Cloth sim questions

I’m trying to learn cloth sim. I’ve made a couple of side skirts, enabled the clothing in the physics tab, pinned the tops of the skirts, enabled self collision, and enabled collision on the main body. I’m using 2.76 and have not changed any other settings.

This is what I’m getting on frame 15.

I have a few questions. One, I assume if I do a lower poly version of the body, and set that for collision, but don’t render it, the collision calculations will go faster is that an acceptable way to speed it up?

My bigger questions are: Why is it bunching up at the top (if I let the simulation go further it will all bunch up at the top eventually)? Also, why is it not hanging against the body but several inches from the body?

My bigger questions are:
My even bigger question is, Are you going to bother to supply a demo blend file for testing ?

One, I assume if I do a lower poly version of the body, and set that for collision, but don’t render it, the collision calculations will go faster is that an acceptable way to speed it up?
When you tried this what was the result ?

question 1 … YES … its a perfectly acceptable way to speed thing up (if it works for you , do it.) I personally would use some basic cylinders to approximate the legs, but once again ,it depends on your needs. if you want high accuracy, you will be processing for longer.

question 2a . It could be the cloth settings, or it could be the collision settings on the object. its hard to tell without a .blend file
question 2b . The collision settings dictate how far from the mesh it will hang, dont make this value too small or it will clip into the mesh, but don’t make it too big or it will hang t far away.

Absolutely. You just had to ask.

It calculated faster, but I wasn’t sure if the inaccuracy would be a problem and because it isn’t working right anyway, I can’t tell if it would be a problem on my own.

Edit: I can’t seem to get the .blend file to appear in my attachments window. What’s the best alternative to get it to you?

In my experience, the bunching usually means the cloth mesh is intersecting with the collision mesh. That throws the simulation completely off. Try making sure the cloth isn’t touching anywhere.

Sometimes the meshes will intersect partway in to the simulation, which will still cause problems, so check for that as well.

Thanks for the help. It turns out it was a combination of these. The cloth was colliding with the body because of the collision settings and that was causing it to bunch up. I have a question about the collision settings now: Is the collision distance measured in Blender Units or something else. I generally set my scenes up for Imperial because that’s what I know, but the collision distance does not seem to be using Imperial units, but if I switch to Blender Units and create an object that is the same size as the distance I set for collision (I set the collision distance to .005 and created a sphere and set the dimensions to .005 on all the axis in the tool panel), it seems smaller than the collision distance.

I don’t know the answer to that, unfortunately. I usually just set it really really low, and raise it a bit if that causes problems.