reactos/dll/glu32/libtess/normal.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 */
  39
  40 #include "gluos.h"
  41 #include "mesh.h"
  42 #include "tess.h"
  43 #include "normal.h"
  44 #include <math.h>
  45 #include <assert.h>
  46
  47 #define TRUE 1
  48 #define FALSE 0
  49
  50 #define Dot(u,v)        (u[0]*v[0] + u[1]*v[1] + u[2]*v[2])
  51
  52 #if 0
  53 static void Normalize( GLdouble v[3] )
  54 {
  55   GLdouble len = v[0]*v[0] + v[1]*v[1] + v[2]*v[2];
  56
  57   assert( len > 0 );
  58   len = sqrt( len );
  59   v[0] /= len;
  60   v[1] /= len;
  61   v[2] /= len;
  62 }
  63 #endif
  64
  65 #undef  ABS
  66 #define ABS(x)  ((x) < 0 ? -(x) : (x))
  67
  68 static int LongAxis( GLdouble v[3] )
  69 {
  70   int i = 0;
  71
  72   if( ABS(v[1]) > ABS(v[0]) ) { i = 1; }
  73   if( ABS(v[2]) > ABS(v[i]) ) { i = 2; }
  74   return i;
  75 }
  76
  77 static void ComputeNormal( GLUtesselator *tess, GLdouble norm[3] )
  78 {
  79   GLUvertex *v, *v1, *v2;
  80   GLdouble c, tLen2, maxLen2;
  81   GLdouble maxVal[3], minVal[3], d1[3], d2[3], tNorm[3];
  82   GLUvertex *maxVert[3], *minVert[3];
  83   GLUvertex *vHead = &tess->mesh->vHead;
  84   int i;
  85
  86   maxVal[0] = maxVal[1] = maxVal[2] = -2 * GLU_TESS_MAX_COORD;
  87   minVal[0] = minVal[1] = minVal[2] = 2 * GLU_TESS_MAX_COORD;
  88
  89   for( v = vHead->next; v != vHead; v = v->next ) {
  90     for( i = 0; i < 3; ++i ) {
  91       c = v->coords[i];
  92       if( c < minVal[i] ) { minVal[i] = c; minVert[i] = v; }
  93       if( c > maxVal[i] ) { maxVal[i] = c; maxVert[i] = v; }
  94     }
  95   }
  96
  97   /* Find two vertices separated by at least 1/sqrt(3) of the maximum
  98    * distance between any two vertices
  99    */
 100   i = 0;
 101   if( maxVal[1] - minVal[1] > maxVal[0] - minVal[0] ) { i = 1; }
 102   if( maxVal[2] - minVal[2] > maxVal[i] - minVal[i] ) { i = 2; }
 103   if( minVal[i] >= maxVal[i] ) {
 104     /* All vertices are the same -- normal doesn't matter */
 105     norm[0] = 0; norm[1] = 0; norm[2] = 1;
 106     return;
 107   }
 108
 109   /* Look for a third vertex which forms the triangle with maximum area
 110    * (Length of normal == twice the triangle area)
 111    */
 112   maxLen2 = 0;
 113   v1 = minVert[i];
 114   v2 = maxVert[i];
 115   d1[0] = v1->coords[0] - v2->coords[0];
 116   d1[1] = v1->coords[1] - v2->coords[1];
 117   d1[2] = v1->coords[2] - v2->coords[2];
 118   for( v = vHead->next; v != vHead; v = v->next ) {
 119     d2[0] = v->coords[0] - v2->coords[0];
 120     d2[1] = v->coords[1] - v2->coords[1];
 121     d2[2] = v->coords[2] - v2->coords[2];
 122     tNorm[0] = d1[1]*d2[2] - d1[2]*d2[1];
 123     tNorm[1] = d1[2]*d2[0] - d1[0]*d2[2];
 124     tNorm[2] = d1[0]*d2[1] - d1[1]*d2[0];
 125     tLen2 = tNorm[0]*tNorm[0] + tNorm[1]*tNorm[1] + tNorm[2]*tNorm[2];
 126     if( tLen2 > maxLen2 ) {
 127       maxLen2 = tLen2;
 128       norm[0] = tNorm[0];
 129       norm[1] = tNorm[1];
 130       norm[2] = tNorm[2];
 131     }
 132   }
 133
 134   if( maxLen2 <= 0 ) {
 135     /* All points lie on a single line -- any decent normal will do */
 136     norm[0] = norm[1] = norm[2] = 0;
 137     norm[LongAxis(d1)] = 1;
 138   }
 139 }
 140
 141
 142 static void CheckOrientation( GLUtesselator *tess )
 143 {
 144   GLdouble area;
 145   GLUface *f, *fHead = &tess->mesh->fHead;
 146   GLUvertex *v, *vHead = &tess->mesh->vHead;
 147   GLUhalfEdge *e;
 148
 149   /* When we compute the normal automatically, we choose the orientation
 150    * so that the the sum of the signed areas of all contours is non-negative.
