1 // fragment.cxx -- routines to handle "atomic" display objects
3 // Written by Curtis Olson, started August 1998.
5 // Copyright (C) 1998 Curtis L. Olson - curt@me.umn.edu
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>
28 #include <Scenery/tile.hxx>
30 #include "fragment.hxx"
33 // return the sign of a value
34 #define FG_SIGN( x ) ((x) < 0 ? -1 : 1)
36 // return min or max of two values
37 #define FG_MIN(A,B) ((A) < (B) ? (A) : (B))
38 #define FG_MAX(A,B) ((A) > (B) ? (A) : (B))
50 fgFACE :: fgFACE( const fgFACE & image ) :
51 n1( image.n1), n2( image.n2), n3( image.n3)
55 bool fgFACE :: operator < (const fgFACE & rhs )
57 return ( n1 < rhs.n1 ? true : false);
60 bool fgFACE :: operator == (const fgFACE & rhs )
62 return ((n1 == rhs.n1) && (n2 == rhs.n2) && ( n3 == rhs.n3));
67 fgFRAGMENT::fgFRAGMENT ( void ) {
72 fgFRAGMENT :: fgFRAGMENT ( const fgFRAGMENT & rhs ) :
73 center ( rhs.center ),
74 bounding_radius( rhs.bounding_radius ),
75 material_ptr ( rhs.material_ptr ),
76 tile_ptr ( rhs.tile_ptr ),
77 display_list ( rhs.display_list ),
79 num_faces ( rhs.num_faces )
83 fgFRAGMENT & fgFRAGMENT :: operator = ( const fgFRAGMENT & rhs )
85 if(!(this == &rhs )) {
87 bounding_radius = rhs.bounding_radius;
88 material_ptr = rhs.material_ptr;
89 tile_ptr = rhs.tile_ptr;
90 // display_list = rhs.display_list;
97 // Add a face to the face list
98 void fgFRAGMENT::add_face(int n1, int n2, int n3) {
105 faces.push_back(face);
110 // return the minimum of the three values
111 static double fg_min3 (double a, double b, double c)
113 return (a > b ? FG_MIN (b, c) : FG_MIN (a, c));
117 // return the maximum of the three values
118 static double fg_max3 (double a, double b, double c)
120 return (a < b ? FG_MAX (b, c) : FG_MAX (a, c));
124 // test if line intesects with this fragment. p0 and p1 are the two
125 // line end points of the line. If side_flag is true, check to see
126 // that end points are on opposite sides of face. Returns 1 if it
127 // intersection found, 0 otherwise. If it intesects, result is the
128 // point of intersection
130 int fgFRAGMENT::intersect( fgPoint3d *end0, fgPoint3d *end1, int side_flag,
135 MAT3vec v1, v2, n, center;
136 double p1[3], p2[3], p3[3];
137 double x, y, z; // temporary holding spot for result
139 double x0, y0, z0, x1, y1, z1, a1, b1, c1;
141 double xmin, xmax, ymin, ymax, zmin, zmax;
142 double dx, dy, dz, min_dim, x2, y2, x3, y3, rx, ry;
144 list < fgFACE > :: iterator current;
145 list < fgFACE > :: iterator last;
147 // find the associated tile
150 // printf("Intersecting\n");
152 // traverse the face list for this fragment
153 current = faces.begin();
155 while ( current != last ) {
161 // get face vertex coordinates
162 center[0] = t->center.x;
163 center[1] = t->center.y;
164 center[2] = t->center.z;
166 MAT3_ADD_VEC(p1, t->nodes[face.n1], center);
167 MAT3_ADD_VEC(p2, t->nodes[face.n2], center);
168 MAT3_ADD_VEC(p3, t->nodes[face.n3], center);
170 // printf("point 1 = %.2f %.2f %.2f\n", p1[0], p1[1], p1[2]);
171 // printf("point 2 = %.2f %.2f %.2f\n", p2[0], p2[1], p2[2]);
172 // printf("point 3 = %.2f %.2f %.2f\n", p3[0], p3[1], p3[2]);
174 // calculate two edge vectors, and the face normal
175 MAT3_SUB_VEC(v1, p2, p1);
176 MAT3_SUB_VEC(v2, p3, p1);
177 MAT3cross_product(n, v1, v2);
179 // calculate the plane coefficients for the plane defined by
180 // this face. If n is the normal vector, n = (a, b, c) and p1
181 // is a point on the plane, p1 = (x0, y0, z0), then the
182 // equation of the line is a(x-x0) + b(y-y0) + c(z-z0) = 0
186 d = a * p1[0] + b * p1[1] + c * p1[2];
187 // printf("a, b, c, d = %.2f %.2f %.2f %.2f\n", a, b, c, d);
189 // printf("p1(d) = %.2f\n", a * p1[0] + b * p1[1] + c * p1[2]);
190 // printf("p2(d) = %.2f\n", a * p2[0] + b * p2[1] + c * p2[2]);
191 // printf("p3(d) = %.2f\n", a * p3[0] + b * p3[1] + c * p3[2]);
193 // calculate the line coefficients for the specified line
194 x0 = end0->x; x1 = end1->x;
