src/glu/sgi/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 ** $Date: 2001/03/17 00:25:41 $ $Revision: 1.1 $
  39 ** $Header: /home/krh/git/sync/mesa-cvs-repo/Mesa/src/glu/sgi/libtess/normal.c,v 1.1 2001/03/17 00:25:41 brianp Exp $
  40 */
  41
  42 #include "gluos.h"
  43 #include "mesh.h"
  44 #include "tess.h"
  45 #include "normal.h"
  46 #include <math.h>
  47 #include <assert.h>
  48
  49 #define TRUE 1
  50 #define FALSE 0
  51
  52 #define Dot(u,v)        (u[0]*v[0] + u[1]*v[1] + u[2]*v[2])
  53
  54 static void Normalize( GLdouble v[3] )
  55 {
  56   GLdouble len = v[0]*v[0] + v[1]*v[1] + v[2]*v[2];
  57
  58   assert( len > 0 );
  59   len = sqrt( len );
  60   v[0] /= len;
  61   v[1] /= len;
  62   v[2] /= len;
  63 }
  64
  65 #define ABS(x)  ((x) < 0 ? -(x) : (x))
  66
  67 static int LongAxis( GLdouble v[3] )
  68 {
  69   int i = 0;
  70
  71   if( ABS(v[1]) > ABS(v[0]) ) { i = 1; }
  72   if( ABS(v[2]) > ABS(v[i]) ) { i = 2; }
  73   return i;
  74 }
  75
  76 static void ComputeNormal( GLUtesselator *tess, GLdouble norm[3] )
  77 {
  78   GLUvertex *v, *v1, *v2;
  79   GLdouble c, tLen2, maxLen2;
  80   GLdouble maxVal[3], minVal[3], d1[3], d2[3], tNorm[3];
  81   GLUvertex *maxVert[3], *minVert[3];
  82   GLUvertex *vHead = &tess->mesh->vHead;
  83   int i;
  84
  85   maxVal[0] = maxVal[1] = maxVal[2] = -2 * GLU_TESS_MAX_COORD;
  86   minVal[0] = minVal[1] = minVal[2] = 2 * GLU_TESS_MAX_COORD;
  87
  88   for( v = vHead->next; v != vHead; v = v->next ) {
  89     for( i = 0; i < 3; ++i ) {
  90       c = v->coords[i];
  91       if( c < minVal[i] ) { minVal[i] = c; minVert[i] = v; }
  92       if( c > maxVal[i] ) { maxVal[i] = c; maxVert[i] = v; }
  93     }
  94   }
  95
  96   /* Find two vertices separated by at least 1/sqrt(3) of the maximum
  97    * distance between any two vertices
  98    */
  99   i = 0;
 100   if( maxVal[1] - minVal[1] > maxVal[0] - minVal[0] ) { i = 1; }
 101   if( maxVal[2] - minVal[2] > maxVal[i] - minVal[i] ) { i = 2; }
 102   if( minVal[i] >= maxVal[i] ) {
 103     /* All vertices are the same -- normal doesn't matter */
 104     norm[0] = 0; norm[1] = 0; norm[2] = 1;
 105     return;
 106   }
 107
 108   /* Look for a third vertex which forms the triangle with maximum area
 109    * (Length of normal == twice the triangle area)
 110    */
 111   maxLen2 = 0;
 112   v1 = minVert[i];
 113   v2 = maxVert[i];
 114   d1[0] = v1->coords[0] - v2->coords[0];
 115   d1[1] = v1->coords[1] - v2->coords[1];
 116   d1[2] = v1->coords[2] - v2->coords[2];
 117   for( v = vHead->next; v != vHead; v = v->next ) {
 118     d2[0] = v->coords[0] - v2->coords[0];
 119     d2[1] = v->coords[1] - v2->coords[1];
 120     d2[2] = v->coords[2] - v2->coords[2];
 121     tNorm[0] = d1[1]*d2[2] - d1[2]*d2[1];
 122     tNorm[1] = d1[2]*d2[0] - d1[0]*d2[2];
 123     tNorm[2] = d1[0]*d2[1] - d1[1]*d2[0];
 124     tLen2 = tNorm[0]*tNorm[0] + tNorm[1]*tNorm[1] + tNorm[2]*tNorm[2];
 125     if( tLen2 > maxLen2 ) {
 126       maxLen2 = tLen2;
 127       norm[0] = tNorm[0];
 128       norm[1] = tNorm[1];
 129       norm[2] = tNorm[2];
 130     }
 131   }
 132
 133   if( maxLen2 <= 0 ) {
 134     /* All points lie on a single line -- any decent normal will do */
 135     norm[0] = norm[1] = norm[2] = 0;
 136     norm[LongAxis(d1)] = 1;
 137   }
 138 }
 139
 140
 141 static void CheckOrientation( GLUtesselator *tess )
 142 {
 143   GLdouble area;
 144   GLUface *f, *fHead = &tess->mesh->fHead;
 145   GLUvertex *v, *vHead = &tess->mesh->vHead;
 146   GLUhalfEdge *e;
 147
 148   /* When we compute the normal automatically, we choose the orientation
 149    * so that the the sum of the signed areas of all contours is non-negative.
