Replication of the rgl point in the lattice

Question

It would be convenient to interactively select a decent point of view using rgl , and then take the same orientation in the lattice 3D plot. For example, given the following graph using an uninformative point of view.

 library(lattice) wireframe(volcano, screen = list(x=0, y=0, z=0)) 

The same can be opened in rgl on

 library(rgl) persp3d(volcano) view3d(0, 0) 

Interactively easy to rotate the plot to an informative look.

Matrix giving current rgl viewpoint can be extracted

 p <- par3d() p$userMatrix 

How can I transform this matrix into the corresponding parameters x , y , z screen to replicate the representation in the lattice?

UPDATE 1

I tried 42 conversions below. The code shows the rgl plot and the corresponding lattice plot per line. If I executed it correctly (see the code below), there will still be a problem.

 # convert rgl viewpoint into lattice # screen orientation rgl_to_lattice_viewpoint <- function() { p <- par3d() rotm <- p$userMatrix B = 360*atan(rotm[1,2]/rotm[2,2])/(2*pi) P = 360*asin(-rotm[3,2])/(2*pi) H = 360*atan(rotm[3,1]/rotm[3,3])/(2*pi) list(x=-B, y=-P, z=-H) } # read and plot PNG image plot_png <- function(f) { img <- readPNG(f) rimg <- as.raster(img) # raster multilayer object plot(NULL, xlim=c(0,1), ylim=c(0,1), xlab = "", ylab = "", asp=1, frame=F, xaxt="n", yaxt="n") rasterImage(rimg, 0, 0, 1, 1) } # create rgl snapshot with random rotation and # corresponding lattice wireframe plot lattice_plus_rgl_plot <- function() { # rgl plot random rotation persp3d(volcano, col = "green3") theta <- sample(-180:180, 1) phi <- sample(-90:90, 1) view3d(theta, phi, fov=40) v <- rgl_to_lattice_viewpoint() f <- tempfile(fileext = ".png") rgl.snapshot(f) rgl.close() # lattice plot f2 <- tempfile(fileext = ".png") png(f2) print(wireframe(volcano, screen = v)) dev.off() # plot both plot_png(f) plot_png(f2) } # CREATE SOME PLOTS library(rgl) library(lattice) library(png) par(mfrow=c(3,2), mar=c(0,0,0,0)) replicate(3, lattice_plus_rgl_plot()) 

Answer 1

I used the answer to this question to convert from a rotation matrix to angles: Converting an Euler to a matrix and a matrix to euler . I agree that I see a slightly different answer here: How to calculate the angle from a relational matrix . (My linear algebra is not good enough to determine which one is correct.)

 p <- par3d() rotm <- p$userMatrix B = 360*atan(rotm[1,2]/rotm[2,2])/(2*pi) P = 360*asin(-rotm[3,2])/(2*pi) H = 360*atan(rotm[3,1]/rotm[3,3])/(2*pi) > print(list(B,P,H)) [[1]] [1] 41.54071 [[2]] [1] 40.28412 [[3]] [1] 41.24902 

At this point, I already rotated the RGL object at about the “viewpoint” that you suggested. From experiments, I found that negative values ​​applied to the call of the frame apparently give the correct results. "Viewer rotation angle" is probably considered negative for "object rotation angles."

  png(); print(wireframe(volcano, screen = list(x=-B, y=-P, z=-H)) ); dev.off() 

There is a rotate.wireframe function in the TeachingDemos package, but it does not work very well while running rgl-graphs at the same time. (No plot was apparent until I closed the rgl device.) It also seemed unusable on a Mac (thick black line on the graph). It uses the X11 / XQuartz tools to control the interaction through the tk / tcl functions, and I could not reproduce the graphs from the displayed angles. Looking at the code, I cannot understand why this should be. But your mileage may change.

Answer 2

This version of your function uses transforms from the orientlib package and makes the rotation matrix an argument:

 rgl_to_lattice_viewpoint <- function(rotm = par3d("userMatrix")) { e <- -orientlib::eulerzyx(orientlib::rotmatrix(rotm[1:3, 1:3]))@x*180/pi list(z = e[1], y = e[2], x = e[3]) } 

Note that the order of z, y, x is essential.

Using it instead of your function, I get this output:

They get the right rotation. I do not know if a coincidence of perspectives is also possible.

Edited to add: rgl version 0.95.1468, available only on R-forge, contains a version of this function and one for the base graphics.