 For the scene where Professor Carr (Yancey Arias) walked off a  sidewalk that magically became a skyscraper, a set piece was  constructed to look like a sidewalk, so that his foot could seem to  walk right off the pavement and into the abyss. Our shots looking  down were captured from a real skyscraper, while the angles showing  Carr hanging from below were accomplished by building a set piece  that matched the face of the building. For Carrs fall itself,  Yancey was hung on a device called a "hip pick" in front of a "green  screen," which created the illusion that he was falling away from  camera. Mat Beck and his visual