Blending makes the edges appear


I have a simple (to describe) problem: when i use alpha-blending on two polygons that are sharing an edge (such as additive blending), the edge is processed twice (making it appear twice brigher). Strangely, i didn’t have the problem with an older driver, and my code hasn’t changed a lot. I don’t have the problem with normal polygons (only blended, since i must use the GL_LEQUAL depth test). I’m wondering how to fix the problem… can’t i tell OpenGL not to draw the last right or bottom pixels of a polygon when it’s filled ?