#include <GL/glut.h>

//定義控制點(diǎn)points
GLfloat ctrlpoints[4][4][3] = {
    { {1.0,2.4,0.8},{1.1,0.6,0.4}, {1.2,0.2,0.0},{2.0,-1.0,0.4}},//points0 

    { {2.6,1.0,0.8},{2.8,-0.4,0.4},{3.0,-0.8,0.0},{3.8,-1.6,0.4}},//points1

    { {5.2,1.0,0.0},{5.4,-0.4,0.0},{5.6,-0.8,0.0},{6.4,-1.6,0.0}},//points2
    
    { {7.4,2.4,0.0},{7.4,0.6,0.0},{7.8,0.2,0.0},{8.8,-0.6,0.2}} //points3
};

/* Nurbs曲面的對象指針 */
GLUnurbsObj  *theNurb;

void display(void)
{
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    //清楚顏色緩沖
    glColor3f(0.0, 0.0, 0.0);
    //glPushMatrix()和glPopMatrix()的配對使用可以消除上一次的變換對本次變換的影響
    glPushMatrix();

    //繪制控制線
    glLineWidth(1.5f); //設(shè)置線寬1.5
    glColor3f(0.0, 0.0, 1.0); //設(shè)置線顏色為藍(lán)色
    for (int i = 0; i < 4; i++)
    {
        //設(shè)置類型為連續(xù)直線
        glBegin(GL_LINE_STRIP);
        //繪制列向的控制線
        for (int j = 0; j < 4; j++)
            glVertex3fv(ctrlpoints[i][j]);
        glEnd();
        //繪制橫向的控制線
        glBegin(GL_LINE_STRIP);
        for (int j = 0; j < 4; j++)
            glVertex3fv(ctrlpoints[j][i]);
        glEnd();
    }

    //繪制控制點(diǎn)
    glPointSize(5.0f); //設(shè)置點(diǎn)的大小為5.0
    glColor3f(1.0, 0.0, 0.0); //設(shè)置點(diǎn)顏色為紅色
    glBegin(GL_POINTS); //模式為POINTS
    for (int i = 0; i < 4; i++)
    {
        for (int j = 0; j < 4; j++)
        {
            glVertex3fv(ctrlpoints[i][j]);
        }
    }
    glEnd();

    //繪制B樣條控制曲面
    GLfloat knots[8] = { 0.0,0.0,0.0,0.0,1.0,1.0,1.0,1.0 }; //B樣條控制向量
    glLineWidth(1.0f); //設(shè)置線寬為1.0
    glColor3f(0.0, 0.0, 0.0); //線的顏色為黑色

    /* 創(chuàng)建一個Nurbs曲面的對象  并返回一個指向這個新對象的指針 */
    theNurb = gluNewNurbsRenderer();
    /* 設(shè)置該對象的屬性 */
    gluNurbsProperty(theNurb, GLU_SAMPLING_TOLERANCE, 25.0); 
    gluNurbsProperty(theNurb, GLU_DISPLAY_MODE, GLU_OUTLINE_POLYGON);
    gluBeginSurface(theNurb);//開始繪制
    gluNurbsSurface(theNurb, //NURBS曲面對象
        8, knots,  //u向節(jié)點(diǎn)數(shù)目和節(jié)點(diǎn)數(shù)組指針
        8, knots,  //v向節(jié)點(diǎn)數(shù)目和節(jié)點(diǎn)數(shù)組指針
        4 * 3,  //u向的跨度 列優(yōu)先保存 t_stride = 4 * s_count
        3,   //v向的跨度
        &ctrlpoints[0][0][0], //曲面控制點(diǎn)指針
        4, 4, //u方向弟头、v方向階數(shù)
        GL_MAP2_VERTEX_3 //曲面的類型
    );

    gluEndSurface(theNurb); //結(jié)束繪制

    for (int j = 0; j <= 8; j++)
    {
        glBegin(GL_LINE_STRIP);
        for (int i = 0; i <= 30; i++)
            glEvalCoord2f((GLfloat)i / 30.0, (GLfloat)j / 8.0);
        glEnd();
        glBegin(GL_LINE_STRIP);
        for (int i = 0; i <= 30; i++)
            glEvalCoord2f((GLfloat)j / 8.0, (GLfloat)i / 30.0);
        glEnd();
    }
    
    glPopMatrix();
    glFlush();
}

void reshape(int w, int h) 
{ 
    glViewport(0, 0, (GLsizei)w, (GLsizei)h); /* 設(shè)置觀察窗口的大小 */ 
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    /* 設(shè)置正投影, 6個參數(shù)分別表示, 左修剪平面坐標(biāo), 右修剪平面坐標(biāo), 
    下修剪平面坐標(biāo), 上修剪平面坐標(biāo), 近修剪平面坐標(biāo), 遠(yuǎn)修剪平面坐標(biāo) */
    glOrtho(0.0, 10.0, -5.0 * (GLfloat)h / (GLfloat)w, 
        5.0 * (GLfloat)h / (GLfloat)w, -5.0, 5.0); 
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();
}

void init(void)
{
    glClearColor(1.0, 1.0, 1.0, 0.0);
    //激活該曲面函數(shù)
    glEnable(GL_MAP2_VERTEX_3); 
}

int main(int argc, char** argv)
{
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB |
        GLUT_DEPTH);
    glutInitWindowSize(500, 500);
    glutInitWindowPosition(100, 100);
    glutCreateWindow(argv[0]);
    init();
    glutReshapeFunc(reshape);
    glutDisplayFunc(display);
    glutMainLoop();
    return 0;
}