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>
33 fgFRAGMENT::fgFRAGMENT ( void ) {
37 // Add a face to the face list
38 void fgFRAGMENT::add_face(int n1, int n2, int n3) {
45 faces.push_back(face);
49 // return the sign of a value
50 static int fg_sign( double x ) {
59 // return the minimum of the three values
60 static double fg_min( double a, double b, double c ) {
63 if (result > b) result = b;
64 if (result > c) result = c;
70 // return the maximum of the three values
71 static double fg_max( double a, double b, double c ) {
74 if (result < b) result = b;
75 if (result < c) result = c;
81 // test if line intesects with this fragment. p0 and p1 are the two
82 // line end points of the line. If side_flag is true, check to see
83 // that end points are on opposite sides of face. Returns 1 if it
84 // does, 0 otherwise. If it intesects, result is the point of
87 int fgFRAGMENT::intersect( fgPoint3d *end0, fgPoint3d *end1, int side_flag,
92 MAT3vec v1, v2, n, center;
93 double p1[3], p2[3], p3[3];
95 double x0, y0, z0, x1, y1, z1, a1, b1, c1;
97 double xmin, xmax, ymin, ymax, zmin, zmax;
98 double dx, dy, dz, min_dim, x2, y2, x3, y3, rx, ry;
100 list < fgFACE > :: iterator current;
101 list < fgFACE > :: iterator last;
103 // find the associated tile
104 t = (fgTILE *)tile_ptr;
106 // printf("Intersecting\n");
108 // traverse the face list for this fragment
109 current = faces.begin();
111 while ( current != last ) {
117 // get face vertex coordinates
118 center[0] = t->center.x;
119 center[1] = t->center.y;
120 center[2] = t->center.z;
122 MAT3_ADD_VEC(p1, t->nodes[face.n1], center);
123 MAT3_ADD_VEC(p2, t->nodes[face.n2], center);
124 MAT3_ADD_VEC(p3, t->nodes[face.n3], center);
126 // printf("point 1 = %.2f %.2f %.2f\n", p1[0], p1[1], p1[2]);
127 // printf("point 2 = %.2f %.2f %.2f\n", p2[0], p2[1], p2[2]);
128 // printf("point 3 = %.2f %.2f %.2f\n", p3[0], p3[1], p3[2]);
130 // calculate two edge vectors, and the face normal
131 MAT3_SUB_VEC(v1, p2, p1);
132 MAT3_SUB_VEC(v2, p3, p1);
133 MAT3cross_product(n, v1, v2);
135 // calculate the plane coefficients for the plane defined by
136 // this face. If n is the normal vector, n = (a, b, c) and p1
137 // is a point on the plane, p1 = (x0, y0, z0), then the
138 // equation of the line is a(x-x0) + b(y-y0) + c(z-z0) = 0
142 d = a * p1[0] + b * p1[1] + c * p1[2];
143 // printf("a, b, c, d = %.2f %.2f %.2f %.2f\n", a, b, c, d);
145 // printf("p1(d) = %.2f\n", a * p1[0] + b * p1[1] + c * p1[2]);
146 // printf("p2(d) = %.2f\n", a * p2[0] + b * p2[1] + c * p2[2]);
147 // printf("p3(d) = %.2f\n", a * p3[0] + b * p3[1] + c * p3[2]);
149 // calculate the line coefficients for the specified line
150 x0 = end0->x; x1 = end1->x;
151 y0 = end0->y; y1 = end1->y;
152 z0 = end0->z; z1 = end1->z;
158 // intersect the specified line with this plane
162 // printf("a = %.2f t1 = %.2f t2 = %.2f\n", a, t1, t2);
164 if ( fabs(a + t1 + t2) > FG_EPSILON ) {
165 result->x = (t1*x0 - b*y0 + t2*x0 - c*z0 + d) / (a + t1 + t2);
166 result->y = (b1/a1) * (result->x - x0) + y0;
167 result->z = (c1/a1) * (result->x - x0) + z0;
168 // printf("result(d) = %.2f\n",
169 // a * result->x + b * result->y + c * result->z);
171 // no intersection point
176 // check to see if end0 and end1 are on opposite sides of
178 if ( (result->x - x0) > FG_EPSILON ) {
179 t1 = result->x; t2 = x0; t3 = x1;
180 } else if ( (result->y - y0) > FG_EPSILON ) {
181 t1 = result->y; t2 = y0; t3 = y1;
182 } else if ( (result->z - z0) > FG_EPSILON ) {
183 t1 = result->z; t2 = z0; t3 = z1;
185 // everything is too close together to tell the difference
