reactos/dll/glu32/libtess/geom.c

   1 /*
   2 ** License Applicability. Except to the extent portions of this file are
   3 ** made subject to an alternative license as permitted in the SGI Free
   4 ** Software License B, Version 1.1 (the "License"), the contents of this
   5 ** file are subject only to the provisions of the License. You may not use
   6 ** this file except in compliance with the License. You may obtain a copy
   7 ** of the License at Silicon Graphics, Inc., attn: Legal Services, 1600
   8 ** Amphitheatre Parkway, Mountain View, CA 94043-1351, or at:
   9 **
  10 ** http://oss.sgi.com/projects/FreeB
  11 **
  12 ** Note that, as provided in the License, the Software is distributed on an
  13 ** "AS IS" basis, with ALL EXPRESS AND IMPLIED WARRANTIES AND CONDITIONS
  14 ** DISCLAIMED, INCLUDING, WITHOUT LIMITATION, ANY IMPLIED WARRANTIES AND
  15 ** CONDITIONS OF MERCHANTABILITY, SATISFACTORY QUALITY, FITNESS FOR A
  16 ** PARTICULAR PURPOSE, AND NON-INFRINGEMENT.
  17 **
  18 ** Original Code. The Original Code is: OpenGL Sample Implementation,
  19 ** Version 1.2.1, released January 26, 2000, developed by Silicon Graphics,
  20 ** Inc. The Original Code is Copyright (c) 1991-2000 Silicon Graphics, Inc.
  21 ** Copyright in any portions created by third parties is as indicated
  22 ** elsewhere herein. All Rights Reserved.
  23 **
  24 ** Additional Notice Provisions: The application programming interfaces
  25 ** established by SGI in conjunction with the Original Code are The
  26 ** OpenGL(R) Graphics System: A Specification (Version 1.2.1), released
  27 ** April 1, 1999; The OpenGL(R) Graphics System Utility Library (Version
  28 ** 1.3), released November 4, 1998; and OpenGL(R) Graphics with the X
  29 ** Window System(R) (Version 1.3), released October 19, 1998. This software
  30 ** was created using the OpenGL(R) version 1.2.1 Sample Implementation
  31 ** published by SGI, but has not been independently verified as being
  32 ** compliant with the OpenGL(R) version 1.2.1 Specification.
  33 **
  34 */
  35 /*
  36 ** Author: Eric Veach, July 1994.
  37 **
  38 ** $Date$ $Revision: 1.1 $
  39 ** $Header: /cygdrive/c/RCVS/CVS/ReactOS/reactos/lib/glu32/libtess/geom.c,v 1.1 2004/02/02 16:39:15 navaraf Exp $
  40 */
  41
  42 #include "gluos.h"
  43 #include <assert.h>
  44 #include "mesh.h"
  45 #include "geom.h"
  46
  47 int __gl_vertLeq( GLUvertex *u, GLUvertex *v )
  48 {
  49   /* Returns TRUE if u is lexicographically <= v. */
  50
  51   return VertLeq( u, v );
  52 }
  53
  54 GLdouble __gl_edgeEval( GLUvertex *u, GLUvertex *v, GLUvertex *w )
  55 {
  56   /* Given three vertices u,v,w such that VertLeq(u,v) && VertLeq(v,w),
  57    * evaluates the t-coord of the edge uw at the s-coord of the vertex v.
  58    * Returns v->t - (uw)(v->s), ie. the signed distance from uw to v.
  59    * If uw is vertical (and thus passes thru v), the result is zero.
  60    *
  61    * The calculation is extremely accurate and stable, even when v
  62    * is very close to u or w.  In particular if we set v->t = 0 and
  63    * let r be the negated result (this evaluates (uw)(v->s)), then
  64    * r is guaranteed to satisfy MIN(u->t,w->t) <= r <= MAX(u->t,w->t).
  65    */
  66   GLdouble gapL, gapR;
  67
  68   assert( VertLeq( u, v ) && VertLeq( v, w ));
  69
  70   gapL = v->s - u->s;
  71   gapR = w->s - v->s;
  72
  73   if( gapL + gapR > 0 ) {
  74     if( gapL < gapR ) {
  75       return (v->t - u->t) + (u->t - w->t) * (gapL / (gapL + gapR));
  76     } else {
  77       return (v->t - w->t) + (w->t - u->t) * (gapR / (gapL + gapR));
  78     }
  79   }
  80   /* vertical line */
  81   return 0;
  82 }
  83
  84 GLdouble __gl_edgeSign( GLUvertex *u, GLUvertex *v, GLUvertex *w )
  85 {
  86   /* Returns a number whose sign matches EdgeEval(u,v,w) but which
  87    * is cheaper to evaluate.  Returns > 0, == 0 , or < 0
  88    * as v is above, on, or below the edge uw.
