same question

[XuankeShi]

you can try the data： std::vector ver = { -0.5f, 1.f, 0.f, 0.5f, 1.f, 0.f, 1.f, 0.f, 0.f, 0.5f, -1.f, 0.f, -0.5f, -1.f, 0.f, -1.f, 0.f, 0.f, 0.f, 0.f, 0.f }; std::vector tri = { 1, 2, 7, 7, 2 ,3, 3, 4, 7, 7, 4, 5, 7, 5, 6, 7, 6, 1 }; for(auto &a : tri) { a--; }

[XuankeShi]

i think i have understand your code.

[yig]

So does it work for you now?

[XuankeShi]

i can run the code . but i think the code can't sovle the question which tiangles index is out of order.

you can try this obj file . i only change 1 triangle index sequence.
provide your email. i can send it to you

------------------ 原始邮件 ------------------ 发件人: "yig/halfedge" <[email protected]>; 发送时间: 2020年10月21日(星期三) 晚上6:07 收件人: "yig/halfedge"<[email protected]>; 抄送: "Xuanke Shi"<[email protected]>;"Author"<[email protected]>; 主题: Re: [yig/halfedge] same question (#2)

So does it work for you now?

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[yig]

I can compile the following file via c++ -o example example.cpp trimesh.cpp -std=c++11. It runs and prints:

neighbors of vertex 0:  5 6 1
neighbors of vertex 1:  0 6 2
neighbors of vertex 2:  1 6 3
neighbors of vertex 3:  2 6 4
neighbors of vertex 4:  3 6 5
neighbors of vertex 5:  4 6 0
neighbors of vertex 6:  0 5 4 3 2 1

example.cpp:

#include <iostream>
#include <vector>
#include "trimesh.h"
// #include "trimesh.cpp"

/*
$ ./example
neighbors of vertex 0:  5 6 1
neighbors of vertex 1:  0 6 2
neighbors of vertex 2:  1 6 3
neighbors of vertex 3:  2 6 4
neighbors of vertex 4:  3 6 5
neighbors of vertex 5:  4 6 0
neighbors of vertex 6:  0 5 4 3 2 1
*/

int main( int argc, char* argv[] )
{
    std::vector<float> ver = {
    -0.5f, 1.f, 0.f,
    0.5f, 1.f, 0.f,
    1.f, 0.f, 0.f,
    0.5f, -1.f, 0.f,
    -0.5f, -1.f, 0.f,
    -1.f, 0.f, 0.f,
    0.f, 0.f, 0.f
    };
    std::vector<long> triangles = {
    1, 2, 7,
    7, 2 ,3,
    3, 4, 7,
    7, 4, 5,
    7, 5, 6,
    7, 6, 1
    };
    for(auto &a : triangles) {
    a--;
    }
    
    std::vector< trimesh::edge_t > edges;
    trimesh::unordered_edges_from_triangles( triangles.size()/3, reinterpret_cast<const trimesh::triangle_t*>( &triangles[0] ), edges );
    
    trimesh::trimesh_t mesh;
    mesh.build( ver.size()/3, triangles.size()/3, reinterpret_cast<const trimesh::triangle_t*>( &triangles[0] ), edges.size(), &edges[0] );
    
    // Use 'mesh' to walk the connectivity.
    std::vector< trimesh::index_t > neighs;
    for( int vi = 0; vi < ver.size()/3; ++vi )
    {
        mesh.vertex_vertex_neighbors( vi, neighs );
        
        std::cout << "neighbors of vertex " << vi << ": ";
        for( int i = 0; i < neighs.size(); ++i )
        {
            std::cout << ' ' << neighs.at(i);
        }
        std::cout << '\n';
    }
    
    return 0;
}

[XuankeShi]

I can compile the following file via c++ -o example example.cpp trimesh.cpp -std=c++11. It runs and prints:

neighbors of vertex 0:  5 6 1
neighbors of vertex 1:  0 6 2
neighbors of vertex 2:  1 6 3
neighbors of vertex 3:  2 6 4
neighbors of vertex 4:  3 6 5
neighbors of vertex 5:  4 6 0
neighbors of vertex 6:  0 5 4 3 2 1

example.cpp:

#include <iostream>
#include <vector>
#include "trimesh.h"
// #include "trimesh.cpp"

