[R] Rgl and plotmath symbols (via sprites): a trial

[Duncan Murdoch]

On 09/09/2011 11:10 AM, Marius Hofert wrote:
> Dear all,
>
> Below is some code where I try to get plotmath symbols in an rgl plot. Duncan
> Murdoch kindly suggested to use a "sprite" for this. As you can see, on can get
> it to work, but my knowledge about grid and rgl is too limited to perfectly
> solve the problem.
> 1) As you can see (please rotate the plot a little bit so that (0,0,0) is "in front"),
> the quality of the .png seems poor. Can this be improved?

Generally plotting much larger and shrinking is the way to do this.

> 2) When I print the file to a .pdf, the label is just a black square... I assume
> one then has to print to png again... hmmm... not perfect.

rgl.postscript has a lot of limitations.  This one may be unavoidable.
> 3) Some parts of the z-axis are covered by the label. How can this be fixed?
> The problem seems to be that sprites have a radius. Specifying a rectangle would
> be better here, but I am not sure how this works (or even if it does).
>

I think I don't see this in Windows, which shows the black text for the 
label on a transparent background.  Do you see a solid background?  Or 
is it just the positioning?  The tick marks go out at an angle, whereas 
your sprite seems to be in line with the zy plane.  I would increase the 
x value to something like 1.4 to place it properly.  (Just tried that, 
and I think I see the problem you had:  the new sprite is obscured by 
the old one.
You may need to play with the depth_test or depth_mask material 
properties.  Not sure if those are visible on CRAN; if not, try the 
R-forge version.)

The other thing I'd recommend is that before plotting the sprite, you 
run par3d(ignoreExtent=TRUE) (and then set it back to the original value 
afterwards).  This will stop the label from affecting the bounding box 
of the plot.

Duncan Murdoch


> Cheers,
>
> Marius
>
>
>
>
>
> require(rgl)
> require(grid)
>
> s<- seq(0, 1, length.out=21)
> M<- function(u) apply(u, 1, min)
> u<- s
> v<- s
> z<- outer(u, v, function(u,v) M(cbind(u,v)))
>
> ## create z-axis label
> png("zlabel.png", bg="transparent", width=70, height=70)
> grid.newpage()
> pushViewport(plotViewport(c(1,1,1,1)))
> print(grid.text(expression(W(u[1],u[2])==c),rot=90))
> popViewport()
> dev.off()
>
> ## plot
> persp3d(u, v, z, aspect="iso", front="line", lit=FALSE, axes=FALSE, xlab="",
>          ylab="", zlab="")
> axes3d(edges=c('x--','y--','z+-'))
> sprites3d(1,-0.4,0.65, radius=0.5, lit=FALSE, textype="alpha", texture="zlabel.png")
> rgl.postscript("W.pdf", fmt="pdf") # print to file
>
> # par3d(c("userMatrix", "zoom", "FOV")):
> #
> # $userMatrix
> #            [,1]       [,2]       [,3] [,4]
> # [1,]  0.7262191 -0.6867201 0.03195775    0
> # [2,]  0.2750087  0.3328032 0.90200466    0
> # [3,] -0.6300603 -0.6462642 0.43054202    0
> # [4,]  0.0000000  0.0000000 0.00000000    1
> #
> # $zoom
> # [1] 1
> #
> # $FOV
> # [1] 30
>
>
>
>