I have one more problem. The dress in the picture is fine except when the sim sits down and then it has a gaping hole that you can see right through. How can I fix this?

The invisible piece is either missing on the mesh, or it's a separate piece that has the wrong transparency settings in SimPE. My guess would be the first one.

The skirt was originally a longer one that I cut the bottom off, so I'd imagine that i did cut off the 'invisible' piece. Is there a way to fix it (I've never heard of invisible pieces before)?

Also, thank you so much for all the help! I'm trying things with meshes that I've never tried before and I keep running into problems I've never seen before as well. XD

Body meshes are like... well, sort of like a hollow doll. So a dress is basically a cylinder, and it needs to have a bottom. When you cut the bottom off your skirt, you cut off the bottom of the cylinder.

The easiest way to fix it would be to take the original mesh and get that cylinder bottom from it. It'll look like a flat circle with two holes for the legs. You can move it up to the bottom of your new skirt and align all the vertices. But be sure to copy over the bone assignments if they're different. (Like, if the original skirt was below the knees or at the knees, your mesh piece is going to have different bone assignments than if it was above the knees. If the original was already above the knees and you just shortened it a bit, then you shouldn't have a problem.)

The original mesh was full length, but it also had a slit up the side so they had a strange deal where the legs were attached to the slit. It won't transfer over to the new length. Is there a way to make a new one? I also have no idea what bone assignments are. Maybe I need a tutorial. XD

Bone assignments tell the mesh how to bend as it moves with the skeleton. The basic idea is covered in the beginner tutorials here on MTS.

A skirt with a slit is going to be trickier. Yes, you can make a new bottom piece by using any other skirt and just cutting out what you need. It might not have the right number of vertices, but you can fix that by doing that trick you used for the arms.

Thank you again. I think I've almost got it sorted out now.

Ok, final question (I swear XD).

Do the bone assignments below look correct? I'm especially not sure about the ones I've circled in black. They're a part of the bottom piece of the skirt and they go between the legs (the ones in pale pink). I'm not sure what bone assignments they should have.

Well, it's hard to tell from the colours. But, basically, they should be whatever the ones to either side are (the ones at the tops of the knees). But the ones in the middle should be 50% right and 50% left.

The best way to check if bone assignments are right is to import the mesh into the game and have the Sim move around. Walk, sit in a chair, etc.

Alright, ragequit done with lol. Sorry.

On further investigation this skirt is confusing. There are calf bone assignments above the knee. Is there a possible reason for that or should that not be happening? This is also on a part of the skirt that I haven't touched and is also on the original dress I cut the skirt off.

That's odd. No, I don't think there should be any calf bone assignments above the knee. They're usually set to the thigh at that point.

Okay, if I find another skirt of the same length can I copy the bone assignments from that or would they be different? Does the fullness of the skirt affect the bone assignments? How do you copy bone assignments?

The bone assignments should be similar on whatever skirt you use. Usually, the bone assignments on the thigh are pretty simple, anyway (because the thigh is a long bone that doesn't bend... therefore, it doesn't need to animate anywhere other than at either end). The fullness of the skirt does not matter; the bone assignments will still be the same.

There are two ways I know of to copy bone assignments. One is with the Bone Tool. However, if you're on Windows 7, you won't be able to use it. (I can't remember how to use it myself, as I haven't been able to use it for years.) What I do is go into Extended Manual Edit and copy the bone assignments, one at a time, from the vertex of the original mesh to the vertex of the new one. It's fiddly, but if you're just doing the hem of a skirt, you shouldn't have that many vertices to deal with.

Thanks heaps for sticking with me through all the questions! I think I finally have it ready to upload.