7.5.5编程实例－Bezier曲线曲面绘制

（a）Bezier曲线 (b) Bezier曲面 1. 绘制Bezier曲线

#include <GL/glut.h> GLfloat ctrlpoints[4][3] = {{ -4.0, -4.0, 0.0}, { -2.0, 3.0, 0.0}, {2.0, 4.5, 0.0}, {3.0, -3.0, 0.0}}; void init(void) { glClearColor(1.0, 1.0, 1.0, 0.0); glShadeModel(GL_FLAT); //下行用于定义曲线函数 glMap1f(GL_MAP1_VERTEX_3, 0.0, 1.0, 3, 4, &ctrlpoints[0][0]); glEnable(GL_MAP1_VERTEX_3); //将当前曲线函数激活 } void display(void) { int i; glClear(GL_COLOR_BUFFER_BIT); //下面用求值器按20等分计算Bezier曲线上的点 glColor3f(0.0, 0.0, 0.0); glLineWidth(2); glBegin(GL_LINE_STRIP); for (i = 0; i <= 20; i++) glEvalCoord1f((GLfloat) i/20.0); //相当于调用了glVertex*() glEnd(); //下面绘制控制多边形 glLineWidth(1); glColor3f(0.0, 0.0, 1.0); glBegin(GL_LINE_STRIP); for (i = 0; i < 4; i++) glVertex3fv(&ctrlpoints[i][0]); glEnd(); glFlush(); } void reshape(int w, int h) { glViewport(0, 0, (GLsizei) w, (GLsizei) h); glMatrixMode(GL_PROJECTION); glLoadIdentity(); if (w <= h) glOrtho(-5.0, 5.0, -5.0*(GLfloat)h/(GLfloat)w, 5.0*(GLfloat)h/(GLfloat)w, -5.0, 5.0); else glOrtho(-5.0*(GLfloat)w/(GLfloat)h, 5.0*(GLfloat)w/(GLfloat)h, -5.0, 5.0, -5.0, 5.0); glMatrixMode(GL_MODELVIEW); glLoadIdentity(); } int main(int argc, char** argv) { glutInit(&argc, argv); glutInitDisplayMode (GLUT_SINGLE | GLUT_RGB); glutInitWindowSize (500, 500); glutInitWindowPosition (100, 100); glutCreateWindow (argv[0]); init (); glutDisplayFunc(display); glutReshapeFunc(reshape); glutMainLoop(); return 0; } 2. 绘制Bezier曲面 #include <GL/glut.h> GLfloat ctrlpoints[4][4][3] = { {{-3, 0, 4.0}, {-2, 0, 2.0}, {-1, 0, 0.0}, {0, 0, 2.0}}, {{-3, 1, 1.0}, {-2, 1, 3.0}, {-1, 1, 6.0}, {0, 1, -1.0}}, {{-3, 2, 4.0}, {-2, 2, 0.0}, {-1, 2, 3.0}, {0, 2, 4.0}}, {{-3, 3, 0.0}, {-2, 3, 0.0}, {-1, 3, 0.0}, {0, 3, 0.0}} }; void display(void) { int i, j; glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); glColor3f(0.0, 0.0, 0.0); glPushMatrix (); glRotatef(85.0, 1.0, 1.0, 1.0); for (j = 0; j <= 20; j++) { glBegin(GL_LINE_STRIP); for (i = 0; i <= 20; i++) glEvalCoord2f((GLfloat)i/20.0, (GLfloat)j/20.0); //调用求值器 glEnd(); glBegin(GL_LINE_STRIP); for (i = 0; i <= 20; i++) glEvalCoord2f((GLfloat)j/20.0, (GLfloat)i/20.0); //调用求值器 glEnd(); } glPopMatrix (); glFlush(); } void init(void) { glClearColor (1.0, 1.0, 1.0, 0.0); //下行的代码用控制点定义Bezier曲面函数 glMap2f(GL_MAP2_VERTEX_3, 0, 1, 3, 4, 0, 1, 12, 4, &ctrlpoints[0][0][0]); glEnable(GL_MAP2_VERTEX_3); //激活该曲面函数 glOrtho(-5.0, 5.0, -5.0, 5.0, -5.0, 5.0); //构造平行投影矩阵 } 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); glutMainLoop(); return 0; }