An openFOAM-tailored OBJ exporter for FreeCAD

openfoam_obj_exporter.py

#***************************************************************************
#*                                                                         *
#*   Copyright (c) 2015                                                    *
#*   Yorik van Havre <yorik@uncreated.net>                                 *
#*                                                                         *
#*   This program is free software; you can redistribute it and/or modify  *
#*   it under the terms of the GNU Lesser General Public License (LGPL)    *
#*   as published by the Free Software Foundation; either version 2 of     *
#*   the License, or (at your option) any later version.                   *
#*   for detail see the LICENCE text file.                                 *
#*                                                                         *
#*   This program is distributed in the hope that it will be useful,       *
#*   but WITHOUT ANY WARRANTY; without even the implied warranty of        *
#*   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the         *
#*   GNU Library General Public License for more details.                  *
#*                                                                         *
#*   You should have received a copy of the GNU Library General Public     *
#*   License along with this program; if not, write to the Free Software   *
#*   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  *
#*   USA                                                                   *
#*                                                                         *
#***************************************************************************

__title__ =  "FreeCAD openfoam-ready OBJ importer"
__author__ = "Yorik van Havre"
__url__ =    "http://www.freecadweb.org"

import FreeCAD,FreeCADGui,DraftGeomUtils,Part,MeshPart

# below is a safeguard in case we redefine "open" later in this script
if open.__module__ == '__builtin__':
    pythonopen = open
    
def export(exportlist,filename,tessellation=1,scaling=0.001,mesher="builtin",\
           grading=0.3,segperedge=1,segperradius=2,secondorder=0,optimize=1,allowquad=0):
    """export(exportlist,filename,tessellation=1,scaling=0.001,mesher="builtin",
    grading=0.3,segperedge=1,segperradius=2,secondorder=0,optimize=1,allowquad=0): 
    exports the given objects list to the given OBJ filename. The objects will be
    exported with separate regions defined by face color. Using smaller
    tessellation values will result in coarser meshes. mesher can be builtin,
    mefisto or netgen. Attributes after mesher are only used for netgen"""
    
    def triangulate(face):
        "triangulates the given face"
        if mesher == "builtin":
            return face.tessellate(tessellation)
        elif mesher == "mefisto":
            return MeshPart.meshFromShape(Shape=face,MaxLength=tessellation).Topology
        elif mesher == "netgen":
            return MeshPart.meshFromShape(Shape=face,GrowthRate=grading,SegPerEdge=segperedge,SegPerRadius=segperradius,SecondOrder=secondorder,Optimize=optimize,AllowQuad=allowquad).Topology
    
    # build a dictionary of faces sorted by color
    colordict = {}
    for obj in exportlist:
        if obj.isDerivedFrom("Part::Feature"):
            sh = obj.Shape.cleaned()
            if sh.Faces:
                if len(obj.ViewObject.DiffuseColor) == len(sh.Faces):
                    # per-face colors are defined
                    for i in range(len(obj.ViewObject.DiffuseColor)):
                        colordict.setdefault(obj.ViewObject.DiffuseColor[i],[]).append(sh.Faces[i])
                else:
                    # one color for whole object
                    for f in sh.Faces:
                        colordict.setdefault(obj.ViewObject.ShapeColor,[]).append(f)
                
    if not colordict:
        FreeCAD.Console.PrintError("Unable to retrieve color information from the given objects\n")
        return
        
    # build a dictionary of vectors
    temp = {}
    vectorsdict = {}
    offset = 1
    for color,faces in colordict.items():
        temp[color] = []
        for f in faces:
            # test the need for triangulation
            tris = None
            for e in f.Edges:
                if not isinstance(e.Curve,Part.Line):
                    # there are curved edges
                    if not tris:
                        tris = triangulate(f)
            if len(f.Wires) > 1:
                # there is a hole in this face
                tris = triangulate(f)
            if tris:
                # triangulating the face
                for f in tris[1]:
                    findex = []
                    for i in f:
                        if tuple(tris[0][i]) in vectorsdict:
                            findex.append(vectorsdict[tuple(tris[0][i])])
                        else:
                            vectorsdict[tuple(tris[0][i])] = offset
                            findex.append(offset)
                            offset += 1
                    temp[color].append(findex)
            else:
                # no triangulation
                findex = []
                # OCC vertex list can be in wrong order, we sort them here
                edges = DraftGeomUtils.sortEdges(f.OuterWire.Edges)
                for e in edges:
                    v = e.Vertexes[0].Point
                    if tuple(v) in vectorsdict:
                        findex.append(vectorsdict[tuple(v)])
                    else:
                        vectorsdict[tuple(v)] = offset
                        findex.append(offset)
                        offset += 1
                temp[color].append(findex)
    colordict = temp
    
    # debug
    print "vectors:     ",vectorsdict
    print "facegroups:  ",colordict
    
    # write the obj file
    outfile = pythonopen(filename,"wb")
    ver = FreeCAD.Version()
    outfile.write("# FreeCAD v" + ver[0] + "." + ver[1] + " build" + ver[2] + " OpenFOAM exporter\n")
    outfile.write("# http://www.freecadweb.org\n")
    
    # sort and write verts first
    vecs = vectorsdict.keys()
    l = sorted(range(len(vecs)),key=lambda x:vectorsdict.values()[x])
    vecs = [vecs[i] for i in l]
    for v in vecs:
        outfile.write("v " + str(v[0]*scaling) + " " + str(v[1]*scaling) + " " + str(v[2]*scaling) + "\n")

    # write color groups
    idx = 1
    for color,faces in colordict.items():
        # build a group name from the color data
        outfile.write("g patch" + str(idx) + "\n")
        # write face indexes
        for f in faces:
            outfile.write("f")
            for i in f:
                outfile.write(" " + str(i))
            outfile.write("\n")
        idx += 1
    outfile.close()
    FreeCAD.Console.PrintMessage("Successfully exported "+filename+"\n")