See here how a long skirt can be made with a cloth simulator.

For those who like period clothes, you can find patterns at La couturiere Parisienne to understand how they were made.

About previous clothes

Can we use in the cloth room the poser 4 clothes ? Well, sometimes.

You can uderstand now that the cloth should have a regular and sufficient verticies density. Just look at it as wireframe and imagine it is a real cloth where your faces would be iron plates like some armor coat ; and imagine how it could bend.

So some clothes will not work properly because the verticies density is unsufficient or too irregular. You must understand that for poser 4 modellers the joints parts were very important, but the parts between the joints less, and the best modellers always tried to have a mesh as light as possible. This was perfect for P4 conforming, but don’t work well with the cloth room.

For the same reason, you will not have good results with clothes where static folds are already included during modelling.

A second reason is that the cloth must not intersect with itself, or with the collision mesh (the character).

Some clothes were build as a solid volumes (they have “caps” at the ends) . Again no problem with poser 4 as the “caps” were hidden by the character but they will not work in the cloth room as they intersect with the character.

Some clothes are self-intersected ; it’s often an error of the modeller (you push a vertex too much). You don’t see it in the render and it’s OK with conforming, but the cloth simulator will refuse to work.

Also, most of the conforming clothes are cut in parts to conform. If you don’t want a cloth where all parts will fall to the ground in a different way, you will have to weld the vertices in your modeller to get a “one piece” mesh (have a thought for the poor modeller who spent a lot of time to cut it and have perfect joints).

About the fabric parameters

This is one of the most difficult part of cloth simulators.

After a few trials, you will be disappointed as you discover that your folds are not really as you would like, and begin to play with the dynamic parameters.

Most of the simulators include examples to help you with the most common fabrics, but it seems it’s not the case of the poser cloth room. You will find here examples of Maya Cloth and Stitch libraries. Even if the parameters range is not exactly the same, this can give you a good idea by comparison of the values of each fabric.

To help you again, I adapted some clothreyes examples to the poser room words :

Rough Canvas / Potato Sack:

Canvas has its fibers set far apart, so it doesn’t catch the wind very well : Lower Air Damping

Canvas has a rougher surface than clothing fabrics: High friction

Canvas does not bend as easily as finer fabrics: Higher Fold resistance

Canvas, after bending, does not wobble around for long, it displays stiff behavior: High Shear resistance

Canvas does not stretch easily, and cannot stretch very far: High Stretch resistance

After stretching, a piece of Canvas will pull back quickly: High Stretch Damping

Canvas is quite heavy: High cloth density

Rubber Mat

A rubber mat is much heavier than most fabrics: Very high Mass

It is much harder to crease a rubber mat than it is to crease most fabrics: Much higher Fold resistance

A rubber mat is porous, wind gets through it easily: Much lower Air damping

After bending, a rubber mat will jiggle around for a while: Lower Shear resistance

A rubber mat can stretch somewhat easily, but only over a short distance: Medium Stretch resistance, low Stretch damping

A rubber mat is something people use as a slip-guard, it’s hard to slide something across it: vey high friction

Silk

Silk is a very finely woven fabric, it does not let much wind through. Highest Air damping

Silk is very light. Lowest Cloth density

Silk can stretch very easily, but only over a very short distance: Low Stretch resistance

After stretching, silk pulls back immediately: Very high Stretch damping

Silk slips very easily across other objects. Very low friction

Silk can fold and bend very easily: Much lower Fold resistance

But always remenber that : parameters should always be mentioned as “higher” and “lower” as opposed to giving absolute values, because a cloth simulator behavior largely depends on the cloth object’s size, its vertex count, as well as other factors (see topic about mesh types and triangulation above). Read more about size here.