 151    */
 152   area = 0;
 153   for( f = fHead->next; f != fHead; f = f->next ) {
 154     e = f->anEdge;
 155     if( e->winding <= 0 ) continue;
 156     do {
 157       area += (e->Org->s - e->Dst->s) * (e->Org->t + e->Dst->t);
 158       e = e->Lnext;
 159     } while( e != f->anEdge );
 160   }
 161   if( area < 0 ) {
 162     /* Reverse the orientation by flipping all the t-coordinates */
 163     for( v = vHead->next; v != vHead; v = v->next ) {
 164       v->t = - v->t;
 165     }
 166     tess->tUnit[0] = - tess->tUnit[0];
 167     tess->tUnit[1] = - tess->tUnit[1];
 168     tess->tUnit[2] = - tess->tUnit[2];
 169   }
 170 }
 171
 172 #ifdef FOR_TRITE_TEST_PROGRAM
 173 #include <stdlib.h>
 174 extern int RandomSweep;
 175 #define S_UNIT_X        (RandomSweep ? (2*drand48()-1) : 1.0)
 176 #define S_UNIT_Y        (RandomSweep ? (2*drand48()-1) : 0.0)
 177 #else
 178 #if defined(SLANTED_SWEEP)
 179 /* The "feature merging" is not intended to be complete.  There are
 180  * special cases where edges are nearly parallel to the sweep line
 181  * which are not implemented.  The algorithm should still behave
 182  * robustly (ie. produce a reasonable tesselation) in the presence
 183  * of such edges, however it may miss features which could have been
 184  * merged.  We could minimize this effect by choosing the sweep line
 185  * direction to be something unusual (ie. not parallel to one of the
 186  * coordinate axes).
 187  */
 188 #define S_UNIT_X        0.50941539564955385     /* Pre-normalized */
 189 #define S_UNIT_Y        0.86052074622010633
 190 #else
 191 #define S_UNIT_X        1.0
 192 #define S_UNIT_Y        0.0
 193 #endif
 194 #endif
 195
 196 /* Determine the polygon normal and project vertices onto the plane
 197  * of the polygon.
 198  */
 199 void __gl_projectPolygon( GLUtesselator *tess )
 200 {
 201   GLUvertex *v, *vHead = &tess->mesh->vHead;
 202   GLdouble norm[3];
 203   GLdouble *sUnit, *tUnit;
 204   int i, computedNormal = FALSE;
 205
 206   norm[0] = tess->normal[0];
 207   norm[1] = tess->normal[1];
 208   norm[2] = tess->normal[2];
 209   if( norm[0] == 0 && norm[1] == 0 && norm[2] == 0 ) {
 210     ComputeNormal( tess, norm );
 211     computedNormal = TRUE;
 212   }
 213   sUnit = tess->sUnit;
 214   tUnit = tess->tUnit;
 215   i = LongAxis( norm );
 216
 217 #if defined(FOR_TRITE_TEST_PROGRAM) || defined(TRUE_PROJECT)
 218   /* Choose the initial sUnit vector to be approximately perpendicular
 219    * to the normal.
 220    */
 221   Normalize( norm );
 222
 223   sUnit[i] = 0;
 224   sUnit[(i+1)%3] = S_UNIT_X;
 225   sUnit[(i+2)%3] = S_UNIT_Y;
 226
 227   /* Now make it exactly perpendicular */
 228   w = Dot( sUnit, norm );
 229   sUnit[0] -= w * norm[0];
 230   sUnit[1] -= w * norm[1];
 231   sUnit[2] -= w * norm[2];
 232   Normalize( sUnit );
 233
 234   /* Choose tUnit so that (sUnit,tUnit,norm) form a right-handed frame */
 235   tUnit[0] = norm[1]*sUnit[2] - norm[2]*sUnit[1];
 236   tUnit[1] = norm[2]*sUnit[0] - norm[0]*sUnit[2];
 237   tUnit[2] = norm[0]*sUnit[1] - norm[1]*sUnit[0];
 238   Normalize( tUnit );
 239 #else
 240   /* Project perpendicular to a coordinate axis -- better numerically */
 241   sUnit[i] = 0;
 242   sUnit[(i+1)%3] = S_UNIT_X;
 243   sUnit[(i+2)%3] = S_UNIT_Y;
 244
 245   tUnit[i] = 0;
 246   tUnit[(i+1)%3] = (norm[i] > 0) ? -S_UNIT_Y : S_UNIT_Y;
 247   tUnit[(i+2)%3] = (norm[i] > 0) ? S_UNIT_X : -S_UNIT_X;
 248 #endif
 249
 250   /* Project the vertices onto the sweep plane */
 251   for( v = vHead->next; v != vHead; v = v->next ) {
 252     v->s = Dot( v->coords, sUnit );
 253     v->t = Dot( v->coords, tUnit );
 254   }
 255   if( computedNormal ) {
 256     CheckOrientation( tess );
 257   }
 258 }