R rgl distance between axis ticks and tick labels

Question

I am plotting some point data using plot3d(). I would like to bring my y axis tick labels a little closer to my y axis tick marks.

The best way I can think of doing this is to

1) plot the data first, without drawing the axes

2) call on axis3d() to draw the y axis and tick marks but suppress labels from being drawn.

3) query the current position of each tick mark in 3D space. Store positions in a vector.

4) use mtext3d() to add labels at positions based on an adjustment to the vector

I am having a problem at step 3. I don't know how to query the position of each tick mark. par3d() allows you to query a number of graphical parameters, is there something similar I can use to get the position each y axis tick?

Am I approaching this wrong? Probably.

Here is an example piece of code, without text added for y axis labels....

require(rgl)
x <- rnorm(5)
y <- rnorm(5)
z <- rnorm(5)
open3d()
plot3d(x,y,z,axes=F,xlab="",ylab="",zlab="")
par3d(ignoreExtent=TRUE)
par3d(FOV=0)
par3d(userMatrix=rotationMatrix(0,1,0,0))
axis3d('y',nticks=5,labels = FALSE)
par3d(zoom=1)
par3d(windowRect=c(580,60,1380,900))

Answer 1

One way to do this is to explicitely define the tick locations before drawing the axis, instead of querying them after drawing the axis. Then you can use the line=option of mtext3d to control the distance of the tick labels from the axis like this:

require(rgl)
rgl.close()
x <- rnorm(5)
y <- rnorm(5)
z <- rnorm(5)
open3d()
plot3d(x,y,z,axes=F,xlab="",ylab="",zlab="")
par3d(ignoreExtent=TRUE)
par3d(FOV=0)
par3d(userMatrix=rotationMatrix(0,1,0,0))
par3d(zoom=1)
par3d(windowRect=c(580,60,1380,900))

# and here is the trick:
my.ticks <- pretty(y, n=5)
axis3d('y', at=my.ticks, labels=rep("", 5))
mtext3d(paste(my.ticks), at=my.ticks, edge='y', line=.6)