occ模型使用osg运行代码示例

使用 OpenSceneGraph (OSG) 运行 OCC 模型的代码示例如下：

#include <osgViewer/Viewer>
#include <osg/Geode>
#include <osg/ShapeDrawable>
#include <osgGA/TrackballManipulator>
#include <osg/MatrixTransform>
#include <osgDB/ReadFile>

#include <BRepPrimAPI_MakeSphere.hxx>
#include <TopoDS.hxx>
#include <TopoDS_Shape.hxx>
#include <BRep_Builder.hxx>
#include <BRepTools.hxx>
#include <BRepTools_WireExplorer.hxx>
#include <BRepBuilderAPI_MakeWire.hxx>
#include <BRepBuilderAPI_MakeFace.hxx>
#include <BRepBuilderAPI_MakePolygon.hxx>
#include <Poly_Triangulation.hxx>
#include <Poly_Connect.hxx>
#include <Poly_Polygon3D.hxx>
#include <TopExp_Explorer.hxx>
#include <TopLoc_Location.hxx>
#include <Poly_Array1OfTriangle.hxx>
#include <BRep_Tool.hxx>
#include <Poly.hxx>

osg::Node* createSphereNode()
{
    TopoDS_Shape shape;
    BRep_Builder builder;
    BRepPrimAPI_MakeSphere sphere(gp_Pnt(0., 0., 0.), 1.);
    shape = sphere.Shape();

    osg::ref_ptr<osg::Geode> geode = new osg::Geode();

    TopExp_Explorer explorer(shape, TopAbs_FACE);
    while (explorer.More())
    {
        TopoDS_Face face = TopoDS::Face(explorer.Current());
        Handle(Poly_Triangulation) polyTri = BRep_Tool::Triangulation(face, TopLoc_Location());
        if (!polyTri.IsNull())
        {
            const TColgp_Array1OfPnt& nodes = polyTri->Nodes();
            const Poly_Array1OfTriangle& triangles = polyTri->Triangles();
            osg::ref_ptr<osg::Vec3Array> vertices = new osg::Vec3Array();
            osg::ref_ptr<osg::DrawElementsUInt> indices = new osg::DrawElementsUInt(osg::PrimitiveSet::TRIANGLES, 0);
            for (Standard_Integer j = triangles.Lower(); j <= triangles.Upper(); j++)
            {
                Standard_Integer n1, n2, n3;
                triangles(j).Get(n1, n2, n3);
                gp_Pnt node1 = nodes(n1);
                gp_Pnt node2 = nodes(n2);
                gp_Pnt node3 = nodes(n3);
                vertices->push_back(osg::Vec3(node1.X(), node1.Y(), node1.Z()));
                vertices->push_back(osg::Vec3(node2.X(), node2.Y(), node2.Z()));
                vertices->push_back(osg::Vec3(node3.X(), node3.Y(), node3.Z()));
                indices->push_back(vertices->size() - 3);
                indices->push_back(vertices->size() - 2);
                indices->push_back(vertices->size() - 1);
            }
            osg::ref_ptr<osg::Geometry> geometry = new osg::Geometry();
            geometry->setVertexArray(vertices);
            geometry->addPrimitiveSet(indices);
            geode->addDrawable(geometry);
        }
        explorer.Next();
    }

    return geode.release();
}

int main(int argc, char** argv)
{
    osg::ref_ptr<osg::Node> model = createSphereNode();

    osgViewer::Viewer viewer;
    viewer.setSceneData(model);
    viewer.setCameraManipulator(new osgGA::TrackballManipulator());
    return viewer.run();
}

在这个示例中，我们创建了一个简单的球体，然后将其转换为 OSG 中的节点，最后将其添加到场景中。我们使用 OCC 库提供的函数来获取球体的三角网格，然后使用 OSG 中的几何体来渲染这个三角网格。最后，我们启动 OSG 视图器并显示场景。

请注意，这只是一个简单的示例，如果要使用 OCC 库加载更复杂的模型，您需要编写更多的代码来处理模型的各个部分。