186 // so the current intersection point should work as good
190 if ( fg_sign(t1 - t2) == fg_sign(t1 - t3) ) {
196 // check to see if intersection point is in the bounding
198 xmin = fg_min(p1[0], p2[0], p3[0]);
199 xmax = fg_max(p1[0], p2[0], p3[0]);
200 ymin = fg_min(p1[1], p2[1], p3[1]);
201 ymax = fg_max(p1[1], p2[1], p3[1]);
202 zmin = fg_min(p1[2], p2[2], p3[2]);
203 zmax = fg_max(p1[2], p2[2], p3[2]);
204 // printf("bounding cube = %.2f,%.2f,%.2f %.2f,%.2f,%.2f\n",
205 // xmin, ymin, zmin, xmax, ymax, zmax);
206 // punt if outside bouding cube
207 if ( result->x < xmin ) {
209 } else if ( result->x > xmax ) {
211 } else if ( result->y < ymin ) {
213 } else if ( result->y > ymax ) {
215 } else if ( result->z < zmin ) {
217 } else if ( result->z > zmax ) {
221 // (finally) check to see if the intersection point is
222 // actually inside this face
224 //first, drop the smallest dimension so we only have to work
229 min_dim = fg_min(dx, dy, dz);
230 if ( fabs(min_dim - dx) <= FG_EPSILON ) {
231 // x is the smallest dimension
232 x1 = p1[1]; y1 = p1[2];
233 x2 = p2[1]; y2 = p2[2];
234 x3 = p3[1]; y3 = p3[2];
235 rx = result->y; ry = result->z;
236 } else if ( fabs(min_dim - dy) <= FG_EPSILON ) {
237 // y is the smallest dimension
238 x1 = p1[0]; y1 = p1[2];
239 x2 = p2[0]; y2 = p2[2];
240 x3 = p3[0]; y3 = p3[2];
241 rx = result->x; ry = result->z;
242 } else if ( fabs(min_dim - dz) <= FG_EPSILON ) {
243 // z is the smallest dimension
244 x1 = p1[0]; y1 = p1[1];
245 x2 = p2[0]; y2 = p2[1];
246 x3 = p3[0]; y3 = p3[1];
247 rx = result->x; ry = result->y;
250 // check if intersection point is on the same side of p1 <-> p2 as p3
251 side1 = fg_sign((y1 - y2) * ((x3) - x2) / (x1 - x2) + y2 - (y3));
252 side2 = fg_sign((y1 - y2) * ((rx) - x2) / (x1 - x2) + y2 - (ry));
253 if ( side1 != side2 ) {
254 // printf("failed side 1 check\n");
258 // check if intersection point is on correct side of p2 <-> p3 as p1
259 side1 = fg_sign((y2 - y3) * ((x1) - x3) / (x2 - x3) + y3 - (y1));
260 side2 = fg_sign((y2 - y3) * ((rx) - x3) / (x2 - x3) + y3 - (ry));
261 if ( side1 != side2 ) {
262 // printf("failed side 2 check\n");
266 // check if intersection point is on correct side of p1 <-> p3 as p2
267 side1 = fg_sign((y1 - y3) * ((x2) - x3) / (x1 - x3) + y3 - (y2));
268 side2 = fg_sign((y1 - y3) * ((rx) - x3) / (x1 - x3) + y3 - (ry));
269 if ( side1 != side2 ) {
270 // printf("failed side 3 check\n");
274 // printf( "intersection point = %.2f %.2f %.2f\n",
275 // result->x, result->y, result->z);
286 fgFRAGMENT::~fgFRAGMENT ( void ) {
287 // Step through the face list deleting the items until the list is
290 // printf("destructing a fragment with %d faces\n", faces.size());
292 while ( faces.size() ) {
293 // printf("emptying face list\n");
300 fgTILE::fgTILE ( void ) {
301 nodes = new double[MAX_NODES][3];
306 fgTILE::~fgTILE ( void ) {
312 // Revision 1.2 1998/07/12 03:18:28 curt
313 // Added ground collision detection. This involved:
314 // - saving the entire vertex list for each tile with the tile records.
315 // - saving the face list for each fragment with the fragment records.
316 // - code to intersect the current vertical line with the proper face in
317 // an efficient manner as possible.
318 // Fixed a bug where the tiles weren't being shifted to "near" (0,0,0)
320 // Revision 1.1 1998/05/23 14:09:21 curt
321 // Added tile.cxx and tile.hxx.
322 // Working on rewriting the tile management system so a tile is just a list
323 // fragments, and the fragment record contains the display list for that fragment.