i have to render some elements tracked into a film. i would like to have the 3d elements with al clean alpha channel containing the shadows. so i use a shadow matte material on the floor.
when i turn of the scene´s background object i loose the lighting of the background image and end up with much too dark shadows from the floor. when i leave the background turned on i did not find a way to get rid of it in the alpha channel. is there a way i can have the background contributing to the lighting of the scene but not to the alpha channel?
thank you much!