"Fl" == Fred lunnon <fred.lunnon@gmail.com> writes:
Fl> What would a canonical example of a projective transformation which Fl> is not affine --- a perspectivity, perhaps? If I read that correctly, you ask, in effect, for an example of what can be done with rational B-Splines but not by non-rational (to put the q in a form understandable by (computer) graphics artists. Yes? The classic answer is to transform a model of some object in a manner consistant with what it would look like in real life. A railroad vanishing to the horizon is a typical choice. The opening text of Star Wars also is a common example. In short, in the graphics world, affine refers to transforms which can be done with non-rational polynomial parametric models in R²P or R³P. I don't know whether that matches the orignal meaning of affine, but that *is* what it has come to mean in the graphics world. -JimC -- James Cloos <cloos@jhcloos.com> OpenPGP: 1024D/ED7DAEA6