import os import tempfile import warnings import numpy as np from ..constants import log from ..typed import Integer, Number, Optional # the old `gmsh-sdk` package is deprecated and # has a different incompatible API! _min_gmsh = (4, 12, 1) _warning = " ".join( [ "`trimesh.interfaces.gmsh` is deprecated and will be removed January 2025!", "There are *many* gmsh options on PyPi: `scikit-gmsh` `gmsh` `pygmsh` `gmsh-sdk`,", "users should pick one of those and use it directly. If STEP loading is the only", "thing needed you may want `pip install cascadio` which uses OpenCASCADE more", "directly and will immediately enable STEP as a loadable format in trimesh.", ] ) def load_gmsh(file_name, gmsh_args=None, interruptible=True): """ Returns a surface mesh from CAD model in Open Cascade Breap (.brep), Step (.stp or .step) and Iges formats Or returns a surface mesh from 3D volume mesh using gmsh. For a list of possible options to pass to GMSH, check: http://gmsh.info/doc/texinfo/gmsh.html An easy way to install the GMSH SDK is through the `gmsh` package on PyPi, which downloads and sets up gmsh: >>> pip install gmsh Parameters -------------- file_name : str Location of the file to be imported gmsh_args : (n, 2) list List of (parameter, value) pairs to be passed to gmsh.option.setNumber max_element : float or None Maximum length of an element in the volume mesh interruptible : bool Allows load_gmsh to run outside of the main thread if False, default behaviour if set to True. Added in 4.12.0 Returns ------------ mesh : trimesh.Trimesh Surface mesh of input geometry """ warnings.warn(_warning, category=DeprecationWarning, stacklevel=2) # use STL as an intermediate format # do import here to avoid very occasional segfaults import gmsh # the deprecated `pip install gmsh-sdk` package has an entirely different API # require a minimum version here if tuple(int(i) for i in gmsh.__version__.split(".")) < _min_gmsh: raise ImportError( f"`gmsh.__version__ < {_min_gmsh}`: run `pip install --upgrade gmsh`" ) from ..exchange.stl import load_stl # start with default args for the meshing step # Mesh.Algorithm=2 MeshAdapt/Delaunay, there are others but they may include quads # With this planes are meshed using Delaunay and cylinders are meshed # using MeshAdapt args = [ ("Mesh.Algorithm", 2), ("Mesh.CharacteristicLengthFromCurvature", 1), ("Mesh.MinimumCirclePoints", 32), ] # add passed argument tuples last so we can override defaults if gmsh_args is not None: args.extend(gmsh_args) # formats GMSH can load supported = [ ".brep", ".stp", ".step", ".igs", ".iges", ".bdf", ".msh", ".inp", ".diff", ".mesh", ] # check extensions to make sure it is supported format if file_name is not None: if not any(file_name.lower().endswith(e) for e in supported): raise ValueError( "Supported formats are: BREP (.brep), STEP (.stp or .step), " + "IGES (.igs or .iges), Nastran (.bdf), Gmsh (.msh), Abaqus (*.inp), " + "Diffpack (*.diff), Inria Medit (*.mesh)" ) else: raise ValueError("No import since no file was provided!") # hmmm init = False try: if hasattr(gmsh, "isInitialized"): init = gmsh.isInitialized() elif hasattr(gmsh, "is_initialized"): init = gmsh.is_initialized() except BaseException: log.debug("gmsh unexpected", exc_info=True) if not init: gmsh.initialize(interruptible=interruptible) gmsh.option.setNumber("General.Terminal", 1) gmsh.model.add("Surface_Mesh_Generation") # loop through our numbered args which do things, stuff for arg in args: gmsh.option.setNumber(*arg) gmsh.open(file_name) # create a temporary file for the results out_data = tempfile.NamedTemporaryFile(suffix=".stl", delete=False) # windows gets mad if two processes try to open the same file out_data.close() # we have to mesh the surface as these are analytic BREP formats if any( file_name.lower().endswith(e) for e in [".brep", ".stp", ".step", ".igs", ".iges"] ): gmsh.model.geo.synchronize() # generate the