ShrinkWrap Modifier

This entry will be covering use of the ShirnkWrap Modifier.  This modifier is most often used for adding clothes to a character, but it can be used whenever a mesh needs to conform to another mesh.

To demonstrate, I'll be using this simple body frame and giving it a shirt.

The first step to creating a shirt to use a ShrinkWrap is to make a rough mesh composition that mimics the general shape of the mesh to be conformed.  In this case, I simply started with a cube, and began extruding [E] and adding ring cuts [Ctrl + r].

You'll notice, that only half the shirt is shown.  Since the character is symmetrical, I'll be using a Mirror Modifier (with clipping) to ensure the shirt is also symmetrical.

An image of the full shirt with mirror enabled, that roughly follows the blue body.

Next we add the ShrinkWrap modifier to the shirt mesh.  Note that the field labeled Target represents the mesh to conform to.  Note also, that it is a single object, so if the body in this example was two meshes (which it was), they would need to be joined [Ctrl + J] first.  Or as an alternative, to keep them independent, a joined duplicate could be made just to create the shirt.

Finally, in the Offset field, this can be adjusted to scale the modified mesh outward (away from the body).

At first glance, the modifier does a somewhat poor job in that much of the blue body protrudes through the shirt, but this is simply because currently, our shirt mesh has so few vertices that the mesh can't conform to all the details of the body.  This works best for convex shapes, and more vertices would be needed to fill holes.

At this stage some manual manipulation is needed to ensure the body doesn't show through the shirt.  You may even find that you need to add more ring-cuts or extrusions to give enough detail to cover the body adequately.

Finally, a Subdivision Surface modifier can be applied to give the shirt a more smooth look.  More massaging of the mesh may be required.

Although there is some tweaking in the process, the ShrinkWrap modifier saves you a lot of time getting the general frame to match the body, than having to do the entire alignment manually.