Tinchompm

Hi, I'm trying to make for an assigment a video mapping projection in which the video reacts to what is happening in the webcam, I know that Resolume Arena can be use for such purposes, but I'm trying to find a free software alternative, or atlist one that is least expensive and for it to be watermark free, does anybody have any suggestions? Also if anyone knows of any good tutorials to get started it will be aswell appreciated !!