focal distance (-vd length) and front clipping plane (-vo)

Dear Greg,

there's probably a reason why the focal length is measured from the front clipping plane and not from eye point ?
Shifting the front clipping (-vo) shifts the focus too (given as -vd vector length), which is not quite what one would expect, or is it just me ?
Example use: To set the focal point at an object behind a glass pane, the latter is first removed in rvu using -vo , then the front clipping in rpict is set back. -> mis-focused image.
(head release as of 19.11.2012)



pab advanced technologies Ltd,