[R] distance to eye in persp()

[Robin Hankin]

Hi

the manpage for persp() has a wonderful section where a the trans3d 
()  function
is used with points() and lines() to add red dots and a green sinusoid
to the Mexican hat surface.

Does anyone have a way to tell what distance  a point is from the eye/ 
camera?

Take the following line:

lines (trans3d(x, y=10, z= 6 + sin(x), pm = res), col = 3)

Is there a function like trans3d() that returns a vector of distances  
from
the x,y,z point to the camera?  I want this so I can plot clouds of  
points
with the further ones in smaller plotsizes, and perhaps even fading  
to white
(as though viewed through fog).





--
Robin Hankin
Uncertainty Analyst
National Oceanography Centre, Southampton
European Way, Southampton SO14 3ZH, UK
  tel  023-8059-7743