I'm trying to create shadows in a 2D game in such a way that I can have an arbitrary number of lights in a scene, all of which can cast shadows. To do this I think I have to generate a mesh for each light that models where the light can come (e.g. where there is no shadow).
In this tutorial: http://youtu.be/4BtjcH-iLR0?t=4m40s (at 4 minutes 40 seconds) Chris Molini does exactly what I want describing it as 'a polygon clipping pass' for each edge that intersects with the light. However I don't understand what kind of polygon clipping he is refering to here. I have tried to mimick his technique on my own but without success. (I get lost in corner cases and radial+distance ordering around the light).
Here's a screenshot from the video. The square is the light's mesh (basically an AABB containing the light's sphere of influence). Which is gradually adjusted for each edge that intersects with the light's mesh.