Re: [R] distance to eye in persp()

From: Robin Hankin <r.hankin_at_noc.soton.ac.uk>
Date: Tue 20 Sep 2005 - 00:15:07 EST

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

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Received on Wed Sep 21 02:38:46 2005

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