Thanks for the answer.
Now I have all my polygons directed to the same side, and the most of the polygons show correctly. But I continue with a problem. Some of the polygons appear black, they doesn´t apply the color that I have put to gl. I have made some tests and it seems to be related with concave and convex polygons, because when I delete some point it works. I delete the points which go toward the inside of the polygon.
I´m going to try to show an example of two polygons (with extrude) that execute the same code, the only difference is one point. Do you have some idea how to solve it??