Find the 'depth' of a point relative to a camera. This is the signed distance of the point from a plane with:

• origin point equal to the camera's eye point
• normal direction equal to the camera's viewing direction

The returned depth is positive for points in front of the camera and negative for points behind.

Project a point from 3D world to 2D screen coordinates, by supplying a rectangle that defines the shape and size of the screen. Points directly ahead of the camera will end up in the center of the given screen rectangle.

Note that the projected 2D point may be outside the given rectangle, if the given 3D point is outside the field of view of the given camera.