写一个在mesh模型中添加三维直线约束的代码

下面是在mesh模型中添加三维直线纹理的代码：

#include <iostream>
#include <fstream>
#include <vector>

using namespace std;

struct Point {
    float x, y, z;
};

struct Vertex {
    int pIndex;
    int tIndex;
};

struct TextureCoord {
    float u, v;
};

void addLineIndices(vector<int>& indices, int index1, int index2) {
    indices.push_back(index1);
    indices.push_back(index2);
}

void addLineVertices(vector<Vertex>& vertices, int index1, int index2, int textureIndex) {
    vertices.push_back({ index1, textureIndex });
    vertices.push_back({ index2, textureIndex });
}

void writeMeshToFile(vector<Point>& points, vector<TextureCoord>& textureCoords, vector<Vertex>& vertices, vector<int>& indices, const char* filename) {
    ofstream file(filename);

    file << "g Mesh" << endl;

    // Write vertex positions
    for (int i = 0; i < points.size(); i++) {
        file << "v " << points[i].x << " " << points[i].y << " " << points[i].z << endl;
    }

    // Write texture coordinates
    for (int i = 0; i < textureCoords.size(); i++) {
        file << "vt " << textureCoords[i].u << " " << textureCoords[i].v << endl;
    }

    // Write faces
    for (int i = 0; i < indices.size(); i += 2) {
        int index1 = indices[i];
        int index2 = indices[i + 1];

        file << "f ";
        file << vertices[index1].pIndex + 1 << "/" << vertices[index1].tIndex + 1 << " ";
        file << vertices[index2].pIndex + 1 << "/" << vertices[index2].tIndex + 1 << endl;
    }

    file.close();
}

int main() {
    // Define the points of the line
    vector<Point> points = {
        { 0.0f, 0.0f, 0.0f },
        { 1.0f, 0.0f, 0.0f },
        { 2.0f, 1.0f, 0.0f },
        { 3.0f, 1.0f, 0.0f }
    };

    // Define the texture coordinates for the line
    vector<TextureCoord> textureCoords = {
        { 0.0f, 0.0f },
        { 1.0f, 0.0f },
        { 2.0f, 1.0f },
        { 3.0f, 1.0f }
    };

    // Define the indices for the line
    vector<int> indices;

    addLineIndices(indices, 0, 1);
    addLineIndices(indices, 1, 2);
    addLineIndices(indices, 2, 3);

    // Define the vertices for the line
    vector<Vertex> vertices;

    addLineVertices(vertices, 0, 1, 1);
    addLineVertices(vertices, 1, 2, 2);
    addLineVertices(vertices, 2, 3, 3);

    // Write the mesh to a file
    writeMeshToFile(points, textureCoords, vertices, indices, "line.obj");

    return 0;
}

这个代码将会生成一个名为"line.obj"的OBJ格式的文件，它描述了一个由四个