263 lines
7 KiB
C
263 lines
7 KiB
C
/**************************************************************************
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* mesh.c -- data structures and routines for processing terrain meshes
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*
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* Written by Curtis Olson, started May 1997.
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*
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* Copyright (C) 1997 Curtis L. Olson - curt@infoplane.com
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License as
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* published by the Free Software Foundation; either version 2 of the
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* License, or (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful, but
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* 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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* General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*
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* $Id$
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* (Log is kept at end of this file)
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**************************************************************************/
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#include <malloc.h>
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#include <stdio.h>
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#include <stdlib.h> /* atof(), atoi() */
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#include <string.h>
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#include <GL/glut.h>
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#include "mesh.h"
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#include "common.h"
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/* Temporary hack until we get the scenery management system running */
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extern GLint mesh_hack;
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extern struct mesh eg;
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/* initialize the non-array mesh values */
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void mesh_init(struct mesh *m) {
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m->originx = 0.0;
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m->originy = 0.0;
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m->rows = 0;
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m->cols = 0;
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m->row_step = 0.0;
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m->col_step = 0.0;
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m->cur_row = 0;
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m->cur_col = 0;
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m->do_data = 0;
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}
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/* return a pointer to a new mesh structure (no data array allocated yet) */
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struct mesh *(new_mesh)() {
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struct mesh *mesh_ptr;
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mesh_ptr = (struct mesh *)malloc(sizeof(struct mesh));
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if ( mesh_ptr == 0 ) {
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printf("Virtual memory exceeded\n");
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exit(-1);
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}
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mesh_ptr->cur_row = 0;
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mesh_ptr->cur_col = 0;
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return(mesh_ptr);
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}
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/* return a pointer to a dynamically allocated array */
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float *(new_mesh_data)(int nrows, int ncols) {
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float *mesh_data_ptr;
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mesh_data_ptr = (float *)malloc(nrows * ncols * sizeof(float));
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if ( mesh_data_ptr == 0 ) {
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printf("Virtual memory exceeded\n");
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exit(-1);
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}
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printf("Allocated float(%d, %d)\n", nrows, ncols);
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return(mesh_data_ptr);
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}
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/* set the option name in the mesh data structure */
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void mesh_set_option_name(struct mesh *m, char *name) {
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if ( strlen(name) < MAX_IDENT_LEN ) {
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strcpy(m->option_name, name);
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} else {
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strncpy(m->option_name, name, MAX_IDENT_LEN - 1);
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m->option_name[MAX_IDENT_LEN - 1] = '\0';
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}
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if ( strcmp(m->option_name, "do_data") == 0 ) {
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m->do_data = 1;
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} else {
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m->do_data = 0;
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}
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}
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/* set an option value in the mesh data structure */
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void mesh_set_option_value(struct mesh *m, char *value) {
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/* printf("Setting %s to %s\n", m->option_name, value); */
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if ( m->do_data ) {
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/* mesh data is a pseudo 2d array */
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/* printf("Setting mesh_data[%d][%d] to %s\n", m->cur_row, m->cur_col,
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value); */
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m->mesh_data[m->cur_row * m->rows + m->cur_col] = atof(value);
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m->cur_col++;
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if ( m->cur_col >= m->cols ) {
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m->cur_col = 0;
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m->cur_row++;
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if ( m->cur_row > m->rows ) {
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m->do_data = 0;
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}
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}
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} else if ( strcmp(m->option_name, "origin_lon") == 0 ) {
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m->originx = atof(value);
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} else if ( strcmp(m->option_name, "origin_lat") == 0 ) {
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m->originy = atof(value);
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} else if ( strcmp(m->option_name, "rows") == 0 ) {
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m->rows = atoi(value);
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} else if ( strcmp(m->option_name, "cols") == 0 ) {
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m->cols = atoi(value);
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} else if ( strcmp(m->option_name, "row_step") == 0 ) {
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m->row_step = atof(value);
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} else if ( strcmp(m->option_name, "col_step") == 0 ) {
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m->col_step = atof(value);
