How can I plot a "slice" of the mesh for a 3D plot?

Question

I'm using NDSolveValue to solve the Laplacian equation for this geometry:

I want to view the mesh that NDSolveValue is using, so I do the following:

Print@Show[
   Graphics3D[{Opacity[0], lrectregion, Opacity[0], rrectregion}, 
    ImageSize -> Large], sol["ElementMesh"]["Wireframe"]];

(where sol is the interpolated function that NDSolveValue returns. Its actual form doesn't matter for this question and the code used to produce it is hefty, so I didn't include it.)

However, it's hard to see what's actually going on in the 3D plot that gets generated:

If I manually zoom in on the boundaries (those rectangles), I can kind of see detail, but still not that well:

I know about these "slice" functions like SliceDensityPlot3D that are very helpful for seeing a 2D "slice" of a 3D function in 3D space. Is there anything like that for visualizing the mesh?

I've looked at this article for element mesh visualization but didn't see anything helpful.

Answer 1

No, there is no SliceDensityPlot3D for mesh visualization. There is no density to plot. The mesh wireframe is a Graphics/Graphics3D object so you can use

sol["ElementMesh"]["Wireframe"[PlotRange -> {All, {40, 60}, All}]]

Show[
   Graphics3D[{Opacity[0], lrectregion, Opacity[0], rrectregion}, 
    ImageSize -> Large], sol["ElementMesh"]["Wireframe"[PlotRange -> {All, {40, 60}, All}]]
,Boxed->False
]

should do what you want.