Re: [R] transparent surface in rgl

From: Duncan Murdoch <murdoch_at_stats.uwo.ca>
Date: Thu 06 Oct 2005 - 04:12:05 EST

On 10/5/2005 11:33 AM, Duncan Murdoch wrote:

> On 10/5/2005 11:10 AM, Prof Brian Ripley wrote:

>> 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
>>
>>
> 
> The library we use (GL2PS) apparently supports PDF output, and that's 
> one of the format options for rgl.postscript(), so maybe we already do 
> support that.  I haven't tried it.
> 

I've just checked, and currently transparency isn't supported even with PDF output. I tried updating the version of GL2PS and turning on transparency support, but so far no luck at all.

If anyone wants to follow up on this I think it would be a nice addition, but otherwise, I think the PNG output is the best we can do.

Duncan Murdoch



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