OpenCascade Shape Representation in OpenSceneGraph

/*
*    Copyright (c) 2013 eryar All Rights Reserved.
*
*           File : Main.cpp
*         Author : eryar@163.com
*           Date : 2013-12-03 18:09
*        Version : 1.0v
*
*    Description : Draw OpenCascade polygon Curves of the edge
*                  and triangulations of the face in OpenSceneGraph.
*                  When you want to display the shape in the computer,
*                  you can not display the geometry exactly, the only
*                  way to show them is in the approximation form.
*
*      Key Words : OpenCascade, polygon curve, triangulation, 
*                  discrete edge, discrete face, OpenSceneGraph, OSG
*                  
*/

// OpenCascade library.
#define WNT
#include <gp_Circ.hxx>
#include <gp_Elips.hxx>
#include <gp_Sphere.hxx>

#include <Poly_Polygon3D.hxx>
#include <Poly_Triangulation.hxx>

#include <TopoDS_Edge.hxx>
#include <TopoDS_Face.hxx>

#include <BRep_Tool.hxx>
#include <BRepMesh.hxx>
#include <BRepBuilderAPI_MakeEdge.hxx>
#include <BRepBuilderAPI_MakeFace.hxx>

#pragma comment(lib, \"TKernel.lib\")
#pragma comment(lib, \"TKMath.lib\")
#pragma comment(lib, \"TKBRep.lib\")
#pragma comment(lib, \"TKMesh.lib\")
#pragma comment(lib, \"TKTopAlgo.lib\")

// OpenSceneGraph library.
#include <osgDB/ReadFile>
#include <osgViewer/Viewer>
#include <osgGA/StateSetManipulator>
#include <osgViewer/ViewerEventHandlers>

#pragma comment(lib, \"osgd.lib\")
#pragma comment(lib, \"osgDBd.lib\")
#pragma comment(lib, \"osgGAd.lib\")
#pragma comment(lib, \"osgViewerd.lib\")

/*
* @breif Descret the shape: edge.
*        For Edge will be discreted to polylines; (GCPnts_TangentialDeflection)
*        To get the polyline of the edge, use BRep_Tool::Polygon3D(Edge, L);
*/
osg::Node* BuildPolyline(const TopoDS_Edge& edge, double deflection = 0.1)
{
    osg::ref_ptr<osg::Geode> geode = new osg::Geode();
    osg::ref_ptr<osg::Geometry> linesGeom = new osg::Geometry();
    osg::ref_ptr<osg::Vec3Array> pointsVec = new osg::Vec3Array();

    TopLoc_Location location;

    BRepMesh::Mesh(edge, deflection);
    Handle_Poly_Polygon3D polyline = BRep_Tool::Polygon3D(edge, location);

    for (int i = 1; i < polyline->NbNodes(); i++)
    {
        gp_Pnt point = polyline->Nodes().Value(i);

        pointsVec->push_back(osg::Vec3(point.X(), point.Y(), point.Z()));
    }

    // Set the color of the polyline.
    osg::ref_ptr<osg::Vec4Array> colors = new osg::Vec4Array;
    colors->push_back(osg::Vec4(1.0f, 1.0f, 0.0f, 0.0f));
    linesGeom->setColorArray(colors.get());
    linesGeom->setColorBinding(osg::Geometry::BIND_OVERALL);

    // Set vertex array.
    linesGeom->setVertexArray(pointsVec);
    linesGeom->addPrimitiveSet(new osg::DrawArrays(osg::PrimitiveSet::LINE_LOOP, 0, pointsVec->size()));
    
    geode->addDrawable(linesGeom.get());

    return geode.release();
}

/*
* @breif Descret the shape: face.
*        For Face will be discreted to triangles; (BRepMesh_FastDiscret)
*        To get the triangles of the face, use BRep_Tool::Triangulation(Face, L);
*/
osg::Node* BuildMesh(const TopoDS_Face& face, double deflection = 0.1)
{
    osg::ref_ptr<osg::Geode> geode = new osg::Geode();
    osg::ref_ptr<osg::Geometry> triGeom = new osg::Geometry();
    osg::ref_ptr<osg::Vec3Array> vertices = new osg::Vec3Array();
    osg::ref_ptr<osg::Vec3Array> normals = new osg::Vec3Array();

    TopLoc_Location location;
    BRepMesh::Mesh(face, deflection);

    Handle_Poly_Triangulation triFace = BRep_Tool::Triangulation(face, location);

    Standard_Integer nTriangles = triFace->NbTriangles();

    gp_Pnt vertex1;
    gp_Pnt vertex2;
    gp_Pnt vertex3;

    Standard_Integer nVertexIndex1 = 0;
    Standard_Integer nVertexIndex2 = 0;
    Standard_Integer nVertexIndex3 = 0;

