distance to eye in persp()

Duncan

You can probably just do what trans3d does, but keep the
z-coordinate, to get a reasonable measure of depth.  i.e.

depth3d <- function(x,y,z, pmat) {
   tr <- cbind(x, y, z, 1) %*% pmat
   return(tr[,3]/tr[,4])
}

fantastic!  This is exactly what I was looking for.

This is sufficient for doing fog calculations.  For perspective
shrinkage, you'll need to say where the user's eye is in these
coordinates (or just use depths as distances).

I was going to use hsv(h=1, v=1, s=exp(d/d0) )

(some people believe that red light [ie hsv(h=1, ....)] penetrates  
further
through mist than other colours.  I can now test this !-)

The other idea I had was to plot points with less than the  median
depth with big symbols  and the others  with small symbols.
That would seem to be a nice nonparametric way to do it.
Any other ideas?


very best wishes to everyone

Robin

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