计算机图形学裁剪【计算机图形学实验四 :裁剪】
贵州大学实验报告
学院：计算机科学与技术 专业： 计算机科学与技术 班级：计科131
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glColor3f(0.0f, 1.0f, 0.0f); glVertex2f(x1, y1); glEnd(); }
//矩形的结构体
typedef struct Rectangle {
float xmin; float xmax; float ymin; float ymax; } Rectan ;
Rectan rect;
int x0, y0, x1, y1;
//求出坐标点的Cohen-Sutherland 编码
int CompCode(int x , int y , Rectan rect ) {
int code = 0x00; if (y
code = code | 4; }
if (y >rect .ymax) {
code = code | 8; }
if (x >rect .xmax) {
code = code | 2; }
if (x
code = code | 1; }
return code; }
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//裁剪直线
int cohensutherlandlineclip(Rectan rect , int & x0, int & y0, int & x1, int & y1) {
int accept = 0, done = 0; float x, y;
int code0, code1, codeout;
int x00 = x0, y00 = y0, x11 = x1, y11 = y1;
code0 = CompCode(x0, y0, rect ); code1 = CompCode(x1, y1, rect );
//直线全部在矩形框内部，应保留 if (!(code0 | code1)) {
accept = 1; done = 1; }
//直线和矩形不相交，并且划直线的两点在矩形同侧（上、下、右。左），应去掉。 if (code0 & code1) {
done = 1; }
while (!done) {
//直线和矩形有交点，只保留矩形内部的 if (!(code0 | code1)) {
accept = 1; done = 1; } else {
if (code0 != 0) {
codeout = code0; } else {
codeout = code1; }
if (codeout & LEFT_EDGE)
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{
y = y0 + (y1 - y0)*(rect .xmin - x0) / (x1 - x0); x = (float ) rect .xmin; } else {
if (codeout &RIGHT_EDGE) {
y = y0 + (y1 - y0)*(rect .xmax - x0) / (x1 - x0); x = (float ) rect .xmax; } else {
if (codeout & BOTTOM_EDGE) {
x = y0 + (x1 - x0)*(rect .ymin - y0) / (y1 - y0); y = (float ) rect .ymin; } else {
if (codeout & TOP_EDGE) {
x = x0 + (x1 - x0)*(rect .ymax - y0) / (y1 - y0); y = (float ) rect .ymax; } } } }
if (codeout == code0) {
x0 = x; y0 = y;
code0 = CompCode(x0, y0, rect ); } else {
x1 = x; y1 = y;
code1 = CompCode(x1, y1, rect ); }
//直线和矩形不相交，但是划直线的两点在矩形不同侧，这时应去掉。 if ((times
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{
x0 = x1; y0 = y1; done = 1; accept = 1; } } }
if (accept) {
LineGL(x0, y0, x1, y1); }
return accept; }
void myDisplay() {
glClear(GL_COLOR_BUFFER_BIT); glColor3f(1.0f, 1.0f, 0.0f);
glRectf(rect.xmin, rect.ymin, rect.xmax, rect.ymax);
LineGL(x0, y0, x1, y1);
glFlush(); }
void Init() {
glClearColor(0.0, 0.0, 0.0, 0.0); glShadeModel(GL_FLAT);
rect.xmin = 100; rect.xmax = 300; rect.ymin = 100; rect.ymax = 300;
x0 = 0; y0 = 360; x1 = 650; y1 = 0; }
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void Reshape(int w , int h ) {
glViewport(0, 0, (GLsizei ) w , (GLsizei ) h ); glMatrixMode(GL_PROJECTION); glLoadIdentity();
gluOrtho2D(0.0, (GLdouble ) w , 0.0, (GLdouble ) h ); }
//按键盘上字母c 裁剪，字母r 恢复原状，字母x 退出。 void keyboard(unsigned char key , int x , int y ) {
switch (key ) {
case "c" :
cohensutherlandlineclip(rect, x0, y0, x1, y1); glutPostRedisplay(); peak ; case "r" : Init();
glutPostRedisplay(); peak ; case "x" : exit(0); peak ; default : peak ; } }
int main(int argc , char * argv []) {
glutInit(&argc , argv );
glutInitDisplayMode(GLUT_RGB | GLUT_SINGLE); glutInitWindowPosition(100, 100); glutInitWindowSize(640, 480); glutCreateWindow(" 裁剪" );
Init();
glutDisplayFunc(myDisplay); glutReshapeFunc(Reshape); glutKeyboardFunc(keyboard); glutMainLoop(); return 0;
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