Sets/returns parameters used by (look-encompass).
view-fraction is the portion of the camera window filled by the object,
clip-ratio is the max allowed ratio of near-to-far clipping planes.
The near clipping plane is 1/near-margin times closer than the near
edge of the object, and the far clipping plane is far-margin times
further away. Returns the list of current values.
Defaults: .75 100 0.1 4.0