in need of explanation about shaders

hey !
heres the problem i’d really like to start working on per pixel stuff, but i have NO idea where to start :

in opengl, you got different extention : GL_ARB_fragment_program , NV_vertex_program which seems to be the same (but exclusively for nvidia card), the equivalent for ati card…
add the register combiners from nvidia to it, and i’m lost

are some programmable shaders and others not ?

so that’s it, if anybody could clarify this for me thanks a lot


thx for the link
i’m gonna read this all