加载OBJ文件，如何使用法线（#vertices＆lt; #normals）

Question

我有一个obj文件，并且成功地将对象加载到opengl而不使用给定的法线 这就是它的样子：

该文件的格式为：

v x y z
vn x y z
f x//x' y//y' z//z'

网格的显示功能如下：

glBegin(GL_TRIANGLES);
for all faces
{
    glVertex3f(.., .., ..);
    glVertex3f(.., .., ..);
    glVertex3f(.., .., ..);
}
glEnd();

结果如下：

我已经读过，由于OpenGL用于照明方程的默认法线向量，对象可能看起来很平坦 这可以用法线来解决。给出的法线是780，顶点是155.

我尝试在每次glVertex3f调用之前使用glNorm，但是obj看起来很奇怪（行等）。

我该怎么办？

编辑＃1： 这是我阅读文件的方式：

void loader(class mesh &tree)
{
int vx1, vx2, vx3, vn1, vn2, vn3;
ifstream file;
string line;
point vec, norm;
face tempface;

file.open("tree.obj"); 
if (file.is_open() == true)
{
    while(getline(file, line) )
    {
        if (line.substr(0,2) == "") continue;
        else if (line.substr(0, 2) == "v ")
        {
            istringstream numbers(line.substr(2));
            numbers >> vec.x >> vec.y >> vec.z;
            tree.vectors.push_back(vec);
        }
        else if (line.substr(0,2) == "vn")
        {
            istringstream numbers(line.substr(2));
            numbers >> norm.x >> norm.y >> norm.z;
            tree.normals.push_back(norm);
        }
        else if (line.substr(0,2) == "f ")
        {
            face f;
            line = line.substr(2,line.length());
            for (string::iterator it = line.begin(); it != line.end(); ++it)
            {
                if (*it == '/')
                {
                    //erase both of the "//"
                    line.erase(it);
                    line.erase(it);
                    //add a space between the numbers
                    line.insert(it, ' ');
                }
            }
            istringstream inp(line);
            inp >> f.vert_indices[0] >> f.norm_indices[0] >> f.vert_indices[1] >> f.norm_indices[1] >> f.vert_indices[2] >> f.norm_indices[2];
            tree.faces.push_back(f);
        }
        else 
            continue;
    }
    file.close();
}
}

这就是我展示它的方式：

    void mesh::displayMesh()
{
    glPushMatrix();
    glBegin(GL_TRIANGLES);
    for(vector<face>::const_iterator it = faces.begin();
        it != faces.end(); ++it)
    {
        //glVertex3f(normals[it->norm_indices[0] -1 ].x, normals[it->norm_indices[0] -1 ].y, normals[it->norm_indices[0] -1 ].z);
        glVertex3f(vectors[it->vert_indices[0] -1 ].x, vectors[it->vert_indices[0] -1 ].y, vectors[it->vert_indices[0] -1 ].z);
        //glVertex3f(normals[it->norm_indices[1] -1 ].x, normals[it->norm_indices[1] -1 ].y, normals[it->norm_indices[1] -1 ].z);
        glVertex3f(vectors[it->vert_indices[1] -1 ].x, vectors[it->vert_indices[1] -1 ].y, vectors[it->vert_indices[1] -1 ].z);
        //glVertex3f(normals[it->norm_indices[2] -1 ].x, normals[it->norm_indices[2] -1 ].y, normals[it->norm_indices[2] -1 ].z);
        glVertex3f(vectors[it->vert_indices[2] -1 ].x, vectors[it->vert_indices[2] -1 ].y, vectors[it->vert_indices[2] -1 ].z);
    }
    glEnd();
    glPopMatrix();
}

在openGL的Render函数中调用displayMesh函数，并将loader函数调用到Setup OpenGL函数中，并且mesh tree对象是一个全局变量。

编辑＃2： 树如何看待法线：
也是OpenGL设置功能的this is the code。

Answer 1

您的绘图代码中不应该有以下内容吗？

glNormal3f(normals[it->norm_indices[0] -1 ].x, normals[it->norm_indices[0] -1 ].y, normals[it->norm_indices[0] -1 ].z);
glVertex3f(vectors[it->vert_indices[0] -1 ].x, vectors[it->vert_indices[0] -1 ].y, vectors[it->vert_indices[0] -1 ].z);
glNormal3f(normals[it->norm_indices[1] -1 ].x, normals[it->norm_indices[1] -1 ].y, normals[it->norm_indices[1] -1 ].z);
glVertex3f(vectors[it->vert_indices[1] -1 ].x, vectors[it->vert_indices[1] -1 ].y, vectors[it->vert_indices[1] -1 ].z);
glNormal3f(normals[it->norm_indices[2] -1 ].x, normals[it->norm_indices[2] -1 ].y, normals[it->norm_indices[2] -1 ].z);
glVertex3f(vectors[it->vert_indices[2] -1 ].x, vectors[it->vert_indices[2] -1 ].y, vectors[it->vert_indices[2] -1 ].z);

编辑：哎呀，你意识到已经

了

如果要检查法线是否正确，请根据它的正常颜色为每个顶点着色。使用glColor3f但提供法线。

Answer 2

使用erase时，它会使迭代器失效

//erase both of the "//"
it = line.erase(it);
it = line.erase(it);
//add a space between the numbers
it = line.insert(it, ' ');

但是你可以擦除一次然后替换

//erase both of the "//"
it = line.erase(it);
//add a space between the numbers
*it = ' ';