[R] transparent surface in rgl

[Prof Brian Ripley]

On Wed, 5 Oct 2005, Duncan Murdoch wrote:

> On 10/5/2005 9:31 AM, Prof. Paul R. Fisher wrote:
>> Hi all
>> I am a complete newbie to this list (just subscribed) and a newcomer to
>> R (an S user from olden times). I have been using scatter3d to create a
>> 3d scatter plot with surface. The graphic is created within the rgl
>> package and I have used rgl.postscript to export it so I can generate a
>> publication quality image. My problem is that the plotted surface is no
>> longer transparent in the postscript output ie. the rgl.spheres that are
>> behind the surface disappear in the postscript image. Can't seem to find
>> any info on this anywhere. Am I doing something wrong? Is there an easy fix?
>
> I think Postscript doesn't support transparency (or at least the version
> of Postscript that the rgl.postcript function targets doesn't support
> it).  You may have to export a bitmapped format using the rgl.snapshot()
> function.  If your original window is very large this may give you good
> enough quality.

Common PostScript (level 2) does not support either full or partial 
transparency (and I guess partial transparency is meant here or the 
surface could just not be plotted).  It would be good to have a rgl.pdf 
which did.  These days PDF is the `portable PostScript' and since version 
1.4 has had alpha-channel supoort.

Ref:

http://en.wikipedia.org/wiki/Transparent_pixels#Transparency_in_PostScript


-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595