[categorial labeling, trame] Workaround for lost legends and axes labels when exported to html / trame

[MarkusZimmerDLR]

Dear pyvista folks,

I am currently struggling with the trame export of pyvista plotters.

More specifically, I am trying to mark and label specific parts of the mesh, either using labels and legends, or labelled axes and cell data.

Legends are lost after html export. Axes labels are converted to integers.
Any idea on how to generate a categorial labelling.

Thanks!

Quick example of the issue:

import pyvista as pv
import numpy as np
s = pv.Sphere()
a = np.arange(s.n_cells, dtype=object)
a[:s.n_cells//2] = 'spam'
a[s.n_cells//2:] = 'egg'
s.cell_data['test'] = a
p = pv.Plotter()
p.add_mesh(s, scalars='test')
p.export_html('test.html')
p.screenshot('test.png')

Result for the png:

Result for html (converted to png for upload):

[MarkusZimmerDLR]

--------------------------------------------------------------------------------
  Date: Fri Dec 01 11:21:55 2023 CET

                  OS : Linux
              CPU(s) : 128
             Machine : x86_64
        Architecture : 64bit
                 RAM : 251.7 GiB
         Environment : IPython
         File system : xfs
          GPU Vendor : Mesa
        GPU Renderer : llvmpipe (LLVM 17.0.1, 256 bits)
         GPU Version : 4.5 (Core Profile) Mesa 23.2.1
    MathText Support : False

  Python 3.12.0 | packaged by conda-forge | (main, Oct  3 2023, 08:43:22) [GCC
  12.3.0]

             pyvista : 0.42.3
                 vtk : 9.2.6
               numpy : 1.26.2
          matplotlib : 3.8.2
              scooby : 0.9.2
               pooch : 1.8.0
              pillow : 10.1.0
             imageio : 2.33.0
           pyvistaqt : 0.11.0
               PyQt5 : 5.15.10
             IPython : 8.18.1
          ipywidgets : 8.1.1
               scipy : 1.11.4
                tqdm : 4.66.1
              meshio : 5.3.4
               trame : 3.3.0
        trame_client : 2.12.7
        trame_server : 2.12.1
           trame_vtk : 2.6.2
       trame_vuetify : 2.3.1
jupyter_server_proxy : 4.1.0
        nest_asyncio : 1.5.8
--------------------------------------------------------------------------------

[banesullivan]

This is unfortunately a limitation of VTK.js and trame-vtk when using the client rendering modes

[MarkusZimmerDLR]

I am seriously interested in a solution.
If there is no workaround to get some kind of categorical labeling, please point in the right direction, so I can create a feature request in the correct repository (vtk.js / trame-vtk).
I am pretty sure I am not the only one with a use case, and this will come up more often in the future.

[jourdain]

The first step would be to add support in vtk.js. Probably in the ScalarBarActor and its implementations WebGL/WebGPU.
Once working on the vtk.js side, we may need to adjust the scene serializer, but it should be pretty straightforward if we have "parity" between the C++ server and the JS client.

[MarkusZimmerDLR]

OK, so I will go ahead and create an FR in the vtk.js repository. However, I am afraid I won't be of mutch help. JS and c++ are not on my strong side.

As mentioned in the first post, legends are also not working yet. But as these are implemented as widgets and widgets are also generally not supported in vtk.js, I do not expect this to be happening any time soon.

However, I want to thank you for the awesome framework you guys have created. It is a blast to work with!

[MarkusZimmerDLR]

I figured. But can you think of any workaround which will enable me to label something in the plot?

[jourdain]

FYI, with trame we are currently working on a VTK/WASM implementation to get the full parity with local rendering.

[MarkusZimmerDLR]

That is a lot to put in one sentence ;) Can you elaborate a little more on what that means for this case? Does that mean you will ditch the vtk.js framework?

[jourdain]

vtk-js will still exist has it provide other benefits than a WASM implementation. But for our usage in trame where we want to mirror a VTK scene that exist on the server side but rendering it on the client side, WASM will give us the full parity that we are currently missing with vtk.js.

[MarkusZimmerDLR]

This. Sounds. Awesome!
Can you guide me to a related issue / repo where I can keep up with updates? I cannot find anything under the pyvista namespace.

[jourdain]

It is currently in development (/private => Kitware/trame-vtklocal) but aimed to be available by the next VTK 9.4 release (April) .
We are still working on C++ and CI.

[kevinalexandr19]

I have the same problem when I try to export a 3D visualization with a title, the title doesn't appear in the HTML export.

[jourdain]

vtk.js does not support text labels hence the issue.