textures coordinates generation

can someone explain what is the meaning of
generating texture coordinates ?
till now i just have texture mapped some quads, so the coordinates are written in a file that i load, with the vectrices…

when is it needed to calculate them ?


Well, if you were texture mapping a complex object you would obviously need to generate some complex coords, far more complex than just a quad which you can just do by hand. Therefor you will need an algorithm…

ok ! i’ve got the point,
so, if in your scene you’ve got some complex objects and some non-complex ones, is there a way to have a function that calculate both the complex and the easy objects, so everything is calculated ?
or maybe the non complex objects coords are
still entered by hand ?


for 99% of objects/meshes the texture coordinates will have to be calculated by the person that makes the models (with eg a 3d modelling program) exceptions where gl can calculate the coordinates are for ‘effects’ like reflection mapping etc