  89    */
  90   GLdouble gapL, gapR;
  91
  92   assert( VertLeq( u, v ) && VertLeq( v, w ));
  93
  94   gapL = v->s - u->s;
  95   gapR = w->s - v->s;
  96
  97   if( gapL + gapR > 0 ) {
  98     return (v->t - w->t) * gapL + (v->t - u->t) * gapR;
  99   }
 100   /* vertical line */
 101   return 0;
 102 }
 103
 104
 105 /***********************************************************************
 106  * Define versions of EdgeSign, EdgeEval with s and t transposed.
 107  */
 108
 109 GLdouble __gl_transEval( GLUvertex *u, GLUvertex *v, GLUvertex *w )
 110 {
 111   /* Given three vertices u,v,w such that TransLeq(u,v) && TransLeq(v,w),
 112    * evaluates the t-coord of the edge uw at the s-coord of the vertex v.
 113    * Returns v->s - (uw)(v->t), ie. the signed distance from uw to v.
 114    * If uw is vertical (and thus passes thru v), the result is zero.
 115    *
 116    * The calculation is extremely accurate and stable, even when v
 117    * is very close to u or w.  In particular if we set v->s = 0 and
 118    * let r be the negated result (this evaluates (uw)(v->t)), then
 119    * r is guaranteed to satisfy MIN(u->s,w->s) <= r <= MAX(u->s,w->s).
 120    */
 121   GLdouble gapL, gapR;
 122
 123   assert( TransLeq( u, v ) && TransLeq( v, w ));
 124
 125   gapL = v->t - u->t;
 126   gapR = w->t - v->t;
 127
 128   if( gapL + gapR > 0 ) {
 129     if( gapL < gapR ) {
 130       return (v->s - u->s) + (u->s - w->s) * (gapL / (gapL + gapR));
 131     } else {
 132       return (v->s - w->s) + (w->s - u->s) * (gapR / (gapL + gapR));
 133     }
 134   }
 135   /* vertical line */
 136   return 0;
 137 }
 138
 139 GLdouble __gl_transSign( GLUvertex *u, GLUvertex *v, GLUvertex *w )
 140 {
 141   /* Returns a number whose sign matches TransEval(u,v,w) but which
 142    * is cheaper to evaluate.  Returns > 0, == 0 , or < 0
 143    * as v is above, on, or below the edge uw.
 144    */
 145   GLdouble gapL, gapR;
 146
 147   assert( TransLeq( u, v ) && TransLeq( v, w ));
 148
 149   gapL = v->t - u->t;
 150   gapR = w->t - v->t;
 151
 152   if( gapL + gapR > 0 ) {
 153     return (v->s - w->s) * gapL + (v->s - u->s) * gapR;
 154   }
 155   /* vertical line */
 156   return 0;
 157 }
 158
 159
 160 int __gl_vertCCW( GLUvertex *u, GLUvertex *v, GLUvertex *w )
 161 {
 162   /* For almost-degenerate situations, the results are not reliable.
 163    * Unless the floating-point arithmetic can be performed without
 164    * rounding errors, *any* implementation will give incorrect results
 165    * on some degenerate inputs, so the client must have some way to
 166    * handle this situation.
 167    */
 168   return (u->s*(v->t - w->t) + v->s*(w->t - u->t) + w->s*(u->t - v->t)) >= 0;
 169 }
 170
 171 /* Given parameters a,x,b,y returns the value (b*x+a*y)/(a+b),
 172  * or (x+y)/2 if a==b==0.  It requires that a,b >= 0, and enforces
 173  * this in the rare case that one argument is slightly negative.
 174  * The implementation is extremely stable numerically.
 175  * In particular it guarantees that the result r satisfies
 176  * MIN(x,y) <= r <= MAX(x,y), and the results are very accurate
 177  * even when a and b differ greatly in magnitude.
