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Annotation of researchv10no/libplot/libpen/parabola.c, revision 1.1.1.1

1.1       root        1: #include "pen.h"
                      2: parabola(x0, y0, x1, y1, xb, yb)
                      3: double x0, y0, x1, y1, xb, yb;
                      4: {
                      5:        register double t, x, y;
                      6:        double d1, d2, dt;
                      7:        double c0x,c0y,c1x,c1y;
                      8:        if(noscale){
                      9:        x0 = SCX(x0);
                     10:        y0 = SCY(y0);
                     11:        x1 = SCX(x1);
                     12:        y1 = SCY(y1);
                     13:        xb = SCX(xb);
                     14:        yb = SCY(yb);
                     15:        }
                     16:        d1=sqrt((xb-x0)*(xb-x0)+(yb-y0)*(yb-y0));
                     17:        d2=sqrt((xb-x1)*(xb-x1)+(yb-y1)*(yb-y1));
                     18:        if (d1<=QUANTUM || d2<=QUANTUM) {
                     19:                penUp();
                     20:                fprintf(pltout,"PA %8.2f,%8.2f PD %8.2f,%8.2f",
                     21:                        x0,y0,x1,y1);
                     22:                penstate = DOWN;
                     23:        }
                     24:        else {
                     25:                c0x = x0 + x1 - 2.*xb; 
                     26:                c0y = y0 + y1 - 2.*yb; 
                     27:                c1x = 2. * (xb - x0);
                     28:                c1y = 2. * (yb - y0);
                     29:                penUp();
                     30:                fprintf(pltout,"PA %8.2f,%8.2f PD",x0,y0);      
                     31:                penstate = DOWN;
                     32:                dt = QUANTUM/d1;
                     33:                for (t=dt; t < 1.0; t += dt) {  
                     34:                        x = (c0x*t + c1x)*t + x0;
                     35:                        y = (c0y*t + c1y)*t + y0;
                     36:                        fprintf(pltout," %8.2f,%8.2f",x,y);
                     37:                }
                     38:                fprintf(pltout," %8.2f,%8.2f\n",x1,y1);
                     39:        }
                     40:        ckerr(0);
                     41: }

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