Problems using Gmsh

[Railon69]

Hey folks :)

I am trying to visualize my grid inside bempp or just use one of your standard examples. The problem is that gmsh does not work at all. When I import bempp.api, I get:
Could not find Gmsh.Interactive plotting and shapes module not available.

Therefore, I followed https://bempp.discourse.group/t/fail-to-import-the-package-bempp-api/127/2 using the command

bempp.api.GMSH_PATH = "full/path/to/gmsh/executable"

The error then changes from

RuntimeError: Gmsh is not found. Cannot generate mesh

to

Command 'C:/users/user/wdir/gmsh-4.11.1-Windows64 -2 C:\Users\user\AppData\Local\Temp\tmp9pusbz3w\tmp14z3ffao.geo' returned non-zero exit status 1.

The temp file changes every time I recall the bempp command.
I reinstalled gmsh already. Unfortunately, I couldn't find help neither in the gmsh documentation nor on your side.

bempp.api version = 0.3.0
Gmsh version = 4.11.1

Thanks in advance for your help!

[hjh878]

I have meet such report 'Could not find Gmsh.Interactive plotting and shapes module not available.'. I followed the gmsh website using 'pip install --upgrade gmsh' and such report disappeared

[dvgregor]

Hello Railon69.
I've installed bempp-cl on Windows 10 using this command:
pip install bempp-cl gmsh matplotlib
and got the error 'Could not find Gmsh' you described.

Looks like the error reproduces on Windows only and a workaround could be the following change in C:\Program Files\Python\Python312\Lib\site-packages\bempp\api\external\viewers.py

diff --git a/bempp/api/external/viewers.py b/bempp/api/external/viewers.py
index 19b7b58..27627a5 100644
--- a/bempp/api/external/viewers.py
+++ b/bempp/api/external/viewers.py
@@ -140,6 +140,10 @@ def visualize_with_gmsh(obj, mode=None, transformation=None):
     from bempp.api import export, GMSH_PATH, TMP_PATH, GridFunction
     from bempp.api.grid.grid import Grid

+    print("GMSH_PATH is", GMSH_PATH)
+
+    GMSH_PATH = GMSH_PATH + ".bat"
+
     if GMSH_PATH is None:
         print("Gmsh not available for visualization.")
         return None