The problem with Cloth

[Ascalon]

I am trying to properly handle cloth clothing on characters. My goal is to get proper wrinkles, gathers, bunches, and other such defining items of cloth. Cloth simulation is sufficient for handling motions by the characters, but it is not enough. I will explain the issue I am having, and I am hoping that someone can either tell me a solution or workaround, or confirm that there is no current solution or workaround.

The problem: How do I keep my clothing meshes consistent, and yet still get them into the position I need them in before cloth sim runs?

Blender (and other 3D programs in general) handles every type of mesh the same way, and essentially like clay. This causes problems for cloth. To get an idea of why this is an issue, consider the following:

You have a large piece of flat cloth set out, unwrinkled, on a flat surface. If you pull one corner, gently, the entire cloth is pulled slightly in that direction. A few wrinkles will be created. The cloth changes layout, but does not change shape. However, if you make a flat plane in Blender and then select a corner vertex and move it, then just that vertex moves. Even if you select several or use proportional edit, the rest of the cloth never responds. You change the base size of it.

The same is true with a pair of pants. Consider some baggy jeans or cargo pants. They have a certain starting size. If you flattened them out (unwrapped them) it would look like a clothing pattern. You want to get them tucked into some boots. How do you do this? If you grab the bottom loops and scale or translate the vertices to get them inside the boot, you haven’t actually tucked the pants in, you have just re-designed them. They are now tapered at the bottom. Real fabric has to be scrunched and folded over itself to fit into a boot. This folding and scrunching creates wrinkles all the way up the leg. If you just scale it down, you don’t get these wrinkles, and your clothing looks like a rubber tube.

The issue comes down to this: In blender, if you move a vertex, it does not keep consistent size of faces and edges. Real cloth pulls the rest of it along with whatever segment you are moving. If there was some way to force edges to stay the same length between points, then we could have this effect. (Of course, in reality, cloth does have some stretchiness, but not all types have much, and it is an entirely separate issue.)

So, I am trying to figure out what tools I can use to manipulate my cloth items without distoring their base shape (note that Cloth sim does not distort it, so it is behaving properly). I need to be able to bunch and wrinkle things up, rather than just translating the vertices (even after moved, if unwrapped, they need to still have their original sizes.) The only thing I’ve found that is similar is the ‘Comb’ tool in particle hair. This allows you to comb hair strands, and they properly pull on eachother.

Has anyone else dealt with this problem? Are there tools, addons, or ways to use cloth sim that I’m missing?

[Orinoco]

Cloth simulation is an animation. In order to get the effect you are looking for, you have to animate the movement of that corner vertex. The simulation is what is keeping the clothing mesh consistent, so you can’t get it into a simulated position before you run the simulation. If you move it in edit mode, you are simply editing the mesh into a new shape, as you have noticed.

So, use hooks. Put your mesh on a collision object, select the vertices in the corner, then Ctrl+H >> Add hook to new object. This will create an empty connected to those selected vertices. Animate the empty, the vertices will move. Second, make those vertices into a vertex group, and, when you add the cloth modifier, pin that vertex group. Now when you run the simulation the pinned vertices will be dragged across the collision object by the animated empty, and the rest of the mesh will display simulated cloth behavior.

The cloth will probably need considerable tweaking to get the simulation to give you the results you want. And adding enough hooks and animating their empties to simulate tucking pants into boot tops would be time consuming and tedious. The work-around to avoid the simulation (or much of it) is to model in the ends of the tucks and pleats. Don’t simply scale in the hem of the pants, make folds in the hem and keep the length of the hem as close to the original as you can. Then make the whole hem into a vertex group, and pin the whole thing, to preserve the beginnings of the creases and folds, and let the cloth simulator handle the folds elsewhere on the cloth.

Hope that this makes some sense.

PS: I really like your Project Maiko

[Ascalon]

Thanks for the response, Orinoco. I had figured I would have to do what you say in your third paragraph, but I hadn’t thought to try using hooks. I’ll do some experimenting!

PS: Glad you like it!

[Orinoco]

There is a sewing add on that is currently broken, but might be available again after 2.7 gets going.

I’ve been doing some experimenting trying to get some nice clothes on my anime girl, but so far have discovered a lot of things that don’t work well. I suspect I’m going to wind up with a really bastardized work flow that is different for each item of clothing.

[Ascalon]

I’ve been waiting to try that addon as well.

I’ve been able to get good results just modeling stuff and eyeballing what looks right, but I want it all to be accurate behind the scenes, so to speak, as that gives the best results for cloth sim. The problem is that most of the good looking stuff out there is just sculpted, and only looks good in the one pose the sculpter made it in. This is no good if you want stuff like accurate wrinkles across multiple poses.

Once I get it all figured out, or at least figure out what our best options are, I’ll write about it.

[Orinoco]

Here is a technique I tried that seems to have promise:

See that ring around her middle? That’s a duplicated and separated ring of my girl’s waist, with belly button removed and scaled up to be outside the dress fabric.

It is a collision object, and it’s animated with a shape key to undo the scaling up. Here it is half way through the simulation.

Now it is back to the basis shape, just slightly larger than the model’s waist (enough room that the cloth isn’t forced to poke through somewhere. I still have to experiment with just how much larger it has to be.)

The bodice portion of her dress is nicely shaped over her chest, and the skirt portion has some nice, natural wrinkles and folds. I still need to experiment in how to remove the helper object from posing or animations, I’m thinking either pinning the vertices underneath it, or giving it an invisible material shader (or putting a buckle on it and calling it a belt).

But I’ll bet this technique would also work well with your tucking-into-boots challenge.

[Ascalon]

I’ve done that with belts on dresses as well, and was planning to try something like that with a boot. I’m not actually doing animation, just poses for still, so removing helper objects isn’t an issue.