How to draw a texture using indices

I'm drawing a simple cube using 8 vertices and 36 indices. No problem as long as I don't try to texture it.

However I want to texture it. Can I do that with only 8 vertices? It seems like I get some strange texture behaviour. Do I need to set up the cube with 24 vertices开发者_如何学C and 36 indices to be able to texture the cube correctly?

It just doesn't make sence to use vertices AND indices to draw then. I could just as well use vertices only.

One index refers to one set of attributes (vertex, normal, color, edge flag, etc). If you are willing to have the texture mirrored on adjacent faces of the sides of your cube, you could share both texture and vertex coordinates for the sides. However, the top and bottom faces sharing those same coordinates would not work -- one axis of the texture coordinate would not vary. Once you add other attributes (normal in particular) then a cube would need 24 individual indexes (each with vertex, texture and normal) to have "flat" sides.

Another approach that may work for you is texture coordinate generation. However, needing 24 individual vertices for a cube is perfectly normal.