    TColgp_Array1OfPnt nodes(1, triFace->NbNodes());
    Poly_Array1OfTriangle triangles(1, triFace->NbTriangles());

    nodes = triFace->Nodes();
    triangles = triFace->Triangles();       

    for (Standard_Integer i = 1; i <= nTriangles; i++)
    {
        Poly_Triangle aTriangle = triangles.Value(i);
        
        aTriangle.Get(nVertexIndex1, nVertexIndex2, nVertexIndex3);

        vertex1 = nodes.Value(nVertexIndex1).Transformed(location.Transformation());
        vertex2 = nodes.Value(nVertexIndex2).Transformed(location.Transformation());
        vertex3 = nodes.Value(nVertexIndex3).Transformed(location.Transformation());

        gp_XYZ vector12(vertex2.XYZ() - vertex1.XYZ());
        gp_XYZ vector13(vertex3.XYZ() - vertex1.XYZ());
        gp_XYZ normal = vector12.Crossed(vector13);
        Standard_Real rModulus = normal.Modulus();

        if (rModulus > gp::Resolution())
        {
            normal.Normalize();
        }
        else
        {
            normal.SetCoord(0., 0., 0.);
        }

        //if (face.Orientable() != TopAbs_FORWARD)
        //{
        //    normal.Reverse();
        //}

        vertices->push_back(osg::Vec3(vertex1.X(), vertex1.Y(), vertex1.Z()));
        vertices->push_back(osg::Vec3(vertex2.X(), vertex2.Y(), vertex2.Z()));
        vertices->push_back(osg::Vec3(vertex3.X(), vertex3.Y(), vertex3.Z()));

        normals->push_back(osg::Vec3(normal.X(), normal.Y(), normal.Z()));
    }

    triGeom->setVertexArray(vertices.get());
    triGeom->addPrimitiveSet(new osg::DrawArrays(osg::PrimitiveSet::TRIANGLES, 0, vertices->size()));

    triGeom->setNormalArray(normals);
    triGeom->setNormalBinding(osg::Geometry::BIND_PER_PRIMITIVE);

    geode->addDrawable(triGeom);

    return geode.release();
}

osg::Node* BuildScene(void)
{
    osg::ref_ptr<osg::Group> root = new osg::Group();

    gp_Ax2 axis;

    // 1. Test circle while deflection is default 0.1;
    TopoDS_Edge circleEdge1 = BRepBuilderAPI_MakeEdge(gp_Circ(axis, 6.0));
    root->addChild(BuildPolyline(circleEdge1));

    // 2. Test circle while deflection is 0.001.
    axis.SetLocation(gp_Pnt(8.0, 0.0, 0.0));
    axis.SetDirection(gp_Dir(1.0, 1.0, 1.0));

    TopoDS_Edge circleEdge2 = BRepBuilderAPI_MakeEdge(gp_Circ(axis, 6.0));
    root->addChild(BuildPolyline(circleEdge2, 0.001));

    // 3. Test ellipse while deflection is 1.0.
    TopoDS_Edge ellipseEdge = BRepBuilderAPI_MakeEdge(gp_Elips(gp::XOY(), 16.0, 8.0));
    root->addChild(BuildPolyline(ellipseEdge, 1.0));

    // 4. Test sphere face while deflection is default 0.1.
    axis.SetLocation(gp_Pnt(26.0, 0.0, 0.0));
    TopoDS_Face sphereFace1 = BRepBuilderAPI_MakeFace(gp_Sphere(axis, 8.0));
    root->addChild(BuildMesh(sphereFace1));

    // 5. Test sphere face while deflection is 2.0.
    axis.SetLocation(gp_Pnt(26.0, 18.0, 0.0));
    TopoDS_Face sphereFace2 = BRepBuilderAPI_MakeFace(gp_Sphere(axis, 8.0));
    root->addChild(BuildMesh(sphereFace2, 2.0));

    // 6. Test sphere face while deflection is 0.001.
    axis.SetLocation(gp_Pnt(26.0, -18.0, 0.0));
    TopoDS_Face sphereFace3 = BRepBuilderAPI_MakeFace(gp_Sphere(axis, 8.0));
    root->addChild(BuildMesh(sphereFace3, 0.001));

    return root.release();
}

int main(void)
{
    osgViewer::Viewer myViewer;

    myViewer.setSceneData(BuildScene());

    myViewer.addEventHandler(new osgGA::StateSetManipulator(myViewer.getCamera()->getOrCreateStateSet()));
    myViewer.addEventHandler(new osgViewer::StatsHandler);
    myViewer.addEventHandler(new osgViewer::WindowSizeHandler);

    return myViewer.run();
}