 178  */
 179 #define RealInterpolate(a,x,b,y)                        \
 180   (a = (a < 0) ? 0 : a, b = (b < 0) ? 0 : b,            \
 181   ((a <= b) ? ((b == 0) ? ((x+y) / 2)                   \
 182                         : (x + (y-x) * (a/(a+b))))      \
 183             : (y + (x-y) * (b/(a+b)))))
 184
 185 #ifndef FOR_TRITE_TEST_PROGRAM
 186 #define Interpolate(a,x,b,y)    RealInterpolate(a,x,b,y)
 187 #else
 188
 189 /* Claim: the ONLY property the sweep algorithm relies on is that
 190  * MIN(x,y) <= r <= MAX(x,y).  This is a nasty way to test that.
 191  */
 192 #include <stdlib.h>
 193 extern int RandomInterpolate;
 194
 195 GLdouble Interpolate( GLdouble a, GLdouble x, GLdouble b, GLdouble y)
 196 {
 197 printf("*********************%d\n",RandomInterpolate);
 198   if( RandomInterpolate ) {
 199     a = 1.2 * drand48() - 0.1;
 200     a = (a < 0) ? 0 : ((a > 1) ? 1 : a);
 201     b = 1.0 - a;
 202   }
 203   return RealInterpolate(a,x,b,y);
 204 }
 205
 206 #endif
 207
 208 #define Swap(a,b)       if (1) { GLUvertex *t = a; a = b; b = t; } else
 209
 210 void __gl_edgeIntersect( GLUvertex *o1, GLUvertex *d1,
 211                          GLUvertex *o2, GLUvertex *d2,
 212                          GLUvertex *v )
 213 /* Given edges (o1,d1) and (o2,d2), compute their point of intersection.
 214  * The computed point is guaranteed to lie in the intersection of the
 215  * bounding rectangles defined by each edge.
 216  */
 217 {
 218   GLdouble z1, z2;
 219
 220   /* This is certainly not the most efficient way to find the intersection
 221    * of two line segments, but it is very numerically stable.
 222    *
 223    * Strategy: find the two middle vertices in the VertLeq ordering,
 224    * and interpolate the intersection s-value from these.  Then repeat
 225    * using the TransLeq ordering to find the intersection t-value.
 226    */
 227
 228   if( ! VertLeq( o1, d1 )) { Swap( o1, d1 ); }
 229   if( ! VertLeq( o2, d2 )) { Swap( o2, d2 ); }
 230   if( ! VertLeq( o1, o2 )) { Swap( o1, o2 ); Swap( d1, d2 ); }
 231
 232   if( ! VertLeq( o2, d1 )) {
 233     /* Technically, no intersection -- do our best */
 234     v->s = (o2->s + d1->s) / 2;
 235   } else if( VertLeq( d1, d2 )) {
 236     /* Interpolate between o2 and d1 */
 237     z1 = EdgeEval( o1, o2, d1 );
 238     z2 = EdgeEval( o2, d1, d2 );
 239     if( z1+z2 < 0 ) { z1 = -z1; z2 = -z2; }
 240     v->s = Interpolate( z1, o2->s, z2, d1->s );
 241   } else {
 242     /* Interpolate between o2 and d2 */
 243     z1 = EdgeSign( o1, o2, d1 );
 244     z2 = -EdgeSign( o1, d2, d1 );
 245     if( z1+z2 < 0 ) { z1 = -z1; z2 = -z2; }
 246     v->s = Interpolate( z1, o2->s, z2, d2->s );
 247   }
 248
 249   /* Now repeat the process for t */
 250
 251   if( ! TransLeq( o1, d1 )) { Swap( o1, d1 ); }
 252   if( ! TransLeq( o2, d2 )) { Swap( o2, d2 ); }
 253   if( ! TransLeq( o1, o2 )) { Swap( o1, o2 ); Swap( d1, d2 ); }
 254
 255   if( ! TransLeq( o2, d1 )) {
 256     /* Technically, no intersection -- do our best */
 257     v->t = (o2->t + d1->t) / 2;
 258   } else if( TransLeq( d1, d2 )) {
 259     /* Interpolate between o2 and d1 */
 260     z1 = TransEval( o1, o2, d1 );
 261     z2 = TransEval( o2, d1, d2 );
 262     if( z1+z2 < 0 ) { z1 = -z1; z2 = -z2; }
 263     v->t = Interpolate( z1, o2->t, z2, d1->t );
 264   } else {
 265     /* Interpolate between o2 and d2 */
 266     z1 = TransSign( o1, o2, d1 );
 267     z2 = -TransSign( o1, d2, d1 );
 268     if( z1+z2 < 0 ) { z1 = -z1; z2 = -z2; }
 269     v->t = Interpolate( z1, o2->t, z2, d2->t );
 270   }
 271 }