Apart from the existing answers, I like how 3D textures can be created procedurally as well (actually it makes more sense than a 2D procedural texture), like noise and fractals which will provide good and non-deformed texture details to any angle surfaces without having to select a projection model (UV, planar, cylindrical, spherical and so on).
Instead of sampling a bitmap layer in 3D space, you get a distinct value for each point in 3D space with a basic algorithm - which basically gives you infinite texture resolution and no problems with stretched textures on angled polygons. This is 3D "textures" or rather surface shading to me ^^
I'm actually pretty tired of all the bitmap texture snuff in game development, when I want to dirty down a space ship, I want to apply a few layers of noise formulas and not have to paint a limited resolution bitmap. An old 3D buff can dream, can't he ;)
Right now, pre-baking these sweet oldschool 3D movie surface solutions into color, normal and specular UV bitmaps are about the only fun I get and it feels annoyingly limited. The demo scene (as always) tend to (pre)generate textures procedurally for real-time 3D but it feels hard to find good tools to support this workflow from design to run-time. Most game dev procedural approaches seems to be about mesh generation. Wonder how much the shader pipeline with the help of a depth map/deferred rendering could handle of oldschool 3D noise algos?
...rather than trying to figure out how to map a texture image
parametrically onto the surface of your shape, the volumetric nature
of noise-based textures allows you simply to evaluate them at the (x,
y, z) locations in your pixel shader. In this way, you are effectively
carving your texture out of a solid material, which is often much more
straightforward than trying to work out a reasonable undistorted
These sorts of volumetric noise-based procedural textures have long
been mainstays of feature films, where shaders do not require
real-time performance... all special-effects films
today make heavy use of noise-based procedural shaders... is highly dependent on the
extensive use of the noise function within pixel shaders written in
languages such as Pixar's RenderMan. With a good implementation of the
noise function available for real-time use in GPUs, I look forward to
seeing some of the exciting visual ideas from feature films
incorporated into the next generation of interactive entertainment on
the desktop and the console.