双三次bezier曲面片代码

以下是双三次Bezier曲面片的示例代码，其中使用了OpenGL和GLUT库来绘制曲面。

#include <GL/glut.h>
#include <iostream>

const int width = 800;
const int height = 800;
GLdouble control_points[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}}};
GLUnurbsObj *nurbsObject;

void display(void) {
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    glPushMatrix();
    glColor3f(1.0, 1.0, 1.0);
    gluBeginSurface(nurbsObject);
    gluNurbsSurface(nurbsObject, 8, knots, 8, knots, 4 * 3, 3, &control_points[0][0][0], 4, 4, GL_MAP2_VERTEX_3);
    gluEndSurface(nurbsObject);
    glPopMatrix();
    glutSwapBuffers();
}

void reshape(int w, int h) {
    glViewport(0, 0, w, h);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    if (w <= h)
        glOrtho(-5.0, 5.0, -5.0 * (GLdouble)h / (GLdouble)w, 5.0 * (GLdouble)h / (GLdouble)w, -5.0, 5.0);
    else
        glOrtho(-5.0 * (GLdouble)w / (GLdouble)h, 5.0 * (GLdouble)w / (GLdouble)h, -5.0, 5.0, -5.0, 5.0);
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();
}

int main(int argc, char **argv) {
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH);
    glutInitWindowSize(width, height);
    glutCreateWindow("Bezier Surface");
    glClearColor(0.0, 0.0, 0.0, 1.0);
    glEnable(GL_DEPTH_TEST);
    glMapGrid2f(20, 0.0, 1.0, 20, 0.0, 1.0);
    nurbsObject = gluNewNurbsRenderer();
    gluNurbsProperty(nurbsObject, GLU_SAMPLING_TOLERANCE, 25.0);
    gluNurbsProperty(nurbsObject, GLU_DISPLAY_MODE, GLU_FILL);
    glutDisplayFunc(display);
    glutReshapeFunc(reshape);
    glutMainLoop();
    return 0;
}