dlls/d3dx8/mesh.c

   1 /*
   2  * Copyright 2008 David Adam
   3  *
   4  * This library is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU Lesser General Public
   6  * License as published by the Free Software Foundation; either
   7  * version 2.1 of the License, or (at your option) any later version.
   8  *
   9  * This library is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12  * Lesser General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU Lesser General Public
  15  * License along with this library; if not, write to the Free Software
  16  * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA
  17  */
  18
  19 #include "windef.h"
  20 #include "wingdi.h"
  21 #include "d3dx8.h"
  22
  23 BOOL WINAPI D3DXBoxBoundProbe(CONST D3DXVECTOR3 *pmin, CONST D3DXVECTOR3 *pmax, CONST D3DXVECTOR3 *prayposition, CONST D3DXVECTOR3 *praydirection)
  24
  25 /* Algorithm taken from the article: An Efficient and Robust Ray-Box Intersection Algoritm
  26 Amy Williams             University of Utah
  27 Steve Barrus             University of Utah
  28 R. Keith Morley          University of Utah
  29 Peter Shirley            University of Utah
  30
  31 International Conference on Computer Graphics and Interactive Techniques  archive
  32 ACM SIGGRAPH 2005 Courses
  33 Los Angeles, California
  34
  35 This algorithm is free of patents or of copyrights, as confirmed by Peter Shirley himself.
  36
  37 Algorithm: Consider the box as the intersection of three slabs. Clip the ray
  38 against each slab, if there's anything left of the ray after we're
  39 done we've got an intersection of the ray with the box.
  40 */
  41
  42 {
  43     FLOAT div, tmin, tmax, tymin, tymax, tzmin, tzmax;
  44
  45     div = 1.0f / praydirection->x;
  46     if ( div >= 0.0f )
  47     {
  48      tmin = ( pmin->x - prayposition->x ) * div;
  49      tmax = ( pmax->x - prayposition->x ) * div;
  50     }
  51     else
  52     {
  53      tmin = ( pmax->x - prayposition->x ) * div;
  54      tmax = ( pmin->x - prayposition->x ) * div;
  55     }
  56
  57     if ( tmax < 0.0f ) return FALSE;
  58
  59     div = 1.0f / praydirection->y;
  60     if ( div >= 0.0f )
  61     {
  62      tymin = ( pmin->y - prayposition->y ) * div;
  63      tymax = ( pmax->y - prayposition->y ) * div;
  64     }
  65     else
  66     {
  67      tymin = ( pmax->y - prayposition->y ) * div;
  68      tymax = ( pmin->y - prayposition->y ) * div;
  69     }
  70
  71     if ( ( tymax < 0.0f ) || ( tmin > tymax ) || ( tymin > tmax ) ) return FALSE;
  72
  73     if ( tymin > tmin ) tmin = tymin;
  74     if ( tymax < tmax ) tmax = tymax;
  75
  76     div = 1.0f / praydirection->z;
  77     if ( div >= 0.0f )
  78     {
  79      tzmin = ( pmin->z - prayposition->z ) * div;
  80      tzmax = ( pmax->z - prayposition->z ) * div;
  81     }
  82     else
  83     {
  84      tzmin = ( pmax->z - prayposition->z ) * div;
  85      tzmax = ( pmin->z - prayposition->z ) * div;
  86     }
  87
  88     if ( (tzmax < 0.0f ) || ( tmin > tzmax ) || ( tzmin > tmax ) ) return FALSE;
  89
  90     return TRUE;
  91 }
  92
  93 BOOL WINAPI D3DXSphereBoundProbe(CONST D3DXVECTOR3 *pcenter, FLOAT radius, CONST D3DXVECTOR3 *prayposition, CONST D3DXVECTOR3 *praydirection)
  94 {
  95     D3DXVECTOR3 difference;
  96     FLOAT a, b, c, d;
  97
  98     a = D3DXVec3LengthSq(praydirection);
  99     if (!D3DXVec3Subtract(&difference, prayposition, pcenter)) return FALSE;
 100     b = D3DXVec3Dot(&difference, praydirection);
 101     c = D3DXVec3LengthSq(&difference) - radius * radius;
 102     d = b * b - a * c;
 103
 104     if ( ( d <= 0.0f ) || ( sqrt(d) <= b ) ) return FALSE;
 105     return TRUE;
 106 }