After Effects match moving

The task was to make the girl who is standing in a green room, stand on gravel floor by removing the back ground and tacking the cameras pan movement so the gravel looks real. First you use the roto brush tool and draw a continuous line inside of her body like the picture below and then after effects automatically cuts out the women with the purple line shown. 

After I had done this I dragged it the work area so it follows the pan of the camera throughout the whole clip, After this I need to key her out by searching the invert effect and applying it to the girl. Grab the Invert channel and change this from RGB to Alpha.

After this I had to add a 3D camera to the women so that the gravel floor can be tracked to the women as the camera pans around her, adding the camera analysed the area that women is standing throughout the whole clip. Then I selected the area around her feet so that the floor knows what angle to lie. After the area was ready I applied a null object which will act as the floor.

 After I created a new black solid and then added a grid to it. and Parented this to the null object that was made in the previous image so it stays around her feet like the image below. Then expanded it to the size I want the floor. After this I found the effect Keylight 1.2 and the found the option in Keylight called screen colour click the option and then click the green background making it disappear and then click the FX button so the girl reappears.

 After this I imported the gravel like the one below and made it 3D and like the grid I parented it to the Null so it becomes the floor around the girls feet. and the move the girl to the top of the composition so she is on top of everything. and Finally added a light a parented it to the 3D camera so it follows the girl around.

After I had done this I imported the gravel and made it 3D and parented it to the null object like the grid, it then becomes the floor below the women's feet. Then move the women to above all layers so she is on top of the gravel floor. Then to finish it off I added a light the give the floor an even more 3D effect.