Because my alien character was created in Maya I also created an environment for it to exist in, this would be my virtual set extension where I would place my green screen footage of Jeff into it in post. As you can see the environment itself is very simple, however once rendered out it looks a lot better and if there was too many objects within the scene it would have felt too cluttered as I wanted to create a clean cut look. As I have mentioned in a previous post, the background would just be a texture dropped behind the footage in After Effects. The image below shows a plane for the background but this is just for the lights to bounce off of and produce reflections.
When going into post with a virtual set and character you have to make sure both the models and the real footage work together as a whole. They both have to look like they have come from the same thing for it to be believable. In order to achieve this as best as possible some colour grading needs to be applied, tint is a good one to use as you take the blacks and whites from the scene and can adjust your footage to it accordingly. I did this to all my shots and I also turned down the lightness of my alien character as I found that it was a bit too bright when put in the shot with Jeff.
I also had to do some other adjustments, especially with the ambient occlusion layer as this tends to leave a harsh outline around the objects. To get rid of this and to create more of a seamless integration, I used a simple matte choker to take away that harsh edge by a few pixels. By doing this it already makes the character sit far better within the scene. With virtual set extensions you also have to make sure the lighting matches how you set up the lights when filming green screen. Ideally you would set up the lights when filming to match your virtual scene, by doing this it makes life a lot easier. Trying to put in a light in post would be a lot harder than doing it all correctly in the beginning.