rgl.Sweave not producing transparency in pdf plots with alpha

Hi Folks,

I'm trying to get rgl.Sweave to produce plots with transparency.
However, it just seems to produce opaque plots when pdf is the output
type.  Perhaps this is a known issue?  I'll just use .png in the
meantime, but wanted to see about this, as I didn't see it in the
documentation (though it's possible I missed it).

Thanks,
Allie




\documentclass{article}
\title {rgl test}
\usepackage{Sweave}
\begin {document}

This is a test of rgl.sweave's alpha capability.

\begin{figure}
% uncomment line below for png output (correct transparency)
%<<echo=FALSE, grdevice=rgl.Sweave, fig=TRUE, width=5, height=5,
resolution=100>>=
<<echo=FALSE, grdevice=rgl.Sweave, fig=TRUE, width=5, height=5,
resolution=100, outputtype=pdf, pdf=TRUE>>=
library(rgl)
data(volcano)
z<- 2 * volcano        # Exaggerate the relief
x<- 10 * (1:nrow(z))   # 10 meter spacing (S to N)
y<- 10 * (1:ncol(z))   # 10 meter spacing (E to W)
zlim<- range(y)
zlen<- zlim[2] - zlim[1] + 1
colorlut<- terrain.colors(zlen) # height color lookup table
col<- colorlut[ z-zlim[1]+1 ] # assign colors to heights for each point
#open3d()
surface3d(x, y, z, color=col, back="lines", alpha=0.75)
@
\end{figure}

\end{document}