Step 1: Start by grabbing frames from a video source. These will be the background that you will composite your CGI onto. (A Matrox Rainbow-Runner is an ideal solution for semi-professional video grabbing.) Step 2: Next perform match-move with the CGI camera. It is important to take into account the lens size, focal distance, f-stop and zoom of the real camera. Next place your models and light them correctly. Step 3: Render your frames both with a colour channel... Step 4: And an alpha channel which takes account of shadow density. Step 5: Finally composite the original backdrop and the new frame... Step 6: And you are left with a perfect matte. Disclaimer: No profit was made through the production of these images, all trademarks belong to their respective owners. Star-Tac is a trademark of Motorola Tel Co. Dates: January 98 Details: These images show the steps required to composite a CGI character onto existing footage