使用PMP（Polygon Mesh Processing）库进行网格细分

Question

我正在使用 PMP（多边形网格处理）库来执行网格细分。首先，我使用函数 mesh.add_vertex_property('v:position') 添加了一个名为“position”（称为属性 1）的动态属性。此属性的值与存储在 mesh.positions() 中的值相同（称为属性 2）。进行细分处理后，发现属性1和属性2的数据几乎相等，但是传递给VBO（Vertex Buffer Object）时只有属性2的数据可以用于渲染，而属性1的数据无法呈现。没有进一步的信息，这个问题的原因尚不清楚。

我的主要功能是

Assimp::Importer importer;
const aiScene* scene = importer.ReadFile("bun_zipper.ply", aiProcess_Triangulate | aiProcess_GenNormals);

    pmp::SurfaceMesh mesh_;
    auto normals = mesh_.add_vertex_property<pmp::Normal>("v:normal");
    auto positions = mesh_.add_vertex_property<pmp::Point>("v:position");
    auto originPositions = mesh_.add_vertex_property<pmp::vec3>("v:oriPos");
    if (!scene || scene->mFlags & AI_SCENE_FLAGS_INCOMPLETE || !scene->mRootNode)
    {
        cout << !scene << endl;
        cout << "ERROR::ASSIMP:: " << importer.GetErrorString() << endl;
        return 0;
    }
    int num = 0;
    for (unsigned int i = 0; i < scene->mNumMeshes; i++) 
    {
        const aiMesh* mesh = scene->mMeshes[i];
     
        std::vector<pmp::Vertex> vertices;
        for (unsigned int k = 0; k < mesh->mNumVertices; k++) 
        {
            aiVector3D pos = mesh->mVertices[k];
            aiVector3D normal = mesh->mNormals[k];
            pmp::Vertex v = mesh_.add_vertex(pmp::Point(pos.x, pos.y, pos.z));
            positions[v] = pmp::Point(pos.x, pos.y, pos.z);
            originPositions[v] = pmp::vec3(pos.x, pos.y, pos.z);
            normals[v] = pmp::Normal(normal.x, normal.y, normal.z);
    
            vertices.push_back(v);
        }
        
        for (unsigned int k = 0; k < mesh->mNumFaces; k++)
        {
            const aiFace& face = mesh->mFaces[k];
            if (face.mNumIndices != 3)
            {
                cout << face.mNumIndices;
            }
                mesh_.add_triangle(vertices[face.mIndices[0]], vertices[face.mIndices[1]], vertices[face.mIndices[2]]);
          }
    
    }
    
    pmp::Subdivision subdivision(mesh_);
    subdivision.loop();
    auto oripos = mesh_.get_vertex_property<pmp::vec3>("v:oriPos");
    auto norm = mesh_.get_vertex_property<pmp::Normal>("v:normal");
        for (unsigned int k = 0; k < mesh->mNumFaces; k++)
        {
            const aiFace& face = mesh->mFaces[k];
            if (face.mNumIndices != 3)
            {
                cout << face.mNumIndices;
            }
              mesh_.add_triangle(vertices[face.mIndices[0]],vertices[face.mIndices[1]],vertices[face.mIndices[2]]);
          }
    
    }
    pmp::Subdivision subdivision(mesh_);
    subdivision.loop();
    auto oripos = mesh_.get_vertex_property<pmp::vec3>("v:oriPos");
    auto norm = mesh_.get_vertex_property<pmp::Normal>("v:normal");
    std::vector<GLfloat> vertices;
    for (auto v : mesh_.vertices()) {
        vertices.push_back(oripos[v][0]);
        vertices.push_back(oripos[v][1]);
        vertices.push_back(oripos[v][2]);
        vertices.push_back(norm[v][0]);
        vertices.push_back(norm[v][1]);
        vertices.push_back(norm[v][2]);
        
    }
    std::vector<GLuint> indices;
    for (auto face: mesh_.faces())
    {
        for (auto v : mesh_.vertices(face))
        {
            indices.push_back(v.idx());
        }
    }
    
    
    Shader lineShader("bunny_shader.vert", "bunny_line_shader.fs");
    
    unsigned int VAO, VBO, EBO;
    glGenVertexArrays(1, &VAO);
    glGenBuffers(1, &VBO);
    glGenBuffers(1, &EBO);
    
    glBindVertexArray(VAO);
    glBindBuffer(GL_ARRAY_BUFFER, VBO);
    glBufferData(GL_ARRAY_BUFFER, sizeof(GLfloat) * vertices.size(), vertices.data(), GL_STATIC_DRAW);
    glEnableVertexAttribArray(0);
    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, sizeof(GLfloat) * 6, (void*)(0));
    glEnableVertexAttribArray(1);
    glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, sizeof(GLfloat) * 6, (void*)(sizeof(GLfloat) * 3));
    glBindBuffer(GL_ARRAY_BUFFER, 0);
    
    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, EBO);
    glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(GLfloat)* indices.size(), indices.data(), GL_STATIC_DRAW);
    
    glEnable(GL_DEPTH_TEST);
    glEnable(GL_CULL_FACE);

while (!glfwWindowShouldClose(window))
{
float currentFrame = static_cast\<float\>(glfwGetTime());
deltaTime = currentFrame - lastFrame;
lastFrame = currentFrame;
processInput(window);
glClearColor(0.5, 0.5, 0.5, 1.0);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

        lineShader.use();
        glm::mat4 projection = glm::perspective(glm::radians(camera.Zoom), (float)SCR_WIDTH / (float)SCR_HEIGHT, 0.1f, 100.0f);
        glm::mat4 view = camera.getViewMat();
        lineShader.setMat4("projection", projection);
        lineShader.setMat4("view", view);
        glm::mat4 model1 = glm::mat4(1.0f);
    
        model1 = glm::rotate(model1, glm::radians(180.0f), glm::vec3(0.0f, 0.0f, 1.0f));
        model1 = glm::scale(model1, glm::vec3(1.0f, 1.0f, 1.0f));
        lineShader.setMat4("model", model1);
        glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);
        glBindVertexArray(VAO);
        glDrawElements(GL_TRIANGLES,static_cast<unsigned int>(indices.size()),GL_UNSIGNED_INT,0);
        glfwPollEvents();
    
        glfwSwapBuffers(window);
    }

属性一和属性二的代码唯一不同的是，从mesh_中导入了数据

std::vector<GLfloat> vertices

，如下： 属性一（无法渲染）

    std::vector<GLfloat> vertices;
    for (auto v : mesh_.vertices()) {
        vertices.push_back(oripos[v][0]);
        vertices.push_back(oripos[v][1]);
        vertices.push_back(oripos[v][2]);
        vertices.push_back(norm[v][0]);
        vertices.push_back(norm[v][1]);
        vertices.push_back(norm[v][2]);
    }

属性二（可渲染）

    std::vector<GLfloat> vertices;
    for (auto v : mesh_.vertices()) {
        vertices.push_back(mesh_.position(v)[0]);
        vertices.push_back(mesh_.position(v)[1]);
        vertices.push_back(mesh_.position(v)[2]);
        vertices.push_back(norm[v][0]);
        vertices.push_back(norm[v][1]);
        vertices.push_back(norm[v][2]);
    }