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flightgear/Scenery/mesh.c
curt 1f718dcc8f We now can interpolated ground elevation for any position in the grid. We 
can use this to enforce a "hard" ground.  We still need to enforce some
bounds checking so that we don't try to lookup data points outside the
grid data set.
1997-07-10 04:26:36 +00:00

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/**************************************************************************
* mesh.c -- data structures and routines for processing terrain meshes
*
* Written by Curtis Olson, started May 1997.
*
* Copyright (C) 1997 Curtis L. Olson - curt@infoplane.com
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License as
* published by the Free Software Foundation; either version 2 of the
* License, or (at your option) any later version.
*
* 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., 675 Mass Ave, Cambridge, MA 02139, USA.
*
* $Id$
* (Log is kept at end of this file)
**************************************************************************/
#include <malloc.h>
#include <stdio.h>
#include <stdlib.h> /* atof(), atoi() */
#include <string.h>
#include <GL/glut.h>
#include "mesh.h"
#include "common.h"
/* Temporary hack until we get the scenery management system running */
extern GLint mesh_hack;
extern struct mesh eg;
/* initialize the non-array mesh values */
void mesh_init(struct mesh *m) {
m->originx = 0.0;
m->originy = 0.0;
m->rows = 0;
m->cols = 0;
m->row_step = 0.0;
m->col_step = 0.0;
m->cur_row = 0;
m->cur_col = 0;
m->do_data = 0;
}
/* return a pointer to a new mesh structure (no data array allocated yet) */
struct mesh *(new_mesh)() {
struct mesh *mesh_ptr;
mesh_ptr = (struct mesh *)malloc(sizeof(struct mesh));
if ( mesh_ptr == 0 ) {
printf("Virtual memory exceeded\n");
exit(-1);
}
mesh_ptr->cur_row = 0;
mesh_ptr->cur_col = 0;
return(mesh_ptr);
}
/* return a pointer to a dynamically allocated array */
float *(new_mesh_data)(int nrows, int ncols) {
float *mesh_data_ptr;
mesh_data_ptr = (float *)malloc(nrows * ncols * sizeof(float));
if ( mesh_data_ptr == 0 ) {
printf("Virtual memory exceeded\n");
exit(-1);
}
printf("Allocated float(%d, %d)\n", nrows, ncols);
return(mesh_data_ptr);
}
/* set the option name in the mesh data structure */
void mesh_set_option_name(struct mesh *m, char *name) {
if ( strlen(name) < MAX_IDENT_LEN ) {
strcpy(m->option_name, name);
} else {
strncpy(m->option_name, name, MAX_IDENT_LEN - 1);
m->option_name[MAX_IDENT_LEN - 1] = '\0';
}
if ( strcmp(m->option_name, "do_data") == 0 ) {
m->do_data = 1;
} else {
m->do_data = 0;
}
}
/* set an option value in the mesh data structure */
void mesh_set_option_value(struct mesh *m, char *value) {
/* printf("Setting %s to %s\n", m->option_name, value); */
if ( m->do_data ) {
/* mesh data is a pseudo 2d array */
/* printf("Setting mesh_data[%d][%d] to %s\n", m->cur_row, m->cur_col,
value); */
m->mesh_data[m->cur_row * m->rows + m->cur_col] = atof(value);
m->cur_col++;
if ( m->cur_col >= m->cols ) {
m->cur_col = 0;
m->cur_row++;
if ( m->cur_row > m->rows ) {
m->do_data = 0;
}
}
} else if ( strcmp(m->option_name, "origin_lon") == 0 ) {
m->originx = atof(value);
} else if ( strcmp(m->option_name, "origin_lat") == 0 ) {
m->originy = atof(value);
} else if ( strcmp(m->option_name, "rows") == 0 ) {
m->rows = atoi(value);
} else if ( strcmp(m->option_name, "cols") == 0 ) {
m->cols = atoi(value);
} else if ( strcmp(m->option_name, "row_step") == 0 ) {
m->row_step = atof(value);
