Spritesheets for 3D textures?

Question

Out of curiousity, do developers use spritesheets for 3D model's textures? Is that even possible to do with 3D textures? I hardly know anything about 3D, im just satiating my curiosity.

Answer 1

Yes, they do. Developers often pack all the textures for a whole model into a single texture rather than using multiple ones for each component of the model. It would be theoretically possible to put all the textures in a game into a single texture.

This is better because it reduces the number of texture bind operations, increasing performance.

They can do this because each point on each triangle of a model has its own texture coordinate. This means that they have total control over the "window" over the texture that each triangle is showing, therefore more than one thing can be on one texture by using texture coordinates to hide it when it is not needed.

EDIT: A bit more detail on texture coordinates:

Texture coordinates are specified per-vertex, with each vertex having its own coordinate. They are specified with components, U and V, both between 0 and 1 inclusive. These correspond to a point on the texture which that vertex is "anchored" to. This means that a triangle does not have to show the whole thing, and the aspect ratio of the triangle does not need to be the same as the aspect ratio of its window into the texture. See here.