Question

加载.off文件很容易：

typedef CGAL::Simple_cartesian<double>  Kernel;
typedef CGAL::Surface_mesh<Kernel::Point_3> SurfaceMesh;
typedef CGAL::Polyhedron_3<Kernel> Polyhedron;

...

SurfaceMesh surface;
Polyhedron poly;
std::fstream inputOffFile( "myFile.off" );
inputOffFile >> poly;
CGAL::copy_face_graph( poly, surface);

然后，我可以通过以下方式迭代顶点坐标：

std::vector<float> verts;
for( SurfaceMesh::Vertex_index vi : surface.vertices() )
{
    Point pt = surface.point( vi );
    verts.push_back( pt.x() );
    verts.push_back( pt.y() );
    verts.push_back( pt.z() );
}

但是我该如何访问存储在.off文件中的顶点颜色呢？

编辑：可能CGAL :: copy_face_graph不复制color属性，所以我想我需要其他方法？

Answer 1

您需要使用SurfaceMesh的属性映射。当且仅当OFF文件具有颜色（意味着第一个指示为COFF而不是第一行为OFF），并且每个顶点且不仅每个面都有颜色时，SurfaceMesh才会具有一个内部属性图，称为“ v：颜色”。您可以通过调用

进行访问

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如果每个面都有颜色，则可以通过搜索名为“ f：color”的属性图来类似地访问它。您可以使用surface.property_map <......>（...）。second检查地图是否存在。

Answer 2

好的，这是完整的解决方案，包括访问面顶点（如果要通过OpenGL渲染网格，则需要此权限）。使用SurfaceMesh是关键。

...
std::vector<Point> verts;
std::vector<Color> cols;

SurfaceMesh::Property_map<SurfaceMesh::Vertex_index, CGAL::Color> vcolors =
    m_pSurface->property_map<SurfaceMesh::Vertex_index, CGAL::Color >( "v:color" ).first;

bool colorExists = m_pSurface->property_map<SurfaceMesh::Vertex_index, CGAL::Color>( "v:color" ).second;

if( !colorExists ) 
    Error(); 

for( SurfaceMesh::Vertex_index vi : m_pSurface->vertices() )
{
    cols.push_back( vcolors[ vi ] );
    verts.push_back( m_pSurface->point( vi ) );
}

for( SurfaceMesh::Face_index face_index : m_pSurface->faces() )
{
    CGAL::Vertex_around_face_circulator<SurfaceMesh> vcirc( m_pSurface->halfedge( face_index ), *m_pSurface ), done( vcirc );

    signed char count = 0;

    do
    {
        count++;
        uint32_t vertexI = *vcirc++;

        const Point &pt = verts[ vertexI ];
        const Color &col = cols[ vertexI ];

        ...

    } while( vcirc != done );

}

非常感谢您的有用评论！

CGAL：加载.off文件后如何访问顶点颜色？

2 个答案: