I was just wondering if edge detection could render something nice for Alien Blitz, and now that I understand better how the multi pass work I can easily add an edge detection pass.

(screenshots are: soft edge, stronger edge, no edge; only terrain edge is displayed atm)

(I also need to correct shadows, this shader is a bit old, I should use the one from the tutorial)

Basically this new pass renders the scene saving only normals (rgb) and depth (alpha) information, then in the final render I check if there is a significant difference in these informations.