How to rotate mesh using observables in Makie?

Specific Domains Visualization
1

My aim is to rotate/translate a few objects (STL) in 3D visualizing a running simulation. And Makie seems to be the way to do it. I started simple with just trying to rotate a cube using an observable updated every 100 ms. However, without success.

The code below runs, a cube is displayed, the observable and the meshplot.transformation is updating but no rotation is visible.

How is this supposed to be done?

using GLMakie
#using Makie
using GeometryBasics
#using StaticArrays
GLMakie.activate!() 
fig = Figure()
ax = Axis3(fig[1, 1]; aspect = :data)
cube = HyperRectangle(Vec3f(-1, -1, -1), Vec3f(2, 2, 2))
meshplot = mesh!(ax, cube, color = :lightblue, transparency = false)
linesegments!(ax, [Point3f(0,0,0), Point3f(2,0,0)], color=:red)   # x-axis
linesegments!(ax, [Point3f(0,0,0), Point3f(0,2,0)], color=:green) # y-axis
linesegments!(ax, [Point3f(0,0,0), Point3f(0,0,2)], color=:blue)  # z-axis
angle = Observable(0.0)
on(angle) do θ
    mat = Makie.rotationmatrix_y(Float32(θ))
    meshplot.transformation = Transformation(mat)
    @show meshplot.transformation
end
@async while isopen(fig.scene)
    angle[] += 0.03f0
    println(angle[])
    sleep(1/20)
end
fig
2

I think transformation is only used at plot creation, and afterwards you cannot update it directly anymore.

Transformations | Makie says:

The transformation attribute controls how the Transformation object is initialized. It is processed once during plot construction and then removed.

You can call rotate! with an optional Accum argument to accumulate incremental rotations, it’s described at the top of the linked page

3

Yeah, for this particular case you should probably call rotate!(Accum, plot, rotation...) and translate!(Accum, plot, translation...) to mutate the model matrices.

If you have some more complex transformation you can always update plot.transformation.model[]. That will let you do shear etc.