1*19975Sdist /* 2*19975Sdist * Copyright (c) 1980 Regents of the University of California. 3*19975Sdist * All rights reserved. The Berkeley software License Agreement 4*19975Sdist * specifies the terms and conditions for redistribution. 5*19975Sdist */ 6*19975Sdist 715445Sralph #ifndef lint 8*19975Sdist static char sccsid[] = "@(#)arc.c 5.1 (Berkeley) 05/07/85"; 9*19975Sdist #endif not lint 1015445Sralph 1115445Sralph #include "hp2648.h" 1215445Sralph 1315445Sralph arc(xcent,ycent,xbeg,ybeg,xend,yend) 1415445Sralph int xcent,ycent,xbeg,ybeg,xend,yend; 1515445Sralph { 1615445Sralph double costheta,sintheta,x,y,xn,r; 1715445Sralph double x1,y1,x2,y2; 1815445Sralph int xi,yi,crosspflag,crossp; 1915445Sralph 2015445Sralph r = (xcent-xbeg)*(xcent-xbeg)+(ycent-ybeg)*(ycent-ybeg); 2115445Sralph r = pow(r,0.5); 2215445Sralph if(r<1){ 2315445Sralph point(xcent,ycent); 2415445Sralph return; 2515445Sralph } 2615445Sralph sintheta = 1.0/r; 2715445Sralph costheta = pow(1-sintheta*sintheta,0.5); 2815445Sralph xi = x = xbeg-xcent; 2915445Sralph yi = y = ybeg-ycent; 3015445Sralph x1 = xcent; 3115445Sralph y1 = ycent; 3215445Sralph x2 = xend; 3315445Sralph y2 = yend; 3415445Sralph crosspflag = 0; 3515445Sralph do { 3615445Sralph crossp = cross_product(x1,y1,x2,y2,x,y); 3715445Sralph if(crossp >0 && crosspflag == 0) crosspflag = 1; 3815445Sralph point(xcent+xi,ycent+yi); 3915445Sralph xn = x; 4015445Sralph xi = x = x*costheta + y*sintheta; 4115445Sralph yi = y = y*costheta - xn*sintheta; 4215445Sralph } while( crosspflag == 0 || crossp >0); 4315445Sralph } 4415445Sralph 4515445Sralph cross_product(x1,y1,x2,y2,x3,y3) 4615445Sralph double x1,x2,x3,y1,y2,y3; 4715445Sralph { 4815445Sralph double z,a,b; 4915445Sralph a = (y3-y2)*(x2-x1); 5015445Sralph b = (x3-x2)*(y2-y1); 5115445Sralph z = a-b; 5215445Sralph if(z<0) return(-1); 5315445Sralph if(z>0) return(1); 5415445Sralph return(0); 5515445Sralph } 56