调用opengl写一个三次控制贝塞尔曲面代码

以下是一个简单的OpenGL三次控制贝塞尔曲面的代码示例：

#include <GL/glut.h>

GLfloat ctrlpoints[4][4][3] = {
    {{-1.5, -1.5, 4.0}, {-0.5, -1.5, 2.0}, 
     {0.5, -1.5, -1.0}, {1.5, -1.5, 2.0}}, 
    {{-1.5, -0.5, 1.0}, {-0.5, -0.5, 3.0}, 
     {0.5, -0.5, 0.0}, {1.5, -0.5, -1.0}}, 
    {{-1.5, 0.5, 4.0}, {-0.5, 0.5, 0.0}, 
     {0.5, 0.5, 3.0}, {1.5, 0.5, 4.0}}, 
    {{-1.5, 1.5, -2.0}, {-0.5, 1.5, -2.0}, 
     {0.5, 1.5, 0.0}, {1.5, 1.5, -1.0}}
};

void display(void)
{
    int i, j;
    
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    glColor3f(1.0, 1.0, 1.0);
    glPushMatrix();
    glRotatef(85.0, 1.0, 1.0, 1.0);
    for (j = 0; j <= 8; j++) {
        glBegin(GL_LINE_STRIP);
        for (i = 0; i <= 30; i++)
            glEvalCoord2f((GLfloat)i/30.0, (GLfloat)j/8.0);
        glEnd();
        glBegin(GL_LINE_STRIP);
        for (i = 0; i <= 30; i++)
            glEvalCoord2f((GLfloat)j/8.0, (GLfloat)i/30.0);
        glEnd();
    }
    glPopMatrix();
    glFlush();
}

void init(void)
{
    glClearColor(0.0, 0.0, 0.0, 0.0);
    glShadeModel(GL_FLAT);
    glEnable(GL_DEPTH_TEST);
    glMap2f(GL_MAP2_VERTEX_3, 0.0, 1.0, 3, 4, 
            0.0, 1.0, 12, 4, &ctrlpoints[0][0][0]);
    glEnable(GL_MAP2_VERTEX_3);
    glEnable(GL_AUTO_NORMAL);
    glMapGrid2f(20, 0.0, 1.0, 20, 0.0, 1.0);
}

void reshape(int w, int h)
{
    glViewport(0, 0, (GLsizei)w, (GLsizei)h);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    if (w <= h)
        glOrtho(-4.0, 4.0, -4.0*(GLfloat)h/(GLfloat)w, 
                4.0*(GLfloat)h/(GLfloat)w, -4.0, 4.0);
    else
        glOrtho(-4.0*(GLfloat)w/(GLfloat)h, 
                4.0*(GLfloat)w/(GLfloat)h, -4.0, 4.0, -4.0, 4.0);
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();
}

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();
    glutDisplayFunc(display);
    glutReshapeFunc(reshape);
    glutMainLoop();
    return 0;
}

在该代码中，通过`ctrlpoints`定义了4*4个控制点，然后使用OpenGL的`glMap2f`函数设置了一个三次贝塞尔曲面的顶点数组。使用`glMapGrid2f`函数来设置细分数，并使用`glEvalCoord2f`函数来对曲面进行求值，并使用`glBegin`和`glEnd`函数来绘制连续的线段。通过调整相机视角，可以更好地观察贝塞尔曲面。