Different behaviour between CairoMakie and GLMakie

Hi all,

I am confused since a couple of days, because GLMakie and CairoMakie have a different behavior. Here is the MWE:

using CairoMakie
# using GLMakie

x = range(0., 2π, 100)
z = sin.(x)

x = range(0., 2π, 100)
z = sin.(x)
zmin = minimum(z)

lower = [Point3f(x[i], 1, zmin) for i in eachindex(x)]
upper = [Point3f(x[i], 1., z[i]) for i in eachindex(x)]
edge_start = [Point3f(x[1], 1., zmin), Point3f(x[1], 1., z[1])]
edge_end = [Point3f(x[end], 1., zmin), Point3f(x[end], 1., z[end])]

fig = Figure()
ax = Axis3(fig[1,1])
band!(ax, lower, upper, color = (:blue, 0.1))
lines!(ax, upper, color = z, colormap = :viridis)
lines!(ax, edge_start, color = [z[1], z[1]], colormap = :viridis)
lines!(ax, edge_end, color = [z[end], z[end]], colormap = :viridis)

fig # for plotting CairoMakie figure in VSCode
# display(fig) # When using GLMakie

While this code works fine with GLMakie, it throws the following error when using CairoMakie: Looking up a non-finite or NaN value in a colormap is undefined.

After inspection, the problem comes from lines!(ax, edge_start, color = [z[1], z[1]], colormap = :viridis) and lines!(ax, edge_end, color = [z[end], z[end]], colormap = :viridis), but I have to admit that I can’t explain why GLMakie and CairoMakie behave differently in this case.

Thanks for your help.

Julia Version 1.8.5
Commit 17cfb8e65ea (2023-01-08 06:45 UTC)
Platform Info:
  OS: Linux (x86_64-linux-gnu)
  CPU: 20 × Intel(R) Xeon(R) W-2255 CPU @ 3.70GHz
  LIBM: libopenlibm
  LLVM: libLLVM-13.0.1 (ORCJIT, cascadelake)
  Threads: 1 on 20 virtual cores
(@v1.8) pkg> st
Status `~/.julia/environments/v1.8/Project.toml`
[13f3f980] CairoMakie v0.7.5
[e9467ef8] GLMakie v0.5.5

They behave differently because the lookup is done by a shader on the GPU for GLMakie. The reason is that you’re passing a vector with twice the same value, so the automatic color range is computed as (val, val) so the range is 0 wide, which means that linear interpolation of the colormap fails. Pass the known min and max values manually as colorrange = (min, max) to avoid this.

Thanks @jules. I have just tried this code on my windows machine with CairoMakie and it works. On my windows machine, the version of CairoMakie is v0.10.2, while it is v0.7.5 on my Linux machine. I can’t access my Linux machine right now, but I will upgrade CairoMakie next week. I’ll keep you inform.