src/glu/sgi/libnurbs/internals/monotonizer.cc

   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  * monotonizer.c++
  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/libnurbs/internals/monotonizer.cc,v 1.1 2001/03/17 00:25:41 brianp Exp $
  40  */
  41
  42 #include "glimports.h"
  43 #include "mystdio.h"
  44 #include "myassert.h"
  45 #include "arc.h"
  46 #include "arctess.h"
  47 #include "bezierarc.h"
  48 #include "bin.h"
  49 #include "mapdesc.h"
  50 #include "nurbsconsts.h"
  51 #include "subdivider.h"
  52
  53 /*-----------------------------------------------------------------------------
  54  * Subdivider::decompose - break all curves into monotone arcs
  55  *-----------------------------------------------------------------------------
  56  */
  57 int
  58 Subdivider::decompose( Bin& bin, REAL geo_stepsize )
  59 {
  60     Arc_ptr jarc;
  61     for( jarc=bin.firstarc(); jarc; jarc=bin.nextarc() ) {
  62         if( ! jarc->isTessellated() ) {
  63             /* points have not been transformed, therefore they may be either
  64                homogeneous or inhomogeneous */
  65             tessellate( jarc, geo_stepsize );
  66             if( jarc->isDisconnected() || jarc->next->isDisconnected() )
  67                 return 1;
  68         }
  69     }
  70
  71     for( jarc=bin.firstarc(); jarc; jarc=bin.nextarc() ) {
  72         monotonize( jarc, bin );
  73     }
  74
  75 #ifndef NDEBUG
  76     for( jarc=bin.firstarc(); jarc; jarc=bin.nextarc() ) {
  77         assert( isMonotone( jarc ) != 0 );
  78     }
  79 #endif
  80
  81     return 0;
  82 }
  83
  84 void
  85 Subdivider::tessellate( Arc_ptr jarc, REAL geo_stepsize )
  86 {
  87     BezierArc *b = jarc->bezierArc;
  88     Mapdesc *mapdesc = b->mapdesc;
  89
  90     if( mapdesc->isRational() ) {
  91         REAL max = mapdesc->calcVelocityRational( b->cpts, b->stride, b->order );
  92         REAL arc_stepsize = (max > 1.0) ? (1.0/max) : 1.0;
  93         if( jarc->bezierArc->order != 2 )
  94             arctessellator.tessellateNonlinear( jarc, geo_stepsize, arc_stepsize, 1 );
  95         else {
  96             arctessellator.tessellateLinear( jarc, geo_stepsize, arc_stepsize, 1 );
  97         }
  98     } else {
  99         REAL max = mapdesc->calcVelocityNonrational( b->cpts, b->stride, b->order );
 100         REAL arc_stepsize = (max > 1.0) ? (1.0/max) : 1.0;
 101         if( jarc->bezierArc->order != 2 )
 102             arctessellator.tessellateNonlinear( jarc, geo_stepsize, arc_stepsize, 0 );
 103         else {
 104             arctessellator.tessellateLinear( jarc, geo_stepsize, arc_stepsize, 0 );
 105         }
 106     }
 107 }
 108
 109 /*-------------------------------------------------------------------------
 110  * Subdivider::monotonize - break up a jordan arc into s,t-monotone
 111  *      components.  This code will remove degenerate segments, including
 112  *      arcs of only a single point.
