Add Makie contour,contourf, contour! and improve multi-variable plot layout by vincmarks · Pull Request #3088 · trixi-framework/Trixi.jl

vincmarks · 2026-06-17T13:41:35Z

This PR addresses the Makie.jl part of #3075

Added/updated

Makie.contour and Makie.contourf for all mesh types
Makie.contour! adds colored isolines on top of an existing plot
Improved multi-variable plot(pd) layout

Making `plot(pd)` prettier:

I didn't notice, that for plotting solutions with many variables (e.g examples/tree_2d_dgsem/elixir_acoustics_gauss.jl) using plots(pd), plots can currently look like this (Makie.jl)

or like this (Plots.jl)

I tried to make this more pretty in something like this (Makie.jl)

Adding `Makie.contour`, `Makie.contourf` and `Makie.contour!`

Here are some visual results

trixi_include(joinpath(examples_dir(), "unstructured_2d_dgsem",
                       "elixir_acoustics_gauss_wall.jl"))
pd = PlotData2D(sol)

contourf(pd["v1_prime"], plot_mesh = true)

trixi_include(joinpath(examples_dir(), "tree_2d_dgsem", "elixir_acoustics_gauss.jl"))

pd = PlotData2D(sol)

plot(pd["v1_prime"])
contour!(pd["v1_prime"], labels = true)

trixi_include(joinpath(examples_dir(), "tree_2d_dgsem", "elixir_acoustics_gauss.jl"))

pd = PlotData2D(sol)

contourf(pd["v1_prime"])

github-actions · 2026-06-17T13:41:57Z

codecov · 2026-06-17T14:18:17Z

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 96.90%. Comparing base (b6b173e) to head (3761949).

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@@            Coverage Diff             @@
##             main    #3088      +/-   ##
==========================================
+ Coverage   96.88%   96.90%   +0.02%     
==========================================
  Files         647      647              
  Lines       50026    50325     +299     
==========================================
+ Hits        48466    48766     +300     
+ Misses       1560     1559       -1

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vincmarks · 2026-06-19T11:27:03Z

@ranocha, the PR is ready for review

ranocha

Thanks a lot, looks like this is a nice feature! However, this is also a big PR. I did not review everything, but just have a few first comments. Would it make sense to split this into smaller and independent pieces, e.g., improving the existing layout, Cartesian, and other meshes?

ranocha · 2026-06-19T13:06:02Z

+@timed_testset "Makie contour error handling for 1D solutions" begin
+    @test_trixi_include(joinpath(EXAMPLES_DIR, "tree_1d_dgsem",
+                                 "elixir_advection_basic.jl"))
+    @test_throws ArgumentError Makie.contour(sol)
+    @test_throws ArgumentError Makie.tricontourf(sol)
+end


What about 3D solutions?

Oops, I forgot to add them. Thanks!

ranocha · 2026-06-19T13:10:51Z

+# Format colorbar tick labels with enough significant figures to distinguish marks,
+# avoiding Makie's default scientific notation
+function _trixi_colorbar_tickformat(values)
+    isempty(values) && return String[]
+    vmin, vmax = extrema(values)
+    range_val = vmax - vmin
+    sigfigs = range_val > 0 ? max(3, ceil(Int, -log10(range_val)) + 2) : 4
+    return [string(round(v; sigdigits = sigfigs)) for v in values]
+end
+
+# Return a non-degenerate (umin, umax) for colorbars; expands zero-width ranges
+# so CairoMakie does not produce NaN when all data values are identical.
+function _trixi_colorbar_limits(umin, umax)
+    isapprox(umin, umax) || return (umin, umax)
+    delta = max(one(umin), abs(umin))
+    return (umin - delta, umax + delta)
+end
+


Why are these needed, what is wrong with Makie's defaults?

_trixi_colorbar_tickformat: Makie's default tick formatter switches to scientific notation for small values, which I thought were not nice. And with very narrow value ranges, the default rounding can also make adjacent ticks indistinguishable

_trixi_colorbar_limits: This is needed to prevent a crash when all data values are identical (umin == umax). I ran into this with contourf(pd) on elixir_acoustics_gauss_wall.jl, where rho_mean, v1_mean, v2_mean, c_mean are constant (as shown above in the plots). Makie.tricontourf! crashed with "Can't interpolate in a range where cmin == cmax", and similarly CairoMakie produces NaN when constructing a colorbar with a zero-width range.

This sounds like some of them are workarounds for bugs in Makie.jl. Would you mind filing an issue there or creating a PR to fix the bugs there?
Concerning the tick formatter: Could you please post some example where it changes something? What about cases with values varying over several orders of magnitude?

Sure!

Here are some visual results regarding the tick-formatter:

without tick-formatter:

with tick-formatter:

wtithout tick-formatter:

with tick-formatter:

If you prefer it without the tick formatter, I can change the code accordingly.

Look and feel is always a question of taste, but I like your new version for the first example while I prefer the old version for the second example. Is there a discussion in Makie.jl about the first case, where one should arguably not use the scientific notation?

vincmarks · 2026-06-19T14:59:18Z

Thanks a lot, looks like this is a nice feature! However, this is also a big PR. I did not review everything, but just have a few first comments. Would it make sense to split this into smaller and independent pieces, e.g., improving the existing layout, Cartesian, and other meshes?

Yes, I agree, sorry for not following the review checklist guideline of max. 500 lines changed here.
Here's how I'd approach it, if that's more convenient for you:

I already have a backup branch with everything as it should look in the end (modulo changes from review comments ;) ).
I'd scale this PR back to layout improvements only (multi-variable plot(pd)).
Once that's merged, I'll open a second PR for Cartesian contour/contourf/contour!
After that, I'll continue with contour plotting for other meshes.

Does that work for you?

ranocha · 2026-06-19T18:33:55Z

Sounds good, thanks!

vincmarks added 4 commits June 16, 2026 17:59

add contour plotting using Makie

c8c1604

improve plotting in Makie extention

c601f27

Merge branch 'trixi-framework:main' into vm/contour_Makie

482b9f6

format

41a6d8f

vincmarks added 3 commits June 17, 2026 16:39

add tests

4660728

more tests

3761949

Merge branch 'main' into vm/contour_Makie

072418a

vincmarks marked this pull request as ready for review June 19, 2026 11:26

ranocha added enhancement New feature or request visualization labels Jun 19, 2026

ranocha requested changes Jun 19, 2026

View reviewed changes

vincmarks marked this pull request as draft June 22, 2026 15:39

vincmarks mentioned this pull request Jun 23, 2026

Add tricontour recipe, fix contour Colorbar and constant scalar field crashes MakieOrg/Makie.jl#5682

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vincmarks commented Jun 17, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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Added/updated

Making plot(pd) prettier:

Adding Makie.contour, Makie.contourf and Makie.contour!

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github-actions Bot commented Jun 17, 2026

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vincmarks commented Jun 19, 2026

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vincmarks commented Jun 17, 2026 •

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Making `plot(pd)` prettier:

Adding `Makie.contour`, `Makie.contourf` and `Makie.contour!`

codecov Bot commented Jun 17, 2026 •

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ranocha Jun 19, 2026 •

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