UV texturing pre Blender 1.5,

Make two meshes with the same number of vertices..
Take one and name the mesh (ME:) John.. and the second
one, just for fun, name Jane (ME:Jane).

Then in "Jane" its "TexMesh:" option in edit buttons
the name "John". Now map the same image to both meshes..

Put a camera on Jane..

Modify the vertices in in "John" (really screw them up, and use the magnet tool while you are at it).. The texture vertices in
Jane will be affected by the 3D mesh in John with respect to
its texture space. So if you make john into a rectangle
and jane is a square, this doesn't change anything
as when john is a square.

So if you take john and twist him around (assuming a quad),
jane's texture coordinates will also be twisted..

Believe it or not I've actually used this interface for mapping texture
coordinates onto objects pre- Blender 1.5 and it works..
Its less intuitive than using blender UV interface, but its more
hackable..

And you can create animated your source mesh and have the UV textures
modified in your original.. So say you want to do a vortex animation
in blender, you could put video on your first mesh and do animation
on the second without messing with the first. Or animate both at the
same time.. Just remember to add 4 vertices to each so you can adjust the bounding box, which determines the texture mapping..

You don't need to use the UV mapping feature, so if you want to make a tutorial for newbies you don't have to tell them a thing about material buttons.. If you don't want to.. This will also work with procedural textures.. And again you can use this to do 2D and 3D morphs..

I dare someone to write a tutorial using a 3D/2D morph..


Here is an example of a movie I created using it with Relative vertex keying.. I animated that texture mesh source and rendered the affected
mesh..

http://www.bl3nder.com/TexMeshExample.avi

Enjoy..

Another good use for this feature is texturing a snake.
Use a skin tubemapping on a tube and edit a (same vertex count) tube into a snake, et viola, auto-mapped snake.
- Joeri