在R rgl中，如何选择plot3d中刻度线的位置？

Question

In R,

library(rgl)
m <- matrix(rnorm(300),100,3)
par3d(ignoreExtent=F)
plot3d(m,box=T,axes=F,xlab='',ylab='',zlab='')
axes3d(labels=F,tick=F,box=F)
gr <- grid3d('z')
par3d(ignoreExtent=T)
plot3d(cbind(m[,1:2],rgl.attrib(gr[1],'vertices')[1,3]),col='gray',add=T)

still prints the ticks with numbers:

Shouldn't tick=F parameter in axes3d() get rid of the tick marks and the numbers?

I want to add the x and y axes at the bottom of the graph, not at the top. Also, when I add them using axis3d() , the ticks aren't orthogonal anymore, but inclined in 45 degrees relative to their plane, which I think is ugly.

par3d(ignoreExtent=F)
plot3d(m,box=T,axes=F,xlab='',ylab='',zlab='')
box3d()
axis3d('x--',labels=T,tick=T)
axis3d('y+-',labels=T,tick=T)
axis3d('z++',labels=T,tick=T)
gr <- grid3d('z')
par3d(ignoreExtent=T)
plot3d(cbind(m[,1:2],rgl.attrib(gr[1],'vertices')[1,3]),col='gray',add=T)

If I have to go this second way, how to get rid of the front lines of the box? Or is there another way to print the default tick marks (orthogonal) in the desired position?

Answer 1

Axes in rgl are somewhat confusing and not very flexible. First, there are two different kinds: those drawn by axis3d , and those drawn with rgl.bbox . Only the first type pays attention to the tick argument, and your first example used the second type.

You can remove the ticks in the rgl.bbox axes by setting marklen = 0, marklen.rel = FALSE , but this has the unfortunate effect of putting the numbers right on the box. There isn't a separate parameter to control placement of the numbers independent of tickmark length. If you don't want numbers at all, use xlen = 0, ylen = 0, zlen = 0 .

The axis3d axes are also not very flexible. If you want to change their orientation, you'll need to modify that function. The mpos array holds the coordinates of each tick; change it to make the ticks point the way you want.

Regarding the box: it's fixed if you use box3d() to draw it. If you want the rgl.bbox style, you'll have to use that function. You could also use segments3d() and mtext3d() to construct your own axes, but they won't move around like the rgl.bbox axes.