CG Element Integration
Visible seams between CG and live action elements cause the most difficulty, due to the difficulty of achieving a subpixel match in real time. It is recommended to hide the seams between CG and live action whenever possible, so that small amounts of sliding are not noticed. Ways to achieve this include:
- Feathering the practical surface (sand, etc.) to a green floor
- Having a raised live action edge, so that the intersection to the CG is hidden
What practical objects will be present in the scene? Tables, chairs, and midground objects are very helpful for selling the shot.
Our first recommendation here would be to make the floor practical using real tiles. This will limit the amount of floor contact between your actors and CG elements.
Greenscreen floors cause a very large amount of green spill to be reflected onto the actors, and make it very difficult to key correctly without many artifacts.
Photographs of the stage are very useful for planning.
For 3D CG elements to connect to live action elements, the CG elements must be modeled precisely, with 1 CG unit = 1 centimeter. Previzion’s model units are all centimeters.
In addition, the live action coordinate system origin must match the CG coordinate system origin. (0,0,0) must be located in the same place for both CG and live action for an accurate match.