1 /**************************************************************************
2 * mesh.c -- data structures and routines for processing terrain meshes
4 * Written by Curtis Olson, started May 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 **************************************************************************/
29 #include <stdlib.h> /* atof(), atoi() */
38 /* Temporary hack until we get the scenery management system running */
39 extern GLint mesh_hack;
40 extern struct mesh eg;
42 /* initialize the non-array mesh values */
43 void mesh_init(struct mesh *m) {
59 /* return a pointer to a new mesh structure (no data array allocated yet) */
60 struct mesh *(new_mesh)() {
61 struct mesh *mesh_ptr;
63 mesh_ptr = (struct mesh *)malloc(sizeof(struct mesh));
65 if ( mesh_ptr == 0 ) {
66 printf("Virtual memory exceeded\n");
70 mesh_ptr->cur_row = 0;
71 mesh_ptr->cur_col = 0;
77 /* return a pointer to a dynamically allocated array */
78 float *(new_mesh_data)(int nrows, int ncols) {
81 mesh_data_ptr = (float *)malloc(nrows * ncols * sizeof(float));
83 if ( mesh_data_ptr == 0 ) {
84 printf("Virtual memory exceeded\n");
88 printf("Allocated float(%d, %d)\n", nrows, ncols);
90 return(mesh_data_ptr);
94 /* set the option name in the mesh data structure */
95 void mesh_set_option_name(struct mesh *m, char *name) {
96 if ( strlen(name) < MAX_IDENT_LEN ) {
97 strcpy(m->option_name, name);
99 strncpy(m->option_name, name, MAX_IDENT_LEN - 1);
100 m->option_name[MAX_IDENT_LEN - 1] = '\0';
102 if ( strcmp(m->option_name, "do_data") == 0 ) {
110 /* set an option value in the mesh data structure */
111 void mesh_set_option_value(struct mesh *m, char *value) {
112 /* printf("Setting %s to %s\n", m->option_name, value); */
115 /* mesh data is a pseudo 2d array */
116 /* printf("Setting mesh_data[%d][%d] to %s\n", m->cur_row, m->cur_col,
118 m->mesh_data[m->cur_row * m->rows + m->cur_col] = atof(value);
120 if ( m->cur_col >= m->cols ) {
123 if ( m->cur_row > m->rows ) {
127 } else if ( strcmp(m->option_name, "origin_lon") == 0 ) {
128 m->originx = atof(value);
129 } else if ( strcmp(m->option_name, "origin_lat") == 0 ) {
130 m->originy = atof(value);
131 } else if ( strcmp(m->option_name, "rows") == 0 ) {
132 m->rows = atoi(value);
133 } else if ( strcmp(m->option_name, "cols") == 0 ) {
134 m->cols = atoi(value);
135 } else if ( strcmp(m->option_name, "row_step") == 0 ) {
136 m->row_step = atof(value);
137 } else if ( strcmp(m->option_name, "col_step") == 0 ) {
138 m->col_step = atof(value);
140 printf("Unknown option %s with value %s, ignoring ...\n",
141 m->option_name, value);
146 /* do whatever needs to be done with the mesh now that it's been
147 loaded, such as generating the OpenGL call list. */
148 void mesh_do_it(struct mesh *m) {
149 mesh_hack = mesh2GL(m);
153 /* return the current altitude based on mesh data. We should rewrite
154 * this to interpolate exact values, but for now this is good enough */
155 double mesh_altitude(double lon, double lat) {
156 /* we expect incoming (lon,lat) to be in arcsec for now */
158 double xoffset, yoffset;
161 /* determine if we are in the lower triangle or the upper triangle
170 xoffset = lon - eg.originx;
171 yoffset = lat - eg.originy;
173 xindex = xoffset / eg.col_step;
174 yindex = yoffset / eg.row_step;
176 if ( xindex > yindex ) {
178 if ( (xindex >= 0) && (xindex < eg.cols) ) {
179 if ( (yindex >= 0) && (yindex < eg.rows) ) {
180 return( eg.mesh_data[xindex * eg.rows + yindex] );
185 given (x1, y1, z1) (x2, y2, z2) and (x3, y3, z3)
186 calculate z = ax + by + c (the equation of the plane intersecting the
189 Then, given a position we can calculate the current ground elevation
191 tmp1 = (x2 * z1 / x1 - z2);
192 tmp2 = (y2 - x2 * y1 / x1);
193 tmp3 = (x2 * y1 / x1 - y2);
194 tmp4 = (1 - x2 / x1);
195 tmp5 = (x3*(z1 + y1*tmp1 / tmp2) / x1 - z3 + y3*tmp1 / tmp3);
196 tmp6 = x3*(y1*tmp4 / tmp2 - 1);
197 tmp7 = tmp5 / (y3*tmp4 / tmp2 - tmp6 / x1 - 1);
198 tmp8 = (tmp6 / x1 + y3*tmp4 / tmp3 + 1);
199 tmp9 = (z1 + tmp5 / tmp8);
200 tmp10 = (tmp7 + x2*tmp9 / x1 - z2);
202 a = (tmp9 + y1*tmp10 / tmp2) / x1;
213 /* Revision 1.8 1997/07/09 21:31:15 curt
214 /* Working on making the ground "hard."
216 * Revision 1.7 1997/07/08 18:20:13 curt
217 * Working on establishing a hard ground.
219 * Revision 1.6 1997/06/29 21:16:49 curt
220 * More twiddling with the Scenery Management system.
222 * Revision 1.5 1997/06/22 21:44:41 curt
223 * Working on intergrating the VRML (subset) parser.
225 * Revision 1.4 1997/05/30 19:30:17 curt
226 * The LaRCsim flight model is starting to look like it is working.
228 * Revision 1.3 1997/05/23 15:40:41 curt
229 * Added GNU copyright headers.
231 * Revision 1.2 1997/05/19 18:20:50 curt
232 * Slight change to origin key words.
234 * Revision 1.1 1997/05/16 16:07:04 curt