Match moving

The original footage of the woman on a green screen. 

After opening the layer; we started by using the Roto Brush to key out the woman so that she is not removed. Then click freeze so that she is keyed out for all 179 frames. Then inverted the footage using the alpha channel instead of RGB. Now make a 3D camera and Analyse. There are now tracking points all over the footage. We skipping ahead to 5 seconds so that there were plenty of tracking points on the floor. Then we selected 3 points that created a target that looked like it was on the floor. Then right click and create null and camera. Then made a black solid, made it 3D by selecting the 3D layer cube icon. Then holding cmd and shift, then linked it to the Null layer. Then scaled it up so that it covered the floor. And generated a grid so that the solid was now a white grid. Then moved the woman to the foreground so that she wasn't behind the grid. Then we can get rid of the green background using Keylight (1.2). Using the pipet we selected the green colour from the background and the background was now black. We also had to remove the the invert effect so that the woman would re-appear. Now we add the gravel. Add the layer, make it 3D, parent it with the Null and scale it up. Now the gravel stays beneath the woman and a floor has been added. This could be made smoother so that the edges were not so sharp, but here is the final clip.