I tried following the example in this tutorial to create a 3D surface plot with a ‘side band’:
using GLMakie; GLMakie.activate!() # v.0.8.2
cmap = Reverse(:Spectral_4)
lightpos1 = Vec3f(4, -5, 5)
set_theme!()
update_theme!(
lightposition = lightpos1,
Axis3 = (protrusions = 0, elevation = pi/4, azimuth = -pi/3),
Surface = (specular = Vec3f(0.2), shading = true, diffuse = Vec3f(0.8)),
Band = (specular = Vec3f(0.2), shading = true, diffuse = Vec3f(0.8)),
)
# generate data for sample plot:
x = range(-3, 3, length=100)
y = range(-2, 2, length=100)
z = [sin(x + y^2) for x in x, y in y]
xpt = [x for x in x, y in y]
ypt = [y for x in x, y in y];
function boundary_values(a)
return [a[1,:]..., a[2:end,end]..., a[end,end-1:-1:1]...,a[end-1:-1:1,1]...]
end
bxpt = boundary_values(xpt)
bypt = boundary_values(ypt)
bzpt = boundary_values(z)
upper = Point3f.(bxpt, bypt, bzpt)
lower = Point3f.(bxpt, bypt, bzpt*0.0 .+ minimum(bzpt))
lower_colors = bzpt*0.0 .+ minimum(bzpt);
###########################################################################################
fig = Figure()
ax = Axis3(fig[1,1]; aspect =(1,1,0.5))
surface!(ax, xpt, ypt, z; colormap=cmap, shading=true)
band!(ax, lower, upper; color = [lower_colors..., bzpt...], colormap=cmap)
fig
The results look like this:
Since I set the lightposition to Vec3f(4, -5, 5), I expect a light source located at (x,y,z)=(4,-5,5) (please correct me if I misinterpret lightposition). From the figure, it does look like the light source comes from somewhere near the specified coordinates based on the color shading, but the color shading at the side bands doesn’t look right. When I rotate the 3D plot in the pop-up window to inspect the color shading, it looks like the apparent light position for the band is rotated by 180 degree in the x-y plane compared to that for the surf:
Is this a bug or are there some tricks in setting the light position?