Shadow of feet dont line up

First I have a greenscreen actor walking towards the camera. I made a floor in 3d out of a plane turned 90 degrees. Green screen media is also 3d. Now i add a light and move it so there is a shadow behind the actor on the floor. So far so good. I line up the floor so the shadow starts at the actors feet. But when the actor walks towards the camera the feet go "under" the floor and is "burried" This is because the medialayer has to be moved down to get the shadow to line up.

How do I solve this problem ? If i move the actorlayer up the shadow will float.
Any ideas?

Thanks

Marty

Can you upload a video showing this, as it'll be easier to offer advice if we can see it in action.

Ok here is the clip.




The feet dissapear when the actor walks toward the camera.

Looks like your actress walks towards the camera in the video clip, which means she moves lower in the frame. Because you've initially lined up the shot with her earlier position, the video layer is intersecting with the floor plane. Then, as she walks closer to the real camera, and moves lower in the frame, she moves onto an area of that layer that is below the floor.

It's important to remember that while the video layer itself is in 3D space, it's still a flat plane. The girl isn't actually coming towards the virtual, 3D camera. She's just a video projected onto the flat layer.

To ensure that she's always composited on top of the floor plane, even if she's physically below it in 3D space, create a new Grade layer and place it between the girl layer and the floor layer. This will separate them into 2 distinct 3D spaces, so that the girl is always 'above' the floor regardless of where they both are in 3D space.

Does the video layer actually need to be in 3D? It looks like it would work just as well if you kept it in 2D, as there's no camera move.

Hope this helps!

Super. It worked! At first the floor layer turned white and the shadow disappeared!!! But then I moved my 3d lights under the grade layer as well and BINGO.

The only thing is that the shadow stays behind when the actor moves forward. So I have to animate the floor down for it to keep up. Dont know if there is a better way to solve this?

I do need the scene to be 3d, as I have cameramoves as well as other actors in the 3d scene. Its like filming in a real studio with real lights and cardboard actors in front of a moving camera. Opens up the door to virtual sets I think.

Thanks a lot.