src/glu/sgi/libnurbs/internals/knotvector.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  * knotvector.c++
  37  *
  38  */
  39
  40 #include "glimports.h"
  41 #include "mystdio.h"
  42 #include "myassert.h"
  43 #include "knotvector.h"
  44 #include "defines.h"
  45
  46 #ifdef __WATCOMC__
  47 #pragma warning 726 10
  48 #endif
  49
  50 void Knotvector::init( long _knotcount, long _stride, long _order, INREAL *_knotlist )
  51 {
  52     knotcount = _knotcount;
  53     stride = _stride;
  54     order = _order;
  55     knotlist = new Knot[_knotcount];
  56     assert( knotlist != 0 );
  57
  58     for( int i = 0; i != _knotcount; i++ )
  59         knotlist[i] = (Knot) _knotlist[i];
  60 }
  61
  62 Knotvector::Knotvector( void )
  63 {
  64     knotcount = 0;
  65     stride = 0;
  66     order = 0;
  67     knotlist = 0;
  68 }
  69
  70 Knotvector::~Knotvector( void )
  71 {
  72     if( knotlist ) delete[] knotlist;
  73 }
  74
  75 int Knotvector::validate( void )
  76 {
  77    /* kindex is used as an array index so subtract one first,
  78      * this propagates throughout the code so study carefully */
  79     long        kindex = knotcount-1;
  80
  81     if( order < 1 || order > MAXORDER ) {
  82         // spline order un-supported
  83         return( 1 );
  84     }
  85
  86     if( knotcount < (2 * order) ) {
  87         // too few knots
  88         return( 2 );
  89     }
  90
  91     if( identical( knotlist[kindex-(order-1)], knotlist[order-1]) ) {
  92         // valid knot range is empty
  93         return( 3 );
  94     }
  95
  96     for( long i = 0; i < kindex; i++)
  97         if( knotlist[i] > knotlist[i+1] ) {
  98             // decreasing knot sequence
  99             return( 4 );
 100         }
 101
 102     /* check for valid multiplicity */
 103
 104     /*  kindex is currently the index of the last knot.
 105      *  In the next loop  it is decremented to ignore the last knot
 106      *  and the loop stops when kindex  is 2 so as to ignore the first
 107      *  knot as well.  These knots are not used in computing
 108      *  knot multiplicities.
 109      */
 110
 111     long multi = 1;
 112     for( ; kindex >= 1; kindex-- ) {
 113         if( knotlist[kindex] - knotlist[kindex-1] < TOLERANCE ) {
 114             multi++;
 115             continue;
 116         }
 117         if ( multi > order ) {
 118             // knot multiplicity greater than order of spline
 119             return( 5 );
 120         }
 121         multi = 1;
 122     }
 123
 124     if ( multi > order ) {
 125         // knot multiplicity greater than order of spline
 126         return( 5 );
 127     }
 128
 129     return 0;
 130 }
 131
 132 void Knotvector::show( const char *msg )
 133 {
 134 #ifndef NDEBUG
 135     _glu_dprintf( "%s\n", msg );
 136     _glu_dprintf( "order = %ld, count = %ld\n", order, knotcount );
 137
 138     for( int i=0; i<knotcount; i++ )
 139         _glu_dprintf( "knot[%d] = %g\n", i, knotlist[i] );
 140 #endif
 141 }
 142