flightgear/Tri2obj/tri2obj.c

/* tri2obj.c -- read in a .ele/.node file pair generated by the triangle 
 *              program and output a simple Wavefront .obj file.
 *
 * Written by Curtis Olson, started October 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 <stdio.h>
#include <string.h>

#include "tri2obj.h"

#include "../../Src/constants.h"
#include "../../Src/types.h"
#include "../../Src/Math/fg_geodesy.h"
#include "../../Src/Math/mat3.h"
#include "../../Src/Math/polar.h"


int nodecount, tricount;
struct fgCartesianPoint nodes[MAX_NODES];
int tris[MAX_TRIS][3];
int new_tris[MAX_TRIS][3];


/* convert a geodetic point lon(arcsec), lat(arcsec), elev(meter) to
 * a cartesian point */
struct fgCartesianPoint geod_to_cart(double geod[3]) {
    struct fgCartesianPoint p;
    double gc_lon, gc_lat, sl_radius;

    /* printf("A geodetic point is (%.2f, %.2f, %.2f)\n", 
	   geod[0], geod[1], geod[2]); */

    gc_lon = geod[0]*ARCSEC_TO_RAD;
    fgGeodToGeoc(geod[1]*ARCSEC_TO_RAD, geod[2], &sl_radius, &gc_lat);

    /* printf("A geocentric point is (%.2f, %.2f, %.2f)\n", gc_lon, 
	   gc_lat, sl_radius+geod[2]); */

    p = fgPolarToCart(gc_lon, gc_lat, sl_radius+geod[2]);
    
    /* printf("A cart point is (%.8f, %.8f, %.8f)\n", p.x, p.y, p.z); */

    return(p);
}


/* given three points defining a triangle, calculate the normal */
void calc_normal(struct fgCartesianPoint p1, struct fgCartesianPoint p2, 
		 struct fgCartesianPoint p3, double normal[3])
{
    double v1[3], v2[3];
    float temp;

    v1[0] = p2.x - p1.x; v1[1] = p2.y - p1.y; v1[2] = p2.z - p1.z;
    v2[0] = p3.x - p1.x; v2[1] = p3.y - p1.y; v2[2] = p3.z - p1.z;

    MAT3cross_product(normal, v1, v2);
    MAT3_NORMALIZE_VEC(normal,temp);

    /* printf("Normal = %.2f %.2f %.2f\n", normal[0], normal[1], normal[2]); */
}


/* return the index of all triangles containing the specified node */
void find_tris(int n, int *t1, int *t2, int *t3) {
    int i;

    *t1 = *t2 = *t3 = 0;

    i = 1;
    while ( i <= tricount ) {
        if ( (n == tris[i][0]) || (n == tris[i][1]) || (n == tris[i][2]) ) {
            if ( *t1 == 0 ) {
		*t1 = i;
            } else if ( *t2 == 0 ) {
		*t2 = i;
	    } else {
		*t3 = i;
	    }
        }
        i++;
    }
}


/* Initialize a new mesh structure */
void triload(char *basename) {
    char nodename[256], elename[256];
    double n[3];
    FILE *node, *ele;
    int dim, junk1, junk2;
    int i;

    strcpy(nodename, basename);
    strcat(nodename, ".node");
    strcpy(elename, basename);
    strcat(elename, ".ele");

    printf("Loading node file:  %s ...\n", nodename);
    if ( (node = fopen(nodename, "r")) == NULL ) {
	printf("Cannot open file '%s'\n", nodename);
	exit(-1);
    }

    fscanf(node, "%d %d %d %d", &nodecount, &dim, &junk1, &junk2);

    if ( nodecount > MAX_NODES - 1 ) {
	printf("Error, too many nodes, need to increase array size\n");
	exit(-1);
    } else {
	printf("    Expecting %d nodes\n", nodecount);
    }

    for ( i = 1; i <= nodecount; i++ ) {
	fscanf(node, "%d %lf %lf %lf %d\n", &junk1, 
	       &n[0], &n[1], &n[2], &junk2);
	/* printf("%d %.2f %.2f %.2f\n", junk1, n[0], n[1], n[2]); */
	nodes[i] = geod_to_cart(n);
	/* printf("%d %.2f %.2f %.2f\n", 
	       junk1, nodes[i].x, nodes[i].y, nodes[i].z); */
    }

