fwd.zip_open

// Cohen-Suderland Line Clipping Algorithm with Window to viewport Mapping */ #include <stdio.h> #include <GL/glut.h> #define outcode int double xmin=50,ymin=50, xmax=100,ymax=100; // Window boundaries double xvmin=200,yvmin=200,xvmax=300,yvmax=300; // Viewport boundaries //bit codes for the right, left, top, & bottom const int RIGHT = 8; const int LEFT = 2; const int TOP = 4; const int BOTTOM = 1; //used to compute bit codes of a point outcode ComputeOutCode (double x, double y); //Cohen-Sutherland clipping algorithm clips a line from //P0 = (x0, y0) to P1 = (x1, y1) against a rectangle with //diagonal from (xmin, ymin) to (xmax, ymax). void CohenSutherlandLineClipAndDraw (double x0, double y0,double x1, double y1) { //Outcodes for P0, P1, and whatever point lies outside the clip rectangle outcode outcode0, outcode1, outcodeOut; bool accept = false, done = false; //compute outcodes outcode0 = ComputeOutCode (x0, y0); outcode1 = ComputeOutCode (x1, y1); do{ if (!(outcode0 | outcode1)) //logical or is 0 Trivially accept & exit { accept = true; done = true; } else if (outcode0 & outcode1) //logical and is not 0. Trivially reject and exit done = true; else { //failed both tests, so calculate the line segment to clip //from an outside point to an intersection with clip edge double x, y; //At least one endpoint is outside the clip rectangle; pick it. outcodeOut = outcode0? outcode0: outcode1; //Now find the intersection point; //use formulas y = y0 + slope * (x - x0), x = x0 + (1/slope)* (y - y0) if (outcodeOut & TOP) //point is above the clip rectangle { x = x0 + (x1 - x0) * (ymax - y0)/(y1 - y0); y = ymax; } else if (outcodeOut & BOTTOM) //point is below the clip rectangle { x = x0 + (x1 - x0) * (ymin - y0)/(y1 - y0); y = ymin; } else if (outcodeOut & RIGHT) //point is to the right of clip rectangle { y = y0 + (y1 - y0) * (xmax - x0)/(x1 - x0); x = xmax; } else //point is to the left of clip rectangle { y = y0 + (y1 - y0) * (xmin - x0)/(x1 - x0); x = xmin; } //Now we move outside point to intersection point to clip //and get ready for next pass. if (outcodeOut == outcode0) { x0 = x; y0 = y; outcode0 = ComputeOutCode (x0, y0); } else { x1 = x; y1 = y; outcode1 = ComputeOutCode (x1, y1); } } }while (!done); if (accept) { // Window to viewport mappings double sx=(xvmax-xvmin)/(xmax-xmin); // Scale parameters double sy=(yvmax-yvmin)/(ymax-ymin); double vx0=xvmin+(x0-xmin)*sx; double vy0=yvmin+(y0-ymin)*sy; double vx1=xvmin+(x1-xmin)*sx; double vy1=yvmin+(y1-ymin)*sy; //draw a red colored viewport glColor3f(1.0, 0.0, 0.0); glBegin(GL_LINE_LOOP); glVertex2f(xvmin, yvmin); glVertex2f(xvmax, yvmin); glVertex2f(xvmax, yvmax); glVertex2f(xvmin, yvmax); glEnd(); glColor3f(0.0,0.0,1.0); // draw blue colored clipped line glBegin(GL_LINES); glVertex2d (vx0, vy0); glVertex2d (vx1, vy1); glEnd(); } } //Compute the bit code for a point (x, y) using the clip rectangle //bounded diagonally by (xmin, ymin), and (xmax, ymax) outcode ComputeOutCode (double x, double y) { outcode code = 0; if (y > ymax) //above the clip window code |= TOP; else if (y < ymin) //below the clip window code |= BOTTOM; if (x > xmax) //to the right of clip window code |= RIGHT; else if (x < xmin) //to the left of clip window code |= LEFT; return code; } void display() { double x0=60,y0=20,x1=80,y1=120; glClear(GL_COLOR_BUFFER_BIT); //draw the line with red color glColor3f(1.0,0.0,0.0); //bres(120,20,340,250); glBegin(GL_LINES); glVertex2d (x0, y0); glVertex2d (x1, y1); glEnd(); //draw a blue colored window glColor3f(0.0, 0.0, 1.0); glBegin(GL_LINE_LOOP); glVertex2f(xmin, ymin); glVertex2f(xmax, ymin); glVertex2f(xmax, ymax); glVertex2f(xmin, ymax); glEnd(); CohenSutherlandLineClipAndDraw(x0,y0,x1,y1); glFlush(); } void myinit() { glClearColor(1.0,1.0,1.0,1.0); glColor3f(1.0,0.0,0.0); glPointSize(1.0); glMatrixMode(GL_PROJECTION); glLoadIdentity(); gluOrtho2D(0.0,499.0,0.0,499.0); } void main(int argc, char** argv) { //int x1, x2, y1, y2; //printf("Enter End points:"); //scanf("%d%d%d%d", &x1,&x2,&y1,&y2); glutInit(&argc,argv); glutInitDisplayMode(GLUT_SINGLE|GLUT_RGB); glutInitWindowSize(500,500); glutInitWindowPosition(0,0); glutCreateWindow("Cohen Suderland Line Clipping Algorithm"); glutDisplayFunc(display); myinit(); glutMainLoop(); }