Witht e followng script I attempt at explaning the issue/request.
I am trying to generate an extruded mesh in gmsh using a 3d solid (obtained by extrusion) in an assembly:
import assembly_mesh_plugin
from cadquery import Workplane, Assembly
if __name__ == "__main__":
obj = (Workplane()
.rect(10, 10)
.extrude(5)
)
obj.faces("-Z").tag("back").end()
assy = Assembly()
# main object
assy.add(obj, name="main")
# get into gmsh
gmsh = assy.getTaggedGmsh()
# tagged face is there
pg = "main_back"
print(f"Physical group '{pg}' from tag:")
dimtags = gmsh.model.getEntitiesForPhysicalName(pg)
print()
# clean up physical groups
gmsh.model.removePhysicalGroups()
gmsh.model.addPhysicalGroup(dimtags[0][0], [dt[1] for dt in dimtags], name="back")
# mesh is not extruded
gmsh.model.mesh.generate(3)
gmsh.fltk.run()The issue is that gmsh doesn't now the body was extruded, so the mesh is not extruded:
The goal would be to inform gmsh that the body is extruded (and how many elements it should put in the extrusion direction), to get a mesh like this:
which is done by extending the previous script with:
# New model with tagged entity only
# get lines then points
_, lines = gmsh.model.getAdjacencies(*dimtags[0])
pts = []
for l in lines:
_, pts_ = gmsh.model.getAdjacencies(1, l)
p1 = gmsh.model.getValue(0, pts_[1], [])
pts.append(p1)
# new model
gmsh.model.add("extruded")
# rebuild face
pts_tag = []
for p in pts:
pts_tag.append(gmsh.model.occ.addPoint(*p))
lin_tag = []
for p0, p1 in zip([pts_tag[-1]]+pts_tag[:-1], pts_tag):
lin_tag.append(gmsh.model.occ.addLine(p0, p1))
loop_tag = gmsh.model.occ.addCurveLoop(lin_tag)
surf_tag = gmsh.model.occ.addPlaneSurface([loop_tag])
# rebuild physical group
gmsh.model.addPhysicalGroup(2, [surf_tag], name="back")
gmsh.model.occ.extrude(
[[2,surf_tag]],
dx=0,
dy=0,
dz=10,
numElements=[1],
recombine=True,
)
gmsh.model.occ.synchronize()
gmsh.model.mesh.generate(3)
gmsh.fltk.run()
gmsh.finalize()My approach
Currently I am building a workaround to rebuild the extruded solid and the correspoding physical groups.
In the example above I tagged the surface I used to extrude, but in the general problem lateral surfaces can also be tagged.
For example ,"+X" faces with tag "side".
So what I do in this case, when the second gmsh model (named "extruded" in the code above) is extruded I compare the coordinates of the surfaces with those of the tagged surfaces in the original model, and add a physical group to the extruded model with the corresponding entities. Quite a hack! ... and brittle.
Do you have a better idea?
Witht e followng script I attempt at explaning the issue/request.
I am trying to generate an extruded mesh in gmsh using a 3d solid (obtained by extrusion) in an assembly:
The issue is that gmsh doesn't now the body was extruded, so the mesh is not extruded:
The goal would be to inform gmsh that the body is extruded (and how many elements it should put in the extrusion direction), to get a mesh like this:
which is done by extending the previous script with:
My approach
Currently I am building a workaround to rebuild the extruded solid and the correspoding physical groups.
In the example above I tagged the surface I used to extrude, but in the general problem lateral surfaces can also be tagged.
For example ,"+X" faces with tag "side".
So what I do in this case, when the second gmsh model (named "extruded" in the code above) is extruded I compare the coordinates of the surfaces with those of the tagged surfaces in the original model, and add a physical group to the extruded model with the corresponding entities. Quite a hack! ... and brittle.
Do you have a better idea?