How to shorten a mesh in blender

Here's my experience: Sometimes a skirt or dress has a body mesh that does not match the actual nude bottom in size. In that situation, click the nude bottom (will put you into Object Mode). Switch to Edit Mode, and click Backfaces. Highlight (only) the parts of the nude bottom that were showing through the mesh from the skirt (like your pic), and delete by Vertices (X). Be careful not to delete anything that is not distorting the mesh. Any extra vertices get deleted, and you'll have holes in your sim. That said, sometimes you'll find something that can't be altered the way you want, without going through a lot of adjustments. For me, that happened with certain shirts.When you Join them, you will no longer see the nude bottom showing through the "skirt body" (body that comes attached to the skirt), because that part is now gone. The nude bottom sometimes has wider hips than the mesh the skirt has. Technically, you could move the vertices of the skirt mesh to fit the nude bottom, but that is tedious, and not guaranteed to look right, even if you do really well on it.Just don't try to adjust the shape of the nude bottom, or you will see nothing at all in the game when you go to find your new clothing. I don't know why, since deleting doesn't have that effect. :-/ Keep in mind that there are more bottoms that don't quite match the nude bottom, so this is a step you'll be repeating for more than one bottom, I promise.I remember having issues with that exact skirt before (I think I've tried them all now). For that skirt, remember to Extrude Region in just a bit, then Extrude Region strait upwards a bit (not too far, or the edge will intersect through the skirt, unless you just want to Extrude in further first), and THEN Extrude Region in, and fill the hole (ALT+M). This is because you will find it a nightmare to get the Unwrapped meshes to align right, and in this case, it does matter, and will look bad otherwise. Extruding in, then up, then the rest of the way in will make it so it's not visually noticeable. It's because of it's shape. If it were round, like most skirts, it wouldn't be noticeable, and the Unwrapped Mesh would be much easier to align right.This is a case of experience for me.If Mister S knows a simpler way to make the cap look right for that skirt, I'd like to hear it. It looked crazy wrong for me, and raising it up made it all better. Makes the Unwrapped cap even harder to get right, but it doesn't seem to matter at all when it's raised up. I just highlight all the vertices on the Unwrapped mesh, and shrink them to nothingness, and put the in the little black circle (cap texture area). Crude and wrong, but who the heck cares, if you can't even see it? ;)And don't forget to Remove Doubles (Mesh->Vertices->Remove Doubles). I do that for shirts, too.If Mister S has a better suggestion, I'd certainly listen to him, but this process has proven successful for me, and is not really any more work...and looks much better when the skirt cap is raised up, and out of sight. Careful, though. Raise it too far, and you may wish your sim was wearing panties. [NOTE] This is not necessary for every skirt. Only if the skirt's body mesh is larger than the nude bottom's body mesh, and shows through the clothes' fabric. (IMO)

Lexy did you click CASPart first?

Another question.. When i try to import the mesh into s4s, it acts like its cropped, but then there is the piece of shirt below it. Help?

Can I see a picture or your .package file? Does the piece of shirt look skintight? That would be a texture issue.

Yeah, here is what happens. And yes, it actually is skin tight like you said..

Ok, I m here since 2 hours and didnt understand a lot about blender lol, my question is: I want to make a different dress with one spaghetti strap ,there is a similar dress already in the game ,do I have to create a new mesh on blender or can I modify the game's one? These tutorials arent helping me :(

I'm not quite sure what you mean... im so sorry