/*
$ ./example
neighbors of vertex 0:  5 6 1
neighbors of vertex 1:  0 6 2
neighbors of vertex 2:  1 6 3
neighbors of vertex 3:  2 6 4
neighbors of vertex 4:  3 6 5
neighbors of vertex 5:  4 6 0
neighbors of vertex 6:  0 5 4 3 2 1
*/

int main( int argc, char* argv[] )
{
    std::vector<float> ver = {
    -0.5f, 1.f, 0.f,
    0.5f, 1.f, 0.f,
    1.f, 0.f, 0.f,
    0.5f, -1.f, 0.f,
    -0.5f, -1.f, 0.f,
    -1.f, 0.f, 0.f,
    0.f, 0.f, 0.f
    };
    std::vector<long> triangles = {
    1, 2, 7,
    7, 2 ,3,
    3, 4, 7,
    7, 4, 5,
    7, 5, 6,
    7, 6, 1
    };
    for(auto &a : triangles) {
    a--;
    }
    
    std::vector< trimesh::edge_t > edges;
    trimesh::unordered_edges_from_triangles( triangles.size()/3, reinterpret_cast<const trimesh::triangle_t*>( &triangles[0] ), edges );
    
    trimesh::trimesh_t mesh;
    mesh.build( ver.size()/3, triangles.size()/3, reinterpret_cast<const trimesh::triangle_t*>( &triangles[0] ), edges.size(), &edges[0] );
    
    // Use 'mesh' to walk the connectivity.
    std::vector< trimesh::index_t > neighs;
    for( int vi = 0; vi < ver.size()/3; ++vi )
    {
        mesh.vertex_vertex_neighbors( vi, neighs );
        
        std::cout << "neighbors of vertex " << vi << ": ";
        for( int i = 0; i < neighs.size(); ++i )
        {
            std::cout << ' ' << neighs.at(i);
        }
        std::cout << '\n';
    }
    
    return 0;
}

sorry ， i made a mistake. maybe u can try the triangles as follows, it means the triangles' normal direction are different. std::vector triangles = { 1, 2, 7, 2, 7 ,3, 3, 4, 7, 7, 4, 5, 7, 5, 6, 7, 6, 1 };

[yig]

If the triangles have inconsistent orientation, you can't use a halfedge data structure. What happens when you try it?

On Oct 21, 2020, at 2:42 PM, 史璇珂 [email protected] wrote:

I can compile the following file via c++ -o example example.cpp trimesh.cpp -std=c++11. It runs and prints:

neighbors of vertex 0: 5 6 1 neighbors of vertex 1: 0 6 2 neighbors of vertex 2: 1 6 3 neighbors of vertex 3: 2 6 4 neighbors of vertex 4: 3 6 5 neighbors of vertex 5: 4 6 0 neighbors of vertex 6: 0 5 4 3 2 1 example.cpp:

#include #include #include "trimesh.h" // #include "trimesh.cpp"

/* $ ./example neighbors of vertex 0: 5 6 1 neighbors of vertex 1: 0 6 2 neighbors of vertex 2: 1 6 3 neighbors of vertex 3: 2 6 4 neighbors of vertex 4: 3 6 5 neighbors of vertex 5: 4 6 0 neighbors of vertex 6: 0 5 4 3 2 1 */

int main( int argc, char* argv[] ) { std::vector ver = { -0.5f, 1.f, 0.f, 0.5f, 1.f, 0.f, 1.f, 0.f, 0.f, 0.5f, -1.f, 0.f, -0.5f, -1.f, 0.f, -1.f, 0.f, 0.f, 0.f, 0.f, 0.f }; std::vector triangles = { 1, 2, 7, 7, 2 ,3, 3, 4, 7, 7, 4, 5, 7, 5, 6, 7, 6, 1 }; for(auto &a : triangles) { a--; }

std::vector< trimesh::edge_t > edges;
trimesh::unordered_edges_from_triangles( triangles.size()/3, reinterpret_cast<const trimesh::triangle_t*>( &triangles[0] ), edges );

trimesh::trimesh_t mesh;
mesh.build( ver.size()/3, triangles.size()/3, reinterpret_cast<const trimesh::triangle_t*>( &triangles[0] ), edges.size(), &edges[0] );

// Use 'mesh' to walk the connectivity.
std::vector< trimesh::index_t > neighs;
for( int vi = 0; vi < ver.size()/3; ++vi )
{
    mesh.vertex_vertex_neighbors( vi, neighs );
    
    std::cout << "neighbors of vertex " << vi << ": ";
    for( int i = 0; i < neighs.size(); ++i )
    {
        std::cout << ' ' << neighs.at(i);
    }
    std::cout << '\n';
}

return 0;

} sorry ， i made a mistake. maybe u can try the triangles as follows, it means the triangles' normal direction are different. std::vector triangles = { 1, 2, 7, 2, 7 ,3, 3, 4, 7, 7, 4, 5, 7, 5, 6, 7, 6, 1 };

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[XuankeShi]

If the triangles have inconsistent orientation, the code runs error because the directed edge are same. i think your implemention is a simplified version，it has some limitation for example ,in the obj file.you can change the triangles' index sequence by yourself. but it should not influence the initialization of the halfedge structure.

[XuankeShi]

If the triangles have inconsistent orientation, the code runs error because the directed edge are same. i think your implemention is a simplified version，it has some limitation for example ,in the obj file.you can change the triangles' index sequence by yourself. but it should not influence the initialization of the halfedge structure.

Maybe you're right, i firstly touch the halfedge data structure. thanks for your reply.