# Wireframe coloring issue: shared boundary between two regions shows mixed colors
**URL:** https://discourse.paraview.org/t/wireframe-coloring-issue-shared-boundary-between-two-regions-shows-mixed-colors/17362
**Category:** ParaView Support
**Tags:** vtk
**Created:** [December 11, 2025, 2:21am UTC](https://discourse.paraview.org/t/wireframe-coloring-issue-shared-boundary-between-two-regions-shows-mixed-colors/17362 "2025-12-11T02:21:34Z")
**Posts on this page:** 11
**Page:** 1
### Author:  [@jialugao](https://discourse.paraview.org/u/jialugao)
#### Post date: [December 11, 2025, 2:21am UTC](https://discourse.paraview.org/t/wireframe-coloring-issue-shared-boundary-between-two-regions-shows-mixed-colors/17362/1 "2025-12-11T02:21:34Z")
Hi everyone,
When visualizing my mesh in Wireframe mode, I color the mesh using a cell-based tag array (for example, region IDs 15 and 16). However, on the shared boundary between the two regions, the edges appear partly in the color of region 15 and partly in the color of region 16.
This results in a “half-and-half” effect on the interface, instead of using a single consistent color along the boundary.
My questions are:
Is this behavior expected in ParaView’s wireframe rendering?
How does ParaView decide which cell’s color is used for a shared edge?
Is there a way to force all shared edges to use the color of one specific region (e.g., region 16)?
I would like the interface between the two regions to show one unified color, not a mixture of both.
Any suggestions or explanations would be greatly appreciated!
Thanks!
[Laplace\_gmsh.xdmf](https://discourse.paraview.org/uploads/short-url/d86fTIhqHHfeDe4gl7vVxLPdeaC.xdmf) (1.1 KB)
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### Author:  [@mwestphal](https://discourse.paraview.org/u/mwestphal)
#### Post date: [December 11, 2025, 8:09am UTC](https://discourse.paraview.org/t/wireframe-coloring-issue-shared-boundary-between-two-regions-shows-mixed-colors/17362/2 "2025-12-11T08:09:01Z")
> [@jialugao](#):
>
> Is this behavior expected in ParaView’s wireframe rendering?
Yes, although it could be improved.
> How does ParaView decide which cell’s color is used for a shared edge?
It probably related to an internal edge ordering
> Is there a way to force all shared edges to use the color of one specific region (e.g., region 16)?
You may be able to achieve better results by splitting the cells entirely
In any case, please share your data (not only the xdmf file)
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### Author:  [@jialugao](https://discourse.paraview.org/u/jialugao)
#### Post date: [December 11, 2025, 8:42am UTC](https://discourse.paraview.org/t/wireframe-coloring-issue-shared-boundary-between-two-regions-shows-mixed-colors/17362/3 "2025-12-11T08:42:58Z")
Hi,
I have uploaded the corresponding **.h5 files** together with the XDMF files so that the full dataset can be loaded properly.
I would also like to ask for clarification regarding the shared-edge coloring issue:
**Do I need to assign explicit physical/region IDs to the common boundary during the mesh generation process?**
If this is required for ParaView to handle shared edges consistently, I can regenerate the mesh and provide a new `.h5` files with the boundary regions explicitly marked.
Thank you for your help, and please let me know if any additional data is needed.
[lagrangian\_mesh.h5](https://discourse.paraview.org/uploads/short-url/2HqiWCB2D7SDfls3fTZuOAsFQTA.h5) (33.5 KB)
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### Author:  [@mwestphal](https://discourse.paraview.org/u/mwestphal)
#### Post date: [December 11, 2025, 8:47am UTC](https://discourse.paraview.org/t/wireframe-coloring-issue-shared-boundary-between-two-regions-shows-mixed-colors/17362/4 "2025-12-11T08:47:01Z")
are you sure this is the right h5 file ? the xdmf file refers to `Laplace_gmsh.h5`
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### Author:  [@jialugao](https://discourse.paraview.org/u/jialugao)
#### Post date: [December 11, 2025, 8:53am UTC](https://discourse.paraview.org/t/wireframe-coloring-issue-shared-boundary-between-two-regions-shows-mixed-colors/17362/5 "2025-12-11T08:53:46Z")
[Laplace\_gmsh.h5](https://discourse.paraview.org/uploads/short-url/51vuNNEo0Y8NO5A4GHjlj9vSIOy.h5) (33.5 KB)
Thanks for pointing this out. I uploaded the wrong `.h5` file by mistake. I’ve now corrected it and uploaded the proper file. Sorry for the confusion.