} else if ( strcmp(m->option_name, "col_step") == 0 ) {
m->col_step = atof(value);
} else {
printf("Unknown option %s with value %s, ignoring ...\n",
m->option_name, value);
}
}
/* do whatever needs to be done with the mesh now that it's been
loaded, such as generating the OpenGL call list. */
void mesh_do_it(struct mesh *m) {
mesh_hack = mesh2GL(m);
}
/* return the current altitude based on mesh data. We should rewrite
* this to interpolate exact values, but for now this is good enough */
double mesh_altitude(double lon, double lat) {
/* we expect incoming (lon,lat) to be in arcsec for now */
double xlocal, ylocal, dx, dy, zA, zB, elev;
int x1, y1, z1, x2, y2, z2, x3, y3, z3;
int xindex, yindex;
/* determine if we are in the lower triangle or the upper triangle
______
| /|
| / |
| / |
|/ |
------
then calculate our end points
*/
xlocal = ( lon - eg.originx ) / eg.col_step;
ylocal = ( lat - eg.originy ) / eg.row_step;
xindex = (int)xlocal;
yindex = (int)ylocal;
dx = xlocal - xindex;
dy = ylocal - yindex;
if ( dx > dy ) {
/* lower triangle */
printf(" Lower triangle\n");
x1 = xindex;
y1 = yindex;
z1 = eg.mesh_data[x1 * eg.rows + y1];
x2 = xindex + eg.col_step;
y2 = yindex;
z2 = eg.mesh_data[x2 * eg.rows + y2];
x3 = xindex + eg.col_step;
y3 = yindex + eg.row_step;
z3 = eg.mesh_data[x3 * eg.rows + y3];
printf(" (x1,y1,z1) = (%d,%d,%d)\n", x1, y1, z1);
printf(" (x2,y2,z2) = (%d,%d,%d)\n", x2, y2, z2);
printf(" (x3,y3,z3) = (%d,%d,%d)\n", x3, y3, z3);
zA = dx * (z2 - z1) / eg.col_step + z1;
zB = dx * (z3 - z1) / eg.col_step + z1;
printf(" zA = %.2f zB = %.2f\n", zA, zB);
elev = dy * (zB - zA) * eg.col_step / (eg.row_step * dx) + zA;
} else {
/* upper triangle */
printf(" Upper triangle\n");
x1 = xindex;
y1 = yindex;
z1 = eg.mesh_data[x1 * eg.rows + y1];
x2 = xindex;
y2 = yindex + eg.row_step;
z2 = eg.mesh_data[x2 * eg.rows + y2];
x3 = xindex + eg.col_step;
y3 = yindex + eg.row_step;
z3 = eg.mesh_data[x3 * eg.rows + y3];
printf(" (x1,y1,z1) = (%d,%d,%d)\n", x1, y1, z1);
printf(" (x2,y2,z2) = (%d,%d,%d)\n", x2, y2, z2);
printf(" (x3,y3,z3) = (%d,%d,%d)\n", x3, y3, z3);
zA = dy * (z2 - z1) / eg.row_step + z1;
zB = dy * (z3 - z1) / eg.row_step + z1;
printf(" zA = %.2f zB = %.2f\n", zA, zB );
printf(" dx = %.2f xB - xA = %.2f\n", dx,
eg.col_step * dy / eg.row_step);
elev = dx * (zB - zA) * eg.row_step / (eg.col_step * dy) + zA;
}
printf("Our true ground elevation is %.2f\n", elev);
return(elev);
}
/* $Log$
/* Revision 1.10 1997/07/10 04:26:38 curt
/* We now can interpolated ground elevation for any position in the grid. We
/* can use this to enforce a "hard" ground. We still need to enforce some
/* bounds checking so that we don't try to lookup data points outside the
/* grid data set.
/*
* Revision 1.9 1997/07/10 02:22:10 curt
* Working on terrain elevation interpolation routine.
*
* Revision 1.8 1997/07/09 21:31:15 curt
* Working on making the ground "hard."
*
* Revision 1.7 1997/07/08 18:20:13 curt
* Working on establishing a hard ground.
*
* Revision 1.6 1997/06/29 21:16:49 curt
* More twiddling with the Scenery Management system.
*
* Revision 1.5 1997/06/22 21:44:41 curt
* Working on intergrating the VRML (subset) parser.
*
* Revision 1.4 1997/05/30 19:30:17 curt
* The LaRCsim flight model is starting to look like it is working.
*
* Revision 1.3 1997/05/23 15:40:41 curt
* Added GNU copyright headers.
*
* Revision 1.2 1997/05/19 18:20:50 curt
* Slight change to origin key words.
*
* Revision 1.1 1997/05/16 16:07:04 curt
* Initial revision.
*
*/
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