 150    */
 151   area = 0;
 152   for( f = fHead->next; f != fHead; f = f->next ) {
 153     e = f->anEdge;
 154     if( e->winding <= 0 ) continue;
 155     do {
 156       area += (e->Org->s - e->Dst->s) * (e->Org->t + e->Dst->t);
 157       e = e->Lnext;
 158     } while( e != f->anEdge );
 159   }
 160   if( area < 0 ) {
 161     /* Reverse the orientation by flipping all the t-coordinates */
 162     for( v = vHead->next; v != vHead; v = v->next ) {
 163       v->t = - v->t;
 164     }
 165     tess->tUnit[0] = - tess->tUnit[0];
 166     tess->tUnit[1] = - tess->tUnit[1];
 167     tess->tUnit[2] = - tess->tUnit[2];
 168   }
 169 }
 170
 171 #ifdef FOR_TRITE_TEST_PROGRAM
 172 #include <stdlib.h>
 173 extern int RandomSweep;
 174 #define S_UNIT_X        (RandomSweep ? (2*drand48()-1) : 1.0)
 175 #define S_UNIT_Y        (RandomSweep ? (2*drand48()-1) : 0.0)
 176 #else
 177 #if defined(SLANTED_SWEEP)
 178 /* The "feature merging" is not intended to be complete.  There are
 179  * special cases where edges are nearly parallel to the sweep line
 180  * which are not implemented.  The algorithm should still behave
 181  * robustly (ie. produce a reasonable tesselation) in the presence
 182  * of such edges, however it may miss features which could have been
 183  * merged.  We could minimize this effect by choosing the sweep line
 184  * direction to be something unusual (ie. not parallel to one of the
 185  * coordinate axes).
 186  */
 187 #define S_UNIT_X        0.50941539564955385     /* Pre-normalized */
 188 #define S_UNIT_Y        0.86052074622010633
 189 #else
 190 #define S_UNIT_X        1.0
 191 #define S_UNIT_Y        0.0
 192 #endif
 193 #endif
 194
 195 /* Determine the polygon normal and project vertices onto the plane
 196  * of the polygon.
 197  */
 198 void __gl_projectPolygon( GLUtesselator *tess )
 199 {
 200   GLUvertex *v, *vHead = &tess->mesh->vHead;
 201   GLdouble w, norm[3];
 202   GLdouble *sUnit, *tUnit;
 203   int i, computedNormal = FALSE;
 204
 205   norm[0] = tess->normal[0];
 206   norm[1] = tess->normal[1];
 207   norm[2] = tess->normal[2];
 208   if( norm[0] == 0 && norm[1] == 0 && norm[2] == 0 ) {
 209     ComputeNormal( tess, norm );
 210     computedNormal = TRUE;
 211   }
 212   sUnit = tess->sUnit;
 213   tUnit = tess->tUnit;
 214   i = LongAxis( norm );
 215
 216 #if defined(FOR_TRITE_TEST_PROGRAM) || defined(TRUE_PROJECT)
 217   /* Choose the initial sUnit vector to be approximately perpendicular
 218    * to the normal.
 219    */
 220   Normalize( norm );
 221
 222   sUnit[i] = 0;
 223   sUnit[(i+1)%3] = S_UNIT_X;
 224   sUnit[(i+2)%3] = S_UNIT_Y;
 225
 226   /* Now make it exactly perpendicular */
 227   w = Dot( sUnit, norm );
 228   sUnit[0] -= w * norm[0];
 229   sUnit[1] -= w * norm[1];
 230   sUnit[2] -= w * norm[2];
 231   Normalize( sUnit );
 232
 233   /* Choose tUnit so that (sUnit,tUnit,norm) form a right-handed frame */
 234   tUnit[0] = norm[1]*sUnit[2] - norm[2]*sUnit[1];
 235   tUnit[1] = norm[2]*sUnit[0] - norm[0]*sUnit[2];
 236   tUnit[2] = norm[0]*sUnit[1] - norm[1]*sUnit[0];
 237   Normalize( tUnit );
 238 #else
 239   /* Project perpendicular to a coordinate axis -- better numerically */
 240   sUnit[i] = 0;
 241   sUnit[(i+1)%3] = S_UNIT_X;
 242   sUnit[(i+2)%3] = S_UNIT_Y;
 243
 244   tUnit[i] = 0;
 245   tUnit[(i+1)%3] = (norm[i] > 0) ? -S_UNIT_Y : S_UNIT_Y;
 246   tUnit[(i+2)%3] = (norm[i] > 0) ? S_UNIT_X : -S_UNIT_X;
 247 #endif
 248
 249   /* Project the vertices onto the sweep plane */
 250   for( v = vHead->next; v != vHead; v = v->next ) {
 251     v->s = Dot( v->coords, sUnit );
 252     v->t = Dot( v->coords, tUnit );
 253   }
 254   if( computedNormal ) {
 255     CheckOrientation( tess );
 256   }
 257 }