readOBJ.C

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/*---------------------------------------------------------------------------*\
  =========                 |
  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
   \\    /   O peration     | Website:  https://openfoam.org
    \\  /    A nd           | Copyright (C) 2011-2025 OpenFOAM Foundation
     \\/     M anipulation  |
-------------------------------------------------------------------------------
License
    This file is part of OpenFOAM.
 
    OpenFOAM is free software: you can redistribute it and/or modify it
    under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.
 
    OpenFOAM 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 General Public License
    for more details.
 
    You should have received a copy of the GNU General Public License
    along with OpenFOAM.  If not, see <http://www.gnu.org/licenses/>.
 
\*---------------------------------------------------------------------------*/
 
#include "triSurface.H"
#include "IFstream.H"
#include "IStringStream.H"
 
// * * * * * * * * * * * * * * * Member Functions  * * * * * * * * * * * * * //
 
bool Foam::triSurface::readOBJ(const fileName& OBJfileName)
{
    IFstream OBJfile(OBJfileName);
 
    if (!OBJfile.good())
    {
        FatalErrorInFunction
            << "Cannot read file " << OBJfileName
            << exit(FatalError);
    }
 
    DynamicList<point> points;
    DynamicList<labelledTri> faces;
    HashTable<label> groupToPatch;
 
    label groupID = 0;
    label maxGroupID = 0;
 
    while (OBJfile.good())
    {
        const string line = getLineNoComment(OBJfile);
 
        // Read first word
        IStringStream lineStream(line);
        word cmd;
        lineStream >> cmd;
 
        if (cmd == "v")
        {
            scalar x, y, z;
 
            lineStream >> x >> y >> z;
 
            points.append(point(x, y, z));
        }
        else if (cmd == "g")
        {
            word group;
 
            lineStream >> group;
 
            HashTable<label>::const_iterator findGroup =
                groupToPatch.find(group);
 
            if (findGroup != groupToPatch.end())
            {
                groupID = findGroup();
            }
            else
            {
                groupID = maxGroupID;
 
                groupToPatch.insert(group, groupID);
 
                maxGroupID++;
            }
        }
        else if (cmd == "f")
        {
            DynamicList<label> verts;
 
            // Assume 'f' is followed by space.
            string::size_type endNum = 1;
 
            while (true)
            {
                string::size_type startNum =
                    line.find_first_not_of(" \r", endNum);
 
                if (startNum == string::npos)
                {
                    break;
                }
 
                endNum = line.find(' ', startNum);
 
                string vertexSpec;
                if (endNum != string::npos)
                {
                    vertexSpec = line.substr(startNum, endNum-startNum);
                }
                else
                {
                    vertexSpec = line.substr(startNum, line.size() - startNum);
                }
 
                string::size_type slashPos = vertexSpec.find('/');
 
                label vertI = 0;
                if (slashPos != string::npos)
                {
                    IStringStream intStream(vertexSpec.substr(0, slashPos));
 
                    intStream >> vertI;
                }
                else
                {
                    IStringStream intStream(vertexSpec);
 
                    intStream >> vertI;
                }
                verts.append(vertI - 1);
            }
 
            verts.shrink();
 
            // Do simple face triangulation around f[0].
            // Cannot use face::triangulation since no complete points yet.
            for (label fp = 1; fp < verts.size() - 1; fp++)
            {
                label fp1 = verts.fcIndex(fp);
 
                labelledTri tri(verts[0], verts[fp], verts[fp1], groupID);
 
                faces.append(tri);
            }
        }
    }
 
    points.shrink();
    faces.shrink();
 
    // Convert groupToPatch to patchList.
    geometricSurfacePatchList patches(maxGroupID);
 
    if (maxGroupID == 0)
    {
        // Generate default patch
        patches.setSize(1);
        patches[0] = geometricSurfacePatch("empty", "patch0", 0);
    }
    else
    {
        forAllConstIter(HashTable<label>, groupToPatch, iter)
        {
            patches[iter()] = geometricSurfacePatch
            (
                "empty",
                iter.key(),
                iter()
            );
        }
    }
 
 
    // Transfer DynamicLists to straight ones.
    pointField allPoints(move(points));
 
    // Create triSurface
    *this = triSurface(faces, patches, allPoints, true);
 
    return true;
}
 
 
// ************************************************************************* //