Drawing concave polygons

I have to draw convex and concave polygons. By clicking the mouse, the user adds a point and the polygon updates itself.
How can I do it?
I appreciate your help.

PS: Polygon in 2D

[This message has been edited by fandecine (edited 10-14-2002).]

Hi !

Take a look at the GLU tesselator, it takes a concave polygon and converts it into triangles, strips, fans or lines for you.