Hi ,
After seeing keepee's example , I wanted to make my own implementation of the shadowcasting , so after 2 hours of procrastination , Here it is !
Mine doesn't have artifacts and is not CPU intensive ...
Edit : It even has a steady 60 FPS , supports multiple lightsources and complex polygons :)
The only flaw it has is you need to set up the mask by yourself , but that shouldn't be that hard ...