1 // tile.cxx -- routines to handle a scenery tile
3 // Written by Curtis Olson, started May 1998.
5 // Copyright (C) 1998 Curtis L. Olson - curt@infoplane.com
7 // This program is free software; you can redistribute it and/or
8 // modify it under the terms of the GNU General Public License as
9 // published by the Free Software Foundation; either version 2 of the
10 // License, or (at your option) any later version.
12 // This program is distributed in the hope that it will be useful, but
13 // WITHOUT ANY WARRANTY; without even the implied warranty of
14 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15 // General Public License for more details.
17 // You should have received a copy of the GNU General Public License
18 // along with this program; if not, write to the Free Software
19 // Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
22 // (Log is kept at end of this file)
25 #include <Include/fg_constants.h>
26 #include <Include/fg_types.h>
27 #include <Math/mat3.h>
32 // return the sign of a value
33 #define FG_SIGN( x ) ((x) >= 0 ? 1 : -1)
35 // return min or max of two values
36 #define FG_MIN(A,B) ((A) < (B) ? (A) : (B))
37 #define FG_MAX(A,B) ((A) > (B) ? (A) : (B))
41 fgFRAGMENT::fgFRAGMENT ( void ) {
45 // Add a face to the face list
46 void fgFRAGMENT::add_face(int n1, int n2, int n3) {
53 faces.push_back(face);
58 // return the sign of a value
59 static int fg_sign( double x ) {
68 // return the minimum of the three values
69 static double fg_min( double a, double b, double c ) {
72 if (result > b) result = b;
73 if (result > c) result = c;
79 // return the maximum of the three values
80 static double fg_max( double a, double b, double c ) {
83 if (result < b) result = b;
84 if (result < c) result = c;
91 // return the minimum of the three values
92 static double fg_min3 (double a, double b, double c)
94 return (a > b ? FG_MIN (b, c) : FG_MIN (a, c));
98 // return the maximum of the three values
99 static double fg_max3 (double a, double b, double c)
101 return (a < b ? FG_MAX (b, c) : FG_MAX (a, c));
105 // test if line intesects with this fragment. p0 and p1 are the two
106 // line end points of the line. If side_flag is true, check to see
107 // that end points are on opposite sides of face. Returns 1 if it
108 // does, 0 otherwise. If it intesects, result is the point of
111 int fgFRAGMENT::intersect( fgPoint3d *end0, fgPoint3d *end1, int side_flag,
116 MAT3vec v1, v2, n, center;
117 double p1[3], p2[3], p3[3];
119 double x0, y0, z0, x1, y1, z1, a1, b1, c1;
121 double xmin, xmax, ymin, ymax, zmin, zmax;
122 double dx, dy, dz, min_dim, x2, y2, x3, y3, rx, ry;
124 list < fgFACE > :: iterator current;
125 list < fgFACE > :: iterator last;
127 // find the associated tile
128 t = (fgTILE *)tile_ptr;
130 // printf("Intersecting\n");
132 // traverse the face list for this fragment
133 current = faces.begin();
135 while ( current != last ) {
141 // get face vertex coordinates
142 center[0] = t->center.x;
143 center[1] = t->center.y;
144 center[2] = t->center.z;
146 MAT3_ADD_VEC(p1, t->nodes[face.n1], center);
147 MAT3_ADD_VEC(p2, t->nodes[face.n2], center);
148 MAT3_ADD_VEC(p3, t->nodes[face.n3], center);
150 // printf("point 1 = %.2f %.2f %.2f\n", p1[0], p1[1], p1[2]);
151 // printf("point 2 = %.2f %.2f %.2f\n", p2[0], p2[1], p2[2]);
152 // printf("point 3 = %.2f %.2f %.2f\n", p3[0], p3[1], p3[2]);
154 // calculate two edge vectors, and the face normal
155 MAT3_SUB_VEC(v1, p2, p1);
156 MAT3_SUB_VEC(v2, p3, p1);
157 MAT3cross_product(n, v1, v2);
159 // calculate the plane coefficients for the plane defined by
160 // this face. If n is the normal vector, n = (a, b, c) and p1
161 // is a point on the plane, p1 = (x0, y0, z0), then the
162 // equation of the line is a(x-x0) + b(y-y0) + c(z-z0) = 0
166 d = a * p1[0] + b * p1[1] + c * p1[2];
167 // printf("a, b, c, d = %.2f %.2f %.2f %.2f\n", a, b, c, d);
169 // printf("p1(d) = %.2f\n", a * p1[0] + b * p1[1] + c * p1[2]);
170 // printf("p2(d) = %.2f\n", a * p2[0] + b * p2[1] + c * p2[2]);
171 // printf("p3(d) = %.2f\n", a * p3[0] + b * p3[1] + c * p3[2]);
173 // calculate the line coefficients for the specified line
174 x0 = end0->x; x1 = end1->x;
175 y0 = end0->y; y1 = end1->y;
176 z0 = end0->z; z1 = end1->z;
178 if ( fabs(x1 - x0) > FG_EPSILON ) {
179 a1 = 1.0 / (x1 - x0);
181 // we got a big divide by zero problem here
187 // intersect the specified line with this plane
191 // printf("a = %.2f t1 = %.2f t2 = %.2f\n", a, t1, t2);
193 if ( fabs(a + t1 + t2) > FG_EPSILON ) {