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} else {
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printf("Unknown option %s with value %s, ignoring ...\n",
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m->option_name, value);
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}
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}
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/* do whatever needs to be done with the mesh now that it's been
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loaded, such as generating the OpenGL call list. */
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void mesh_do_it(struct mesh *m) {
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mesh_hack = mesh2GL(m);
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}
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/* return the current altitude based on mesh data. We should rewrite
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* this to interpolate exact values, but for now this is good enough */
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double mesh_altitude(double lon, double lat) {
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/* we expect incoming (lon,lat) to be in arcsec for now */
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double xlocal, ylocal, dx, dy;
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int x1, y1, z1, x2, y2, z2, x3, y3, z3;
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int xindex, yindex;
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double tmp1, tmp2, tmp3, tmp4, tmp5, tmp6, tmp7, tmp8, tmp9, tmp10;
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double a, b, c;
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/* determine if we are in the lower triangle or the upper triangle
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______
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| /|
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| / |
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| / |
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|/ |
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------
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then calculate our end points
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*/
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xlocal = ( lon - eg.originx ) / eg.col_step;
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ylocal = ( lat - eg.originy ) / eg.row_step;
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xindex = (int)xlocal;
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yindex = (int)ylocal;
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dx = xlocal - xindex;
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dy = ylocal - yindex;
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x1 = xindex;
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y1 = yindex;
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z1 = eg.mesh_data[x1 * eg.rows + y1];
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x2 = xindex + eg.col_step;
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y2 = yindex + eg.row_step;
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z2 = eg.mesh_data[x2 * eg.rows + y2];
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if ( dx > dy ) {
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x3 = xindex + eg.col_step;
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y3 = yindex;
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z3 = eg.mesh_data[x3 * eg.rows + y3];
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} else {
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x3 = xindex;
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y3 = yindex + eg.row_step;
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z3 = eg.mesh_data[x3 * eg.rows + y3];
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}
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/* given (x1, y1, z1) (x2, y2, z2) and (x3, y3, z3) calculate (a,
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* b, c) such that z = ax + by + c is the equation of the plane
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* intersecting the three given points */
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tmp1 = (x2 * z1 / x1 - z2);
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tmp2 = (y2 - x2 * y1 / x1);
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tmp3 = (x2 * y1 / x1 - y2);
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tmp4 = (1 - x2 / x1);
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tmp5 = (x3*(z1 + y1*tmp1 / tmp2) / x1 - z3 + y3*tmp1 / tmp3);
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tmp6 = x3*(y1*tmp4 / tmp2 - 1);
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tmp7 = tmp5 / (y3*tmp4 / tmp2 - tmp6 / x1 - 1);
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tmp8 = (tmp6 / x1 + y3*tmp4 / tmp3 + 1);
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tmp9 = (z1 + tmp5 / tmp8);
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tmp10 = (tmp7 + x2*tmp9 / x1 - z2);
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a = (tmp9 + y1*tmp10 / tmp2) / x1;
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b = tmp10 / tmp3;
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c = tmp7;
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/* Then, given a position we can calculate the current ground elevation */
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printf("Our true ground elevation is %.2f\n", a*lon + b*lat + c);
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if ( (xindex >= 0) && (xindex < eg.cols) ) {
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if ( (yindex >= 0) && (yindex < eg.rows) ) {
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return( eg.mesh_data[xindex * eg.rows + yindex] );
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}
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}
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}
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/* $Log$
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/* Revision 1.9 1997/07/10 02:22:10 curt
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/* Working on terrain elevation interpolation routine.
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/*
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* Revision 1.8 1997/07/09 21:31:15 curt
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* Working on making the ground "hard."
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*
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* Revision 1.7 1997/07/08 18:20:13 curt
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* Working on establishing a hard ground.
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*
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* Revision 1.6 1997/06/29 21:16:49 curt
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* More twiddling with the Scenery Management system.
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*
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* Revision 1.5 1997/06/22 21:44:41 curt
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* Working on intergrating the VRML (subset) parser.
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*
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* Revision 1.4 1997/05/30 19:30:17 curt
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* The LaRCsim flight model is starting to look like it is working.
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*
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* Revision 1.3 1997/05/23 15:40:41 curt
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* Added GNU copyright headers.
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*
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* Revision 1.2 1997/05/19 18:20:50 curt
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* Slight change to origin key words.
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*
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* Revision 1.1 1997/05/16 16:07:04 curt
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* Initial revision.
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*
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*/
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