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### Author:  [@mwestphal](https://discourse.paraview.org/u/mwestphal)
#### Post date: [December 11, 2025, 9:11am UTC](https://discourse.paraview.org/t/wireframe-coloring-issue-shared-boundary-between-two-regions-shows-mixed-colors/17362/6 "2025-12-11T09:11:38Z")
Here you go:
Although I have to save it into an unstructured grid first:
[vtm\_1\_0.vtu](https://discourse.paraview.org/uploads/short-url/a3J2uDFAf8fq0R5L6x3TBa68skP.vtu) (20.5 KB)
And then use ExplodeDataSet
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### Author:  [@jialugao](https://discourse.paraview.org/u/jialugao)
#### Post date: [December 11, 2025, 9:36am UTC](https://discourse.paraview.org/t/wireframe-coloring-issue-shared-boundary-between-two-regions-shows-mixed-colors/17362/7 "2025-12-11T09:36:04Z")
Thank you for your reply. I loaded the `.vtu` file you provided into ParaView, but I cannot find the **ExplodeDataSet** filter in the _Filters_ menu.
Could you please provide the exact steps ?
I may be missing something in the interface.
Thank you again for your help!
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### Author:  [@Kenneth\_Moreland](https://discourse.paraview.org/u/Kenneth_Moreland)
#### Post date: [December 11, 2025, 1:48pm UTC](https://discourse.paraview.org/t/wireframe-coloring-issue-shared-boundary-between-two-regions-shows-mixed-colors/17362/8 "2025-12-11T13:48:35Z")
@mwestphal may have been referring to the `Shrink` filter, which is ironically most often used to create an exploded view of a mesh.
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### Author:  [@mwestphal](https://discourse.paraview.org/u/mwestphal)
#### Post date: [December 11, 2025, 1:51pm UTC](https://discourse.paraview.org/t/wireframe-coloring-issue-shared-boundary-between-two-regions-shows-mixed-colors/17362/9 "2025-12-11T13:51:26Z")
Well, no, I mean the filter called ExplodeDataSet, but its a pretty recent filter only available in 6.0 release of ParaView that you can download here: [https://www.paraview.org/download/](https://www.paraview.org/download/)
It split a dataset into a composite dataset based on the value on the cells.
Here is how to do it:
- Download latest nightly
- File → open → vtm\_1\_0.vtu → Apply
- Filters → ExplodeDataSet → Apply
- Wireframe repr
Shrink is indeed also a solution but requires gap between cells.
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### Author:  [@Kenneth\_Moreland](https://discourse.paraview.org/u/Kenneth_Moreland)
#### Post date: [December 11, 2025, 1:53pm UTC](https://discourse.paraview.org/t/wireframe-coloring-issue-shared-boundary-between-two-regions-shows-mixed-colors/17362/10 "2025-12-11T13:53:58Z")
Yup, my bad. I saw that there is an `Explode Data Set` filter in ParaView 6.0.1 right after I sent off my message.
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### Author:  [@jialugao](https://discourse.paraview.org/u/jialugao)
#### Post date: [December 12, 2025, 2:45am UTC](https://discourse.paraview.org/t/wireframe-coloring-issue-shared-boundary-between-two-regions-shows-mixed-colors/17362/11 "2025-12-12T02:45:31Z")
Thanks for the clarification! I’ll download the latest ParaView build and try it following your steps. Really appreciate the guidance!