100 lines
3.1 KiB
C++
100 lines
3.1 KiB
C++
//
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// "$Id: fl_curve.cxx,v 1.4 1999/01/07 19:17:37 mike Exp $"
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//
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// Bezier curve functions for the Fast Light Tool Kit (FLTK).
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//
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// Copyright 1998-1999 by Bill Spitzak and others.
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//
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// This library is free software; you can redistribute it and/or
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// modify it under the terms of the GNU Library General Public
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// License as published by the Free Software Foundation; either
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// version 2 of the License, or (at your option) any later version.
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//
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// This library is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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// Library General Public License for more details.
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//
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// You should have received a copy of the GNU Library General Public
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// License along with this library; if not, write to the Free Software
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// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
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// USA.
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//
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// Please report all bugs and problems to "fltk-bugs@easysw.com".
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//
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// Utility for drawing Bezier curves, adding the points to
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// the current fl_begin/fl_vertex/fl_end path.
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// Incremental math implementation:
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// I very much doubt this is optimal! From Foley/vanDam page 511.
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// If anybody has a better algorithim, please send it!
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#include <FL/fl_draw.H>
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#include <math.h>
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void fl_curve(double X0, double Y0,
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double X1, double Y1,
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double X2, double Y2,
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double X3, double Y3) {
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double x = fl_transform_x(X0,Y0);
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double y = fl_transform_y(X0,Y0);
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double x1 = fl_transform_x(X1,Y1);
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double y1 = fl_transform_y(X1,Y1);
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double x2 = fl_transform_x(X2,Y2);
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double y2 = fl_transform_y(X2,Y2);
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double x3 = fl_transform_x(X3,Y3);
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double y3 = fl_transform_y(X3,Y3);
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int n; { // find smaller size of bounding box
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double lx = x; if (x1<lx) lx=x1; if (x2<lx) lx=x2; if (x3<lx) lx=x3;
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double rx = x; if (x1>rx) rx=x1; if (x2>rx) rx=x2; if (x3>rx) rx=x3;
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double ly = y; if (y1<ly) ly=y1; if (y2<ly) ly=y2; if (y3<ly) ly=y3;
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double ry = y; if (y1>ry) ry=y1; if (y2>ry) ry=y2; if (y3>ry) ry=y3;
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// calculate number of pieces to cut curve into:
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n = int((rx-lx+ry-ly)/8); if (n < 3) n = 3;
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}
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double e = 1.0/n;
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// calculate the coefficients of 3rd order equation:
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double xa = (x3-3*x2+3*x1-x);
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double xb = 3*(x2-2*x1+x);
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double xc = 3*(x1-x);
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// calculate the forward differences:
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double dx1 = ((xa*e+xb)*e+xc)*e;
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double dx3 = 6*xa*e*e*e;
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double dx2 = dx3 + 2*xb*e*e;
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// calculate the coefficients of 3rd order equation:
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double ya = (y3-3*y2+3*y1-y);
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double yb = 3*(y2-2*y1+y);
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double yc = 3*(y1-y);
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// calculate the forward differences:
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double dy1 = ((ya*e+yb)*e+yc)*e;
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double dy3 = 6*ya*e*e*e;
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double dy2 = dy3 + 2*yb*e*e;
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// draw point 0:
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fl_transformed_vertex(x,y);
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// draw points 1 .. n-2:
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for (int m=2; m<n; m++) {
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x += dx1;
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dx1 += dx2;
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dx2 += dx3;
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y += dy1;
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dy1 += dy2;
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dy2 += dy3;
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fl_transformed_vertex(x,y);
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}
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// draw point n-1:
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fl_transformed_vertex(x+dx1, y+dy1);
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// draw point n:
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fl_transformed_vertex(x3,y3);
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}
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//
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// End of "$Id: fl_curve.cxx,v 1.4 1999/01/07 19:17:37 mike Exp $".
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//
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