Anyone know GLSL? (silhouettes)

OK, I don’t know GLSL at all.
I want to make a silhouette shader.

I have two ideas for implementing it.

1st: add black wherever a back facing face meets a forward facing face.
2nd: add black where normal is > 90ish degrees from camera angle

so, if someone could either show me a code example, point me to a good place to learn GLSL, or both, I would really appreciate it.


I am no programmer, but I think both methods would probably result in some unpredicable errors and thus look quite bad.

Back in quake3 days there was a very robust work around that basicly went like this: Render the character twice, with one slightly larger, an all black texture and always in the background of the real character. This way you really can not get any unwanted errors, and I am guessing something similar could be done with shaders also, right?

ok… by silhouettes i don’t mean the outline of a character, i mean pencil sketch style, to use with a cel shader.

you CAN do this by duplicating a mesh, Alt-s scaling it up a bit, make it black and reversing the normals, but i wanted a shader solution.

I think someone did something like this before, but it didn’t turn out so good. i wanted to learn how to do it with one of the two methods i described above.

EDIT: could someone just post a link to an easy to understand GLSL tutorial?