mesh gmsh.model.mesh.generate(2) # write to the temporary file gmsh.write(out_data.name) else: gmsh.plugin.run("NewView") gmsh.plugin.run("Skin") gmsh.view.write(1, out_data.name) # load the data from the temporary outfile with open(out_data.name, "rb") as f: kwargs = load_stl(f) gmsh.finalize() return kwargs def to_volume( mesh, file_name: Optional[str] = None, file_type: Optional[str] = None, max_element: Optional[Number] = None, mesher_id: Integer = 1, ) -> bytes: """ Convert a surface mesh to a 3D volume mesh generated by gmsh. An easy way to install the gmsh sdk is through the gmsh package on pypi, which downloads and sets up gmsh: pip install gmsh Algorithm details, although check gmsh docs for more information: The "Delaunay" algorithm is split into three separate steps. First, an initial mesh of the union of all the volumes in the model is performed, without inserting points in the volume. The surface mesh is then recovered using H. Si's boundary recovery algorithm Tetgen/BR. Then a three-dimensional version of the 2D Delaunay algorithm described above is applied to insert points in the volume to respect the mesh size constraints. The Frontal" algorithm uses J. Schoeberl's Netgen algorithm. The "HXT" algorithm is a new efficient and parallel reimplementaton of the Delaunay algorithm. The "MMG3D" algorithm (experimental) allows to generate anisotropic tetrahedralizations Parameters -------------- mesh : trimesh.Trimesh Surface mesh of input geometry file_type Location to save output, in .msh (gmsh) or .bdf (Nastran) format max_element : float or None Maximum length of an element in the volume mesh mesher_id : int 3D unstructured algorithms: 1: Delaunay, 3: Initial mesh only, 4: Frontal, 7: MMG3D, 9: R-tree, 10: HXT Returns ------------ data : None or bytes MSH data, only returned if file_name is None """ warnings.warn(_warning, category=DeprecationWarning, stacklevel=2) # do import here to avoid very occasional segfaults import gmsh if tuple(int(i) for i in gmsh.__version__.split(".")) < _min_gmsh: raise ImportError( f"`gmsh.__version__ < {_min_gmsh}`: run `pip install --upgrade gmsh`" ) # checks mesher selection if mesher_id not in [1, 3, 4, 7, 9, 10]: raise ValueError("unavailable mesher selected!") else: mesher_id = int(mesher_id) # set max element length to a best guess if not specified if max_element is None: max_element = np.sqrt(np.mean(mesh.area_faces)) if file_name is not None: file_type = file_name.split(".")[-1].lower() elif file_type is not None: file_type = file_type.lower().strip(".") else: file_type = "msh" if file_type not in ["bdf", "msh", "inp", "diff", "mesh"]: raise ValueError( "Only Nastran (`bdf`), Gmsh (`msh`), Abaqus (`inp`), " + "Diffpack (`diff`) and Inria Medit (`mesh`) formats " + "are available!" ) # use a temporary directory for input and output with tempfile.TemporaryDirectory() as D: mesh_file = os.path.join(D, "input.stl") mesh.export(mesh_file) # starts Gmsh Python API script gmsh.initialize() gmsh.option.setNumber("General.Terminal", 1) gmsh.model.add("Nastran_stl") gmsh.merge(mesh_file) dimtag = gmsh.model.getEntities()[0] dim = dimtag[0] tag = dimtag[1] surf_loop = gmsh.model.geo.addSurfaceLoop([tag]) gmsh.model.geo.addVolume([surf_loop]) gmsh.model.geo.synchronize() # We can then generate a 3D mesh... gmsh.option.setNumber("Mesh.Algorithm3D", mesher_id) gmsh.option.setNumber("Mesh.CharacteristicLengthMax", max_element) gmsh.model.mesh.generate(3) dimtag2 = gmsh.model.getEntities()[1] dim2 = dimtag2[0] tag2 = dimtag2[1] p2 = gmsh.model.addPhysicalGroup(dim2, [tag2]) gmsh.model.setPhysicalName(dim, p2, "Nastran_bdf") out_path = os.path.join(D, f"temp.{file_type}") gmsh.write(out_path) with open(out_path, "rb") as f: data = f.read() # close up shop gmsh.finalize() # write the data if file_name is not None: with open(os.path.abspath(os.path.expanduser(file_name)), "wb") as f: f.write(data) return data