Technical Comments

Comments from Pixar:

* Don't get caught up in wanting to do something technical. How you do the Ghost spirit depends how you want to do it artistically
* Find something simple (like 2D effects and comping) to do the ghost. Guestau was too complicated.
* Make sure you can read expression in the ghost.
* Make sure it can be lit.
* Selective transparency might be a good idea.
* Blur behind in compositing
* Oasis in the desert with heat-wave effect could add to it. (using environmental elements to tie into characters).
* Design what the ghost looks like before you start doing it in 3D with the model.
* The environment is big and you can see forever. Make sure you use matte paintings.
* If you have 100,000 pieces of grass there is a Siggraph paper on how to do tons of grass.