open-gl.rar_open

////////////////////////////////////////////////////////////////////////// // // COMPUTER GRAPHICS USING OpenGL (Third Edition) // // Case 3.2.cpp (Cohen-Sutherland) // // Written by Guangzheng Fei // Creation date: Wed. April. 6, 2011, 0:00 // // All Rights Reserved. // // Cohen-Sutherland 裁剪算法; ////////////////////////////////////////////////////////////////////////// #include <windows.h> #include <gl/GL.h> #include <gl/GLU.h> #include "glut.h" #include <cmath> #include <time.h> const double screenWidth = 640.0; const double screenHeight = 480.0; // GLintPoint typedef struct { GLint x, y; }GLintPoint; // RealRect typedef struct { GLint l, r, b, t; }RealRect; GLintPoint P1, P2; RealRect W; bool mode; ////////////////////////////////////setWindow///////////////////////////// void setWindow(GLdouble left, GLdouble right, GLdouble buttom, GLdouble top) { glMatrixMode(GL_PROJECTION); glLoadIdentity(); gluOrtho2D(left, right, buttom, top); } ////////////////////////////////////setViewport/////////////////////////// void setViewport(GLint left, GLint right, GLint bottom, GLint top) { glViewport(left, bottom, right - left, top - bottom); } ////////////////////////////////////myInit///////////////////////////////// void myInit(void) { glClear(GL_COLOR_BUFFER_BIT); glClearColor(1.0,1.0,1.0,0.0); glColor3f(0.0,0.0,0.0); glLineWidth(2.0); } ///////////////////////////////////setCode///////////////////////////////// void setCode(GLintPoint p, unsigned char &code) { code = 0; if(p.x<W.l) code|=8; if(p.y>W.t) code|=4; if(p.x>W.r) code|=2; if(p.y<W.b) code|=1; } ///////////////////////////////////ChopLine//////////////////////////////// void ChopLine(GLintPoint &p, unsigned char code, float dely, float delx) { if (code & 8)// 左边; { p.y+=(GLint)((W.l-p.x) * dely/delx); p.x = W.l; } else if (code & 2)// 右边; { p.y+=(GLint)((W.r-p.x) * dely/delx); p.x = W.r; } else if (code & 1)// 下边; { p.x+=(GLint)((W.b-p.y) * delx/dely); p.y = W.b; } else if (code & 4)// 上边; { p.x+=(GLint)((W.t-p.y) * delx/dely); p.y = W.t; } } ///////////////////////////////////clipSegment///////////////////////////// bool clipSegment(GLintPoint &p1, GLintPoint &p2) { unsigned char code1, code2; do { setCode(p1,code1); setCode(p2,code2); if (!(code1|code2)) return 1; // 完全可见 if (code1&code2) return 0; // 显然不可见 if (code1) ChopLine(p1,code1,(float)(p2.y-p1.y),(float)(p2.x-p1.x)); else ChopLine(p2,code2,(float)(p2.y-p1.y),(float)(p2.x-p1.x)); } while (1); } ///////////////////////////////////myDisplay/////////////////////////////// void myDisplay() { GLintPoint p1 = {(GLint)screenWidth/3, (GLint)screenHeight/3}, p2 = {(GLint)screenWidth*2/3, (GLint)screenHeight*2/3}; RealRect w = {p1.x, p2.x, p1.y, p2.y}; W = w; srand((unsigned int)time(0)); glClear(GL_COLOR_BUFFER_BIT); // 以下绘制一个矩形 glBegin(GL_LINE_LOOP); glVertex2i(W.l, W.b); glVertex2i(W.l, W.t); glVertex2i(W.r, W.t); glVertex2i(W.r, W.b); glEnd(); p1 = P1; p2 = P2; if (clipSegment(p1, p2)) // 裁剪后窗口内有可见部分 { glColor3f(1.0,0.0,0.0); glBegin(GL_LINES); // 先完整地绘制这条线段 glVertex2i(p1.x, p1.y); glVertex2i(p2.x, p2.y); glEnd(); glColor3f(0.0,0.0,0.0); glBegin(GL_LINES); // 再用覆盖的方式绘制两段不可见线段 glVertex2i(p1.x, p1.y); glVertex2i(P1.x, P1.y); glVertex2i(p2.x, p2.y); glVertex2i(P2.x, P2.y); glEnd(); } else // 线段完全不可见 { glBegin(GL_LINES); // 直接绘制这条原始线段 glVertex2i(P1.x, P1.y); glVertex2i(P2.x, P2.y); glEnd(); } glutSwapBuffers(); } ///////////////////////////////////myMouse//////////////////////////////// void myMouse(GLint button, GLint state, GLint x, GLint y) { if (button == GLUT_LEFT_BUTTON && state == GLUT_DOWN) { P1.x = x; P1.y = screenHeight - y; } if (button == GLUT_RIGHT_BUTTON && state == GLUT_DOWN) { mode = !mode; P2.x = x; P2.y = screenHeight - y; } glutPostRedisplay(); } ///////////////////////////////////myPassiveMouse///////////////////////// void myPassiveMouse(GLint x, GLint y) { if (mode) { P2.x = x; P2.y = screenHeight - y; glutPostRedisplay(); } } ///////////////////////////////////main/////////////////////////////////// void main(int argc, char** argv) { glutInit(&argc, argv); glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB); glutInitWindowSize((int)screenWidth,(int)screenHeight); glutInitWindowPosition(100,150); glutCreateWindow("Cohen-Sutherland"); setWindow(0.0,screenWidth,0.0,screenHeight);//必须在glutCreateWindow之后执行; myInit(); glutDisplayFunc(myDisplay); glutMouseFunc(myMouse); glutPassiveMotionFunc(myPassiveMouse); glutMainLoop(); }