hi.  this is probably a very simple question with an obvious answer. how do you build circular cloth that will simulate well?  as the radius expands, i realize i need more radial subdivisions or i get a poly heavy circle with needless detail on the inner loops and not enough on the outer loops.  i'm very sure there's an obvious answer that isn't split every face by hand as you expand.  and should one worry about triangles vs. quads?  i'm just not sure at all how to go about this sort of thing. my goal is to be able to create something that drapes and wrinkles well. 

 Try starting with a square plane and adding subdivision levels to it. 

unfortunately, no.  that gets me a square grid.  i specifically want a circle.  for that matter, i'd like to be able to deal with a circular mesh better, like a skirt or the train of a dress.

There are some links to very good cloth sim information such as the Maya Cloth manual, on this page. Copy and paste link into browser as I haven't gotten the hang of direct links  here yet.

http://www.poserfashion.net/About%20cloth%20simulation.htm

The information is not Blender specific but the concepts are transferable to Blender and will give you a good basis for improved cloth simulation.

A couple of the links on the page are to white papers so aren't necessary to read unless you want to know more about the mathematics behind cloth simulation.

I get good results with  this method in situations like you described:

Add a circle, scaling to the circumference of the waistband
ALT+RMB>E>ENTER>ENTER>S  to scale out in a planar direction for creation of the outer circle (the hem edge) Do not move the mouse during the extrusion part of the preceding sequence. Ideally select the circle then take your hand off the mouse until you reach the scaling step.

Select one of the radial edges then CTRL E>loopcut  using the middle mouse button to increase the number of loopcuts to the desired amount. Just try to make a reasonably evenly divided layout at this point. Arrange for any longer or shorter areas or splits on the finished garment. (angled skirt, split skirt, etc.)

(Here's where you get to use the irregularity of poly reduction to good effect for a change.)

First subdivide the mesh to the highest level your computer can handle.

Use either the decimate modifier or the poly reduction script to bring the poly count back down to a reasonable level. This randomizes the poly layout within the boundaries which for the purpose of a cloth sim is a GOOD thing.

Convert quads to triangles and UV map using project from view for an undistorted circular map.

Run the cloth simulation.

Alternatively you can create the skirt using the above method on two mapped planes (rather than an extruded circle) that are UV mapped then joined before running the cloth sim. This allows for better texture creation of patterned fabrics.

thanks for the suggestions!  sorry to take so long to reply- i'm still healing from an operation a few weeks ago, and i'm off and on in terms of my computer time.  i haven't been able to try any of them yet, but i'll let you know if i can get good results!  just to let say, like Serge Marck, i'll be using Poser's cloth sim, not Blender's.  i don't know how to use Blender's yet.   if i can figure it out, i might work with that instead.

A square plane with added subdivision levels does not get you to a square grid? It will give you a perfect circle. Its the easiest way dude.

Im sure lisarichie's way would work too but wow seems really complicated?

Also never use tris in cloth it will make your lighting look like crap because the quads will bend in the middle. Doh! Unless polycount is of no matter to you then hey go for it. Everyone loves a 2 million poly skirt :)

> Quote - A square plane with added subdivision levels does not get you to a square grid? It will give you a perfect circle. Its the easiest way dude. > > Im sure lisarichie's way would work too but wow seems really complicated? > > Also never use tris in cloth it will make your lighting look like crap because the quads will bend in the middle. Doh! Unless polycount is of no matter to you then hey go for it. Everyone loves a 2 million poly skirt :)

for one thing, i'm not a dude.  for another, i tried that subdividing.  immediately on getting advice.  produced a square grid.  attached is the result of repeating this experiment.

just now trying the subsurface modifier, i get something approximating a circle.  even at so many subdivisions i can't see polys, i can easily see how it's really a very rounded rectangle.  frankly i could see that without a circle for comparison, but with one, it becomes really obvious.  it might suffice for a cloth sim, so much thanks for pointing in the general if inaccurate direction.  sorry, but if i knew enough to guess when people said subdivision when they meant subsurface, i wouldn't have to ask these questions.

it does make me wonder how to handle circles in more rigid situations where i'd want a true circle, and if it could be a problem somehow.  it also makes my life more complex because i was hoping for a solution fit for clothing, too.  clothing would be much easier to make with a tube that expands out than a circle that deforms inward.  but i'm looking at meshes i have and trying to see how others' topology works. 

i wasn't planning on something for anyone else but me, so it's kind of moot.  for the picture i was working on, i found that just subsurf modifying what i had worked well.  i wish Poser had that built in.

i've read several people say tris are much better for cloth sims, and some people saying it doesn't matter.  i'm not surprised to see someone say they're worse, but it doesn't really clear things up for me.  more bending seems like an advantage, not a disadvantage.  could you post some images showing the problems tris produce in cloth sims?

just to say, i really do appreciate the help.  and i didn't know there was such a difference between subdividing and subsurfacing before.  so sorry for sounding snippy.

I don't understand... if you want a circle..  why don't you just make a straight line of verts / edges of how ever big you want it, and then 'Spin' it around one end.   You'll end up with concentric circles and lines that extend out straight from the center.  Both of which you could further loop cut in either direction. 

Basically, you'd end up with a mesh that looked just like a spider web. 

Sorry.. don't have time to post a sample picture. 

oh, i totally understand about your time.  here's the problem:  i had two basic needs.  one was a circular blanket/cover.  i ended up using a rectangle, which worked better.  the other was a dress for V4 that made a big circle on the ground.  this i brought into Poser, ran a cloth sim, had pretty horrible triangular bends in the bottom/train that should have been wrinkles, brought it back into Blender and subsurfaced and smoothed it into a nicer shape, then reimported it as a static prop.  in both cases, the problem was that by the time the very large outer edge had enough detail to simulate properly, the inner part had so many unnecessary polys that it was too heavy to use as cloth.  i needed a circle with a more even distribution of polygons. 

your solution would be great if i needed a rigid circle, or a very small one.  it's not so great if what i need is something with a significant radius to deform in soft, believable folds and wrinkles.

Quote - A square plane with added subdivision levels does not get you to a square grid? It will give you a perfect circle. Its the easiest way dude.

Im sure lisarichie's way would work too but wow seems really complicated?

Also never use tris in cloth it will make your lighting look like crap because the quads will bend in the middle. Doh! Unless polycount is of no matter to you then hey go for it. Everyone loves a 2 million poly skirt :)

Shrug......quads are 2 tris with an implicit shared diagonal and "bend in the middle" on a regular basis in organic modeling.

Oddly enough I've never had an issue with the mesh making my lighting look like crap, have had it the other way round a few times though. :lol:

Straight quads can force folds to form along undesirable lines during a cloth sim. Using a randomized tri mesh helps eliminate this allowing the cloth to deform more freely along the form of the underlying object. It took me a little reading and testing to get this idea too.

Poly counts....knew I should have highlighted the part about reduction.

Cloth sims don't need highpoly counts to work. The subd level and subsequent decimation decribed was to take advantage of the randomization caused by the decimate modifier to break the artificial lines of the quads.

Cloth simulation has been around a day or two so there are various avenues of approach to the idea. Flexibility in this approach can be beneficial to accomodating different situations that arise when modeling, but then to each his own.