194 result->x = (t1*x0 - b*y0 + t2*x0 - c*z0 + d) / (a + t1 + t2);
195 t3 = a1 * (result->x - x0);
196 result->y = b1 * t3 + y0;
197 result->z = c1 * t3 + z0;
198 // printf("result(d) = %.2f\n",
199 // a * result->x + b * result->y + c * result->z);
201 // no intersection point
206 // check to see if end0 and end1 are on opposite sides of
208 if ( (result->x - x0) > FG_EPSILON ) {
209 t1 = result->x; t2 = x0; t3 = x1;
210 } else if ( (result->y - y0) > FG_EPSILON ) {
211 t1 = result->y; t2 = y0; t3 = y1;
212 } else if ( (result->z - z0) > FG_EPSILON ) {
213 t1 = result->z; t2 = z0; t3 = z1;
215 // everything is too close together to tell the difference
216 // so the current intersection point should work as good
220 side1 = FG_SIGN (t1 - t2);
221 side2 = FG_SIGN (t1 - t3);
222 if ( side1 == side2 ) {
228 // check to see if intersection point is in the bounding
230 xmin = fg_min3 (p1[0], p2[0], p3[0]);
231 xmax = fg_max3 (p1[0], p2[0], p3[0]);
232 ymin = fg_min3 (p1[1], p2[1], p3[1]);
233 ymax = fg_max3 (p1[1], p2[1], p3[1]);
234 zmin = fg_min3 (p1[2], p2[2], p3[2]);
235 zmax = fg_max3 (p1[2], p2[2], p3[2]);
236 // printf("bounding cube = %.2f,%.2f,%.2f %.2f,%.2f,%.2f\n",
237 // xmin, ymin, zmin, xmax, ymax, zmax);
238 // punt if outside bouding cube
239 if ( result->x < xmin ) {
241 } else if ( result->x > xmax ) {
243 } else if ( result->y < ymin ) {
245 } else if ( result->y > ymax ) {
247 } else if ( result->z < zmin ) {
249 } else if ( result->z > zmax ) {
253 // (finally) check to see if the intersection point is
254 // actually inside this face
256 //first, drop the smallest dimension so we only have to work
261 min_dim = fg_min3 (dx, dy, dz);
262 if ( fabs(min_dim - dx) <= FG_EPSILON ) {
263 // x is the smallest dimension
264 x1 = p1[1]; y1 = p1[2];
265 x2 = p2[1]; y2 = p2[2];
266 x3 = p3[1]; y3 = p3[2];
267 rx = result->y; ry = result->z;
268 } else if ( fabs(min_dim - dy) <= FG_EPSILON ) {
269 // y is the smallest dimension
270 x1 = p1[0]; y1 = p1[2];
271 x2 = p2[0]; y2 = p2[2];
272 x3 = p3[0]; y3 = p3[2];
273 rx = result->x; ry = result->z;
274 } else if ( fabs(min_dim - dz) <= FG_EPSILON ) {
275 // z is the smallest dimension
276 x1 = p1[0]; y1 = p1[1];
277 x2 = p2[0]; y2 = p2[1];
278 x3 = p3[0]; y3 = p3[1];
279 rx = result->x; ry = result->y;
281 // all dimensions are really small so lets call it close
282 // enough and return a successful match
286 // check if intersection point is on the same side of p1 <-> p2 as p3
287 side1 = FG_SIGN ((y1 - y2) * ((x3) - x2) / (x1 - x2) + y2 - (y3));
288 side2 = FG_SIGN ((y1 - y2) * ((rx) - x2) / (x1 - x2) + y2 - (ry));
289 if ( side1 != side2 ) {
290 // printf("failed side 1 check\n");
294 // check if intersection point is on correct side of p2 <-> p3 as p1
295 side1 = FG_SIGN ((y2 - y3) * ((x1) - x3) / (x2 - x3) + y3 - (y1));
296 side2 = FG_SIGN ((y2 - y3) * ((rx) - x3) / (x2 - x3) + y3 - (ry));
297 if ( side1 != side2 ) {
298 // printf("failed side 2 check\n");
302 // check if intersection point is on correct side of p1 <-> p3 as p2
303 side1 = FG_SIGN ((y1 - y3) * ((x2) - x3) / (x1 - x3) + y3 - (y2));
304 side2 = FG_SIGN ((y1 - y3) * ((rx) - x3) / (x1 - x3) + y3 - (ry));
305 if ( side1 != side2 ) {
306 // printf("failed side 3 check\n");
310 // printf( "intersection point = %.2f %.2f %.2f\n",
311 // result->x, result->y, result->z);
322 fgFRAGMENT::~fgFRAGMENT ( void ) {
323 // Step through the face list deleting the items until the list is
326 // printf("destructing a fragment with %d faces\n", faces.size());
328 while ( faces.size() ) {
329 // printf("emptying face list\n");
336 fgTILE::fgTILE ( void ) {
337 nodes = new double[MAX_NODES][3];
342 fgTILE::~fgTILE ( void ) {
348 // Revision 1.3 1998/07/16 17:34:24 curt
349 // Ground collision detection optimizations contributed by Norman Vine.
351 // Revision 1.2 1998/07/12 03:18:28 curt
352 // Added ground collision detection. This involved:
353 // - saving the entire vertex list for each tile with the tile records.
354 // - saving the face list for each fragment with the fragment records.
355 // - code to intersect the current vertical line with the proper face in
356 // an efficient manner as possible.
357 // Fixed a bug where the tiles weren't being shifted to "near" (0,0,0)
359 // Revision 1.1 1998/05/23 14:09:21 curt
360 // Added tile.cxx and tile.hxx.
361 // Working on rewriting the tile management system so a tile is just a list
362 // fragments, and the fragment record contains the display list for that fragment.