1 /**************************************************************************
2 * polar.c -- routines to deal with polar math and transformations
4 * Written by Curtis Olson, started June 1997.
6 * Copyright (C) 1997 Curtis L. Olson - curt@infoplane.com
8 * This program is free software; you can redistribute it and/or
9 * modify it under the terms of the GNU General Public License as
10 * published by the Free Software Foundation; either version 2 of the
11 * License, or (at your option) any later version.
13 * This program is distributed in the hope that it will be useful, but
14 * WITHOUT ANY WARRANTY; without even the implied warranty of
15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
16 * General Public License for more details.
18 * You should have received a copy of the GNU General Public License
19 * along with this program; if not, write to the Free Software
20 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
23 * (Log is kept at end of this file)
24 **************************************************************************/
30 #include <Include/fg_constants.h>
35 /* we can save these values between calls for efficiency */
36 static double st, ct, sp, cp;
39 /* Convert a polar coordinate to a cartesian coordinate. Lon and Lat
40 * must be specified in radians. The FG convention is for distances
41 * to be specified in meters */
42 struct fgCartesianPoint fgPolarToCart(double lon, double lat, double radius) {
43 struct fgCartesianPoint pnew;
45 pnew.x = cos(lon) * cos(lat) * radius;
46 pnew.y = sin(lon) * cos(lat) * radius;
47 pnew.z = sin(lat) * radius;
53 /* Precalculate as much as possible so we can do a batch of transforms
54 * through the same angles, will rotates a cartesian point about the
55 * center of the earth by Theta (longitude axis) and Phi (latitude
58 /* Here are the unoptimized transformation equations
60 x' = cos(Phi) * cos(Theta) * x + cos(Phi) * sin(Theta) * y +
62 y' = -sin(Theta) * x + cos(Theta) * y
63 z' = -sin(Phi) * sin(Theta) * y - sin(Phi) * cos(Theta) * x +
67 void fgRotateBatchInit(double Theta, double Phi) {
68 printf("Theta = %.3f, Phi = %.3f\n", Theta, Phi);
76 /* Rotates a cartesian point about the center of the earth by Theta
77 * (longitude axis) and Phi (latitude axis) */
78 struct fgCartesianPoint fgRotateCartesianPoint(struct fgCartesianPoint p) {
79 struct fgCartesianPoint p1, p2;
81 /* printf("start = %.3f %.3f %.3f\n", p.x, p.y, p.z); */
83 /* rotate about the z axis */
84 p1.x = ct * p.x - st * p.y;
85 p1.y = st * p.x + ct * p.y;
88 /* printf("step 1 = %.3f %.3f %.3f\n", p1.x, p1.y, p1.z); */
90 /* rotate new point about y axis */
91 p2.x = cp * p1.x + sp * p1.z;
93 p2.z = cp * p1.z - sp * p1.x;
95 /* printf("cp = %.5f, sp = %.5f\n", cp, sp); */
96 /* printf("(1) = %.5f, (2) = %.5f\n", cp * p1.z, sp * p1.x); */
98 /* printf("step 2 = %.3f %.3f %.3f\n", p2.x, p2.y, p2.z); */
105 /* Revision 1.2 1998/04/14 02:26:07 curt
106 /* Code reorganizations. Added a Lib/ directory for more general libraries.
108 * Revision 1.1 1998/04/08 23:21:12 curt
109 * Adopted Gnu automake/autoconf system.
111 * Revision 1.5 1998/01/27 00:48:00 curt
112 * Incorporated Paul Bleisch's <bleisch@chromatic.com> new debug message
113 * system and commandline/config file processing code.
115 * Revision 1.4 1998/01/19 19:27:12 curt
116 * Merged in make system changes from Bob Kuehne <rpk@sgi.com>
117 * This should simplify things tremendously.
119 * Revision 1.3 1997/12/15 23:54:54 curt
120 * Add xgl wrappers for debugging.
121 * Generate terrain normals on the fly.
123 * Revision 1.2 1997/07/31 22:52:27 curt
124 * Working on redoing internal coordinate systems & scenery transformations.
126 * Revision 1.1 1997/07/07 21:02:36 curt