    fclose(node);

    printf("Loading element file:  %s ...\n", elename);
    if ( (ele = fopen(elename, "r")) == NULL ) {
	printf("Cannot open file '%s'\n", elename);
	exit(-1);
    }

    fscanf(ele, "%d %d %d", &tricount, &junk1, &junk2);

    if ( tricount > MAX_TRIS - 1 ) {
	printf("Error, too many elements, need to increase array size\n");
	exit(-1);
    } else {
	printf("    Expecting %d elements\n", tricount);
    }

    for ( i = 1; i <= tricount; i++ ) {
	fscanf(ele, "%d %d %d %d\n", &junk1, 
	       &tris[i][0], &tris[i][1], &tris[i][2]);
	/* printf("%d %d %d %d\n", junk1, tris[i][0], tris[i][1], tris[i][2]);*/
    }

    fclose(ele);
}


/* dump in WaveFront .obj format */
void dump_obj(char *basename) {
    char objname[256];
    double n1[3], n2[3], n3[3];
    FILE *obj;
    int i, t1, t2, t3, count;

    strcpy(objname, basename);
    strcat(objname, ".obj");

    printf("Dumping to file:  %s ...\n", objname);

    obj = fopen(objname, "w");

    /* dump vertices */
    printf("  writing vertices\n");
    for ( i = 1; i <= nodecount; i++ ) {
	fprintf(obj, "v %.2f %.2f %.2f\n", 
		nodes[i].x, nodes[i].y, nodes[i].z);
    }

    printf("  calculating and writing normals\n");
    /* calculate and generate normals */
    for ( i = 1; i <= nodecount; i++ ) {
	find_tris(i, &t1, &t2, &t3);

	n1[0] = n1[1] = n1[2] = 0.0;
	n2[0] = n2[1] = n2[2] = 0.0;
	n3[0] = n3[1] = n3[3] = 0.0;

	count = 1;
	calc_normal(nodes[tris[t1][0]], nodes[tris[t1][1]], nodes[tris[t1][2]], 
		    n1);

	if ( t2 > 0 ) {
	    calc_normal(nodes[tris[t2][0]], nodes[tris[t2][1]], 
			nodes[tris[t2][2]], n2);
	    count = 2;
	}

	if ( t3 > 0 ) {
	    calc_normal(nodes[tris[t3][0]], nodes[tris[t3][1]],
			nodes[tris[t3][2]], n3);
	    count = 3;
	}

	fprintf(obj, "vn %.4f %.4f %.4f\n", 
		( n1[0] + n2[0] + n3[0] ) / (double)count,
		( n1[1] + n2[1] + n3[1] ) / (double)count,
		( n1[2] + n2[2] + n3[2] ) / (double)count );
    }

    /* dump faces */
    printf("  writing faces\n");
    for ( i = 1; i <= tricount; i++ ) {
	fprintf(obj, "f %d//%d %d//%d %d//%d\n", 
		tris[i][0], tris[i][0], 
		tris[i][1], tris[i][1], 
		tris[i][2], tris[i][2]);
    }

    fclose(obj);
}

int main(int argc, char **argv) {
    char basename[256];

    strcpy(basename, argv[1]);

    /* load the input data files */
    triload(basename);

    /* dump in WaveFront .obj format */
    dump_obj(basename);

    return(0);
}


/* $Log$
/* Revision 1.3  1997/11/15 18:05:05  curt
/* minor tweaks ...
/*
 * Revision 1.2  1997/11/14 00:29:13  curt
 * Transform scenery coordinates at this point in pipeline when scenery is
 * being translated to .obj format, not when it is being loaded into the end
 * renderer.  Precalculate normals for each node as average of the normals
 * of each containing polygon so Garoude shading is now supportable.
 *
 * Revision 1.1  1997/10/29 23:05:15  curt
 * Initial revision.
 *
 */