After a bit of playing around with parameters, I reached this result for a transparent isosurface using a mesh:
The code looks like this
using GLMakie, Meshing, GeometryBasics
ξ = -40:.5:40
c = 20
a = 15
torus = [((hypot(X,Y)-c)^2+Z^2-a^2) for X in ξ, Y in ξ, Z in ξ]
##
with_theme(theme_dark()) do
algo = MarchingCubes(iso=100)
vts, fcs = isosurface(torus, algo)
mc = Makie.GeometryBasics.Mesh(vts .|> Makie.Point3, fcs .|> Makie.GeometryBasics.TriangleFace)
f ,ax,pl=mesh(normal_mesh(mc),
color=(:dodgerblue, .7),
diffuse = Vec3f0(0.8),
specular = Vec3f0(1.1),
shininess = 30f0,
backlight = 5f0,
axis = (show_axis = false, ))
f
end