195 y0 = end0->y; y1 = end1->y;
196 z0 = end0->z; z1 = end1->z;
198 if ( fabs(x1 - x0) > FG_EPSILON ) {
199 a1 = 1.0 / (x1 - x0);
201 // we got a big divide by zero problem here
207 // intersect the specified line with this plane
211 // printf("a = %.2f t1 = %.2f t2 = %.2f\n", a, t1, t2);
213 if ( fabs(a + t1 + t2) > FG_EPSILON ) {
214 x = (t1*x0 - b*y0 + t2*x0 - c*z0 + d) / (a + t1 + t2);
218 // printf("result(d) = %.2f\n", a * x + b * y + c * z);
220 // no intersection point
225 // check to see if end0 and end1 are on opposite sides of
227 if ( (x - x0) > FG_EPSILON ) {
231 } else if ( (y - y0) > FG_EPSILON ) {
235 } else if ( (z - z0) > FG_EPSILON ) {
240 // everything is too close together to tell the difference
241 // so the current intersection point should work as good
248 side1 = FG_SIGN (t1 - t2);
249 side2 = FG_SIGN (t1 - t3);
250 if ( side1 == side2 ) {
256 // check to see if intersection point is in the bounding
258 #ifdef XTRA_DEBUG_STUFF
259 xmin = fg_min3 (p1[0], p2[0], p3[0]);
260 xmax = fg_max3 (p1[0], p2[0], p3[0]);
261 ymin = fg_min3 (p1[1], p2[1], p3[1]);
262 ymax = fg_max3 (p1[1], p2[1], p3[1]);
263 zmin = fg_min3 (p1[2], p2[2], p3[2]);
264 zmax = fg_max3 (p1[2], p2[2], p3[2]);
265 printf("bounding cube = %.2f,%.2f,%.2f %.2f,%.2f,%.2f\n",
266 xmin, ymin, zmin, xmax, ymax, zmax);
268 // punt if outside bouding cube
269 if ( x < (xmin = fg_min3 (p1[0], p2[0], p3[0])) ) {
271 } else if ( x > (xmax = fg_max3 (p1[0], p2[0], p3[0])) ) {
273 } else if ( y < (ymin = fg_min3 (p1[1], p2[1], p3[1])) ) {
275 } else if ( y > (ymax = fg_max3 (p1[1], p2[1], p3[1])) ) {
277 } else if ( z < (zmin = fg_min3 (p1[2], p2[2], p3[2])) ) {
279 } else if ( z > (zmax = fg_max3 (p1[2], p2[2], p3[2])) ) {
283 // (finally) check to see if the intersection point is
284 // actually inside this face
286 //first, drop the smallest dimension so we only have to work
291 min_dim = fg_min3 (dx, dy, dz);
292 if ( fabs(min_dim - dx) <= FG_EPSILON ) {
293 // x is the smallest dimension
302 } else if ( fabs(min_dim - dy) <= FG_EPSILON ) {
303 // y is the smallest dimension
312 } else if ( fabs(min_dim - dz) <= FG_EPSILON ) {
313 // z is the smallest dimension
323 // all dimensions are really small so lets call it close
324 // enough and return a successful match
331 // check if intersection point is on the same side of p1 <-> p2 as p3
332 t1 = (y1 - y2) / (x1 - x2);
333 side1 = FG_SIGN (t1 * ((x3) - x2) + y2 - (y3));
334 side2 = FG_SIGN (t1 * ((rx) - x2) + y2 - (ry));
335 if ( side1 != side2 ) {
336 // printf("failed side 1 check\n");
340 // check if intersection point is on correct side of p2 <-> p3 as p1
341 t1 = (y2 - y3) / (x2 - x3);
342 side1 = FG_SIGN (t1 * ((x1) - x3) + y3 - (y1));
343 side2 = FG_SIGN (t1 * ((rx) - x3) + y3 - (ry));
344 if ( side1 != side2 ) {
345 // printf("failed side 2 check\n");
349 // check if intersection point is on correct side of p1 <-> p3 as p2
350 t1 = (y1 - y3) / (x1 - x3);
351 side1 = FG_SIGN (t1 * ((x2) - x3) + y3 - (y2));
352 side2 = FG_SIGN (t1 * ((rx) - x3) + y3 - (ry));
353 if ( side1 != side2 ) {
354 // printf("failed side 3 check\n");
358 // printf( "intersection point = %.2f %.2f %.2f\n", x, y, z);
372 fgFRAGMENT::~fgFRAGMENT ( void ) {
373 // Step through the face list deleting the items until the list is
376 // printf("destructing a fragment with %d faces\n", faces.size());
378 while ( faces.size() ) {
379 // printf("emptying face list\n");
386 bool fgFRAGMENT :: operator == ( const fgFRAGMENT & rhs)
388 if(( center.x - rhs.center.x ) < FG_EPSILON) {
389 if(( center.y - rhs.center.y) < FG_EPSILON) {
390 if(( center.z - rhs.center.z) < FG_EPSILON) {
398 // comparison operator
399 bool fgFRAGMENT :: operator < ( const fgFRAGMENT &rhs)
401 // This is completely arbitrary. It satisfies RW's STL implementation
403 return bounding_radius < rhs.bounding_radius;
408 // Revision 1.1 1998/08/25 16:51:23 curt
409 // Moved from ../Scenery