I'm making a movie where the hero characters are human, so now I was wandering. Does movies such as Toy Story 3 (Andy), or the kids from How To Train Your Dragon, have a body underneath their cloth (so the cloth IS a cloth, although simulated or animated cloth is another thing)

Or the cloth IS indeed their body (there is nothing underneath), ala game models, except with more polygons and higher resolution texture.

Should the cloth be animated (via bones) or simulated (via cloth physic)?

Or is there no right answer?

If that the case, what technique does professional use on TS3 and How To TY Dragon?

Thanks. I'm stumped.

It's whatever works for the given situation.

In advanced character pipelines, animators will only move the bare minimum for viewport performance. This means that the rigger will strip everything away but the bare minimum to get the Animator the most performance.

In your specific case, if you don't see the skin, why bother. Most tight fitting outfits hug the skin so closely that running a cloth sim will offer nothing. Just model in the wrinkles and give the animator the controls over them. Can be modeled or done as deforms at render time. H11 now supports the display of bump maps so that is one way to go with displacements.

Should you model the skin under the cloths? Sure. Yes. Gives you reference to build the clothes on top of. Should you have a version of the character that captures the base skin? Sure if you will be seeing the skin at some point in time or your script changes and you see parts of your character you didn't anticipate for.

When it comes to simulations, riggers try to give the animators enough controls to tune the simulations to be run after the animation is done (for the day). Sometimes the sims are fast enough to be flip booked or if too slow, run as a simulation in time for dailies the next day.

The cloth simulations do need something to collide against so the character rig will now include those surfaces weighted and deformed (skinned) for the cloth to collide against. Is that the base skin or the clothes? It's whatever is faster. For longer sims, the geometry is baked out. The geometry generally has to be baked for lighting anyway so the sim part of the pipeline takes advantage of this.

There have been a few Siggraph presentations on directing cloth and hair simulations in the past so that is a good place to start. Some articles on awn and other web sites as well. Time to dig.