 113  *-------------------------------------------------------------------------
 114  */
 115 void
 116 Subdivider::monotonize( Arc_ptr jarc, Bin& bin )
 117 {
 118     TrimVertex  *firstvert = jarc->pwlArc->pts;
 119     TrimVertex  *lastvert = firstvert + (jarc->pwlArc->npts - 1);
 120     long        uid = jarc->nuid;
 121     arc_side    side = jarc->getside();
 122     dir         sdir = none;
 123     dir         tdir = none;
 124     int         degenerate = 1;
 125
 126     int         nudegenerate;
 127     int         change;
 128
 129     TrimVertex *vert;
 130     for( vert = firstvert; vert != lastvert; vert++ ) {
 131
 132         nudegenerate = 1;
 133         change = 0;
 134
 135         /* check change relative to s axis, clear degenerate bit if needed */
 136         REAL sdiff = vert[1].param[0] - vert[0].param[0];
 137         if( sdiff == 0 ) {
 138             if( sdir != same ) {
 139                 sdir = same;
 140                 change = 1;
 141             }
 142         } else if( sdiff < 0.0 ) {
 143             if( sdir != down ) {
 144                 sdir = down;
 145                 change = 1;
 146             }
 147             nudegenerate = 0;
 148         } else {
 149             if( sdir != up ) {
 150                 sdir = up;
 151                 change = 1;
 152             }
 153             nudegenerate = 0;
 154         }
 155
 156         /* check change relative to t axis, clear degenerate bit if needed */
 157         REAL tdiff = vert[1].param[1] - vert[0].param[1];
 158         if( tdiff == 0 ) {
 159             if( tdir != same ) {
 160                 tdir = same;
 161                 change = 1;
 162             }
 163         } else if( tdiff < 0.0 ) {
 164             if( tdir != down ) {
 165                 tdir = down;
 166                 change = 1;
 167             }
 168             nudegenerate = 0;
 169         } else {
 170             if( tdir != up ) {
 171                 tdir = up;
 172                 change = 1;
 173             }
 174             nudegenerate = 0;
 175         }
 176
 177         if( change ) {
 178             if( ! degenerate ) {
 179                 /* make last segment into separate pwl curve */
 180                 jarc->pwlArc->npts = vert - firstvert + 1;
 181                 jarc = (new(arcpool) Arc( side, uid ))->append( jarc );
 182                 jarc->pwlArc = new(pwlarcpool) PwlArc();
 183                 bin.addarc( jarc );
 184             }
 185             firstvert = jarc->pwlArc->pts = vert;
 186             degenerate = nudegenerate;
 187         }
 188     }
 189     jarc->pwlArc->npts = vert - firstvert + 1;
 190
 191     if( degenerate ) {
 192         /* remove jarc from circularly linked list */
 193         jarc->prev->next = jarc->next;
 194         jarc->next->prev = jarc->prev;
 195
 196         assert( jarc->prev->check(  ) != 0 );
 197         assert( jarc->next->check(  ) != 0 );
 198
 199         /* remove jarc from bin */
 200         bin.remove_this_arc( jarc  );
 201
 202         jarc->pwlArc->deleteMe( pwlarcpool ); jarc->pwlArc = 0;
 203         jarc->deleteMe( arcpool );
 204     }
 205 }
 206
 207 /*-------------------------------------------------------------------------
 208  * Subdivider::isMonotone - return true if arc is monotone AND non-degenerate
 209  *-------------------------------------------------------------------------
 210  */
 211 int
 212 Subdivider::isMonotone( Arc_ptr jarc )
 213 {
 214     TrimVertex  *firstvert = jarc->pwlArc->pts;
 215     TrimVertex  *lastvert = firstvert + (jarc->pwlArc->npts - 1);
 216
 217     if( firstvert == lastvert ) return 1;
 218
 219     TrimVertex  *vert = firstvert;
 220     enum dir    sdir;
 221     enum dir    tdir;
 222
 223     REAL diff = vert[1].param[0] - vert[0].param[0];
 224     if( diff == 0.0 )
 225         sdir = same;
 226     else if( diff < 0.0 )
 227         sdir = down;
 228     else
 229         sdir = up;
 230
 231     diff = vert[1].param[1] - vert[0].param[1];
 232     if( diff == 0.0 )
 233         tdir = same;
 234     else if( diff < 0.0 )
 235         tdir = down;
 236     else
 237         tdir = up;
 238
 239     if( (sdir == same) && (tdir == same) ) return 0;
 240
 241     for( ++vert ; vert != lastvert; vert++ ) {
 242         diff = vert[1].param[0] - vert[0].param[0];
 243         if( diff == 0.0 ) {
 244             if( sdir != same ) return 0;
 245         } else if( diff < 0.0 ) {
 246             if( sdir != down ) return 0;
 247         } else {
 248             if( sdir != up ) return 0;
 249         }
 250
 251         diff = vert[1].param[1] - vert[0].param[1];
 252         if( diff == 0.0 ) {
 253             if( tdir != same ) return 0;
 254         } else if( diff < 0.0 ) {
 255             if( tdir != down ) return 0;
 256         } else {
 257             if( tdir != up ) return 0;
 258         }
 259     }
 260     return 1;
 261 }
 262