vtkRenderer background color ignored on initial rendering in local mode

[ppebay]

Description:

When using vtkRenderer in a Trame application with local mode using a SinglePageWithDrawerLayout instance, the specified background color is not displayed on initial rendering with no data. Instead, the background appears white until the user interacts with the UI, after which the correct background color is rendered.

In contrast, in remote mode, the proper background color appears initially as expected.

Environment:

System: macOS Sonoma 14.3
Browser: Chrome
VTK Version: 9.4.2 (pip)
Trame Version: 3.8.2 (pip)
Trame-VTK version: 2.8.15 (pip)

Notes:

This appears to be a timing or render sync issue specific to local mode rendering. It may be related to VtkRemoteLocalView not triggering an initial render or the render window not being fully initialized at the moment SetBackground() is called.

[jourdain]

This is a known issue, the scene does not get serialized if no actor is present within the renderer. In other words, the renderer is not even present on the client side since it is empty.

Moving forward, local rendering should be done using wasm (trame-vtklocal).

[ppebay]

Should VtkRemoteLocalView with mode=local be abandoned altogether then?

[jourdain]

Once the wasm one is fully mature, yes. For now, the vtk.js implementation is ok with some limitations.

[ppebay]

And regarding the SinglePlageWithDrawerLayout, I noticed other small issues in local mode: for instance, setting EdgeVisibilityOn() in an actor's properties that is not loaded upfront, but later in the process, is consistently ignored until it is toggled Off/On -- at which point edges become visible. With the same pipeline settings but in remote mode, none of these problems surface (no pun intended).

[jourdain]

There is no relationship to SinglePlageWithDrawerLayout, but it is possible that the local mode has some sync glitch.

[ppebay]

Alright, thanks for the update on the potential local mode sync problems.

As you mentioned earlier that, going forward, trame-vtklocal will be the way to go for local rendering, is it safe to assume that none of the currently observed synchronization issues in local mode won't be fixed in the vtk.js implementation?

[jourdain]

Correct unless you make PR for those. Most of the code is in this repo, unless a fix is required on the vtk.js side.

[jourdain]

And to clarify, switching the implementation is just 2 lines change (import + class instantiation).