+/*****************************************************************************
+** This is part of the CTSim program
+** Copyright (C) 1983-2000 Kevin Rosenberg
+**
+** $Id: circle.cpp,v 1.1 2000/06/19 18:05:03 kevin Exp $
+** $Log: circle.cpp,v $
+** Revision 1.1 2000/06/19 18:05:03 kevin
+** initial cvs import
+**
+** Revision 1.1 2000/06/13 16:20:31 kevin
+** finished c++ conversions
+**
+** Revision 1.2 2000/05/24 22:49:01 kevin
+** Updated SGP: first function X-windows version
+**
+** Revision 1.1.1.1 2000/04/28 13:02:44 kevin
+** Initial CVS import for first public release
+**
+**
+**
+** This program is free software; you can redistribute it and/or modify
+** it under the terms of the GNU General Public License (version 2) as
+** published by the Free Software Foundation.
+**
+** This program is distributed in the hope that it will be useful,
+** but WITHOUT ANY WARRANTY; without even the implied warranty of
+** MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+** GNU General Public License for more details.
+**
+** You should have received a copy of the GNU General Public License
+** along with this program; if not, write to the Free Software
+** Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+******************************************************************************/
+
+/* FUNCTION
+ * sgp2_circle - draw circle of radius r at current center
+ */
+
+#include "math.h"
+#include "kmath.h"
+#include "sgp.h"
+
+void
+sgp2_draw_circle (const double r)
+{
+ sgp2_draw_arc (0.0, 7.0, r);
+}
+
+/*==============================================================*/
+/* draw arc around current center. pass angles and radius */
+/*==============================================================*/
+
+void
+sgp2_draw_arc (double start, double stop, const double r)
+{
+ double c, s, theta, angle;
+ float x, y, xp, yp;
+
+ if ((stop-start) > 2 * PI)
+ stop = start + 2 * PI;
+ if ((start-stop) > 2 * PI)
+ stop = start + 2 * PI;
+ while (start >= stop)
+ stop += 2*PI;
+
+ x = r * cos ((double) start);
+ y = r * sin ((double) start);
+ sgp2_move_rel (x, y); /* move from center to start of arc */
+
+ theta = 5 * PI / 180;
+ c = cos(theta);
+ s = sin(theta);
+
+ for (angle = start; angle < stop - theta; angle += theta) {
+ xp = c * x - s * y;
+ yp = s * x + c * y;
+ sgp2_line_rel (xp - x, yp - y);
+ x = xp; y = yp;
+ }
+
+ c = cos (stop - angle);
+ s = sin (stop - angle);
+ xp = c * x - s * y;
+ yp = s * x + c * y;
+ sgp2_line_rel (xp - x, yp - y);
+
+ x = r * cos ((double) stop);
+ y = r * sin ((double) stop);
+ sgp2_move_rel (-x, -y); /* move back to center of circle */
+}