3 -----------------------------------------------------------------------------
4 This source file is part of GIMPACT Library.
6 For the latest info, see http://gimpact.sourceforge.net/
8 Copyright (c) 2006 Francisco Leon Najera. C.C. 80087371.
9 email: projectileman@yahoo.com
11 This library is free software; you can redistribute it and/or
12 modify it under the terms of EITHER:
13 (1) The GNU Lesser General Public License as published by the Free
14 Software Foundation; either version 2.1 of the License, or (at
15 your option) any later version. The text of the GNU Lesser
16 General Public License is included with this library in the
17 file GIMPACT-LICENSE-LGPL.TXT.
18 (2) The BSD-style license that is included with this library in
19 the file GIMPACT-LICENSE-BSD.TXT.
20 (3) The zlib/libpng license that is included with this library in
21 the file GIMPACT-LICENSE-ZLIB.TXT.
23 This library is distributed in the hope that it will be useful,
24 but WITHOUT ANY WARRANTY; without even the implied warranty of
25 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the files
26 GIMPACT-LICENSE-LGPL.TXT, GIMPACT-LICENSE-ZLIB.TXT and GIMPACT-LICENSE-BSD.TXT for more details.
28 -----------------------------------------------------------------------------
31 #include "gim_box_set.h"
33 GUINT GIM_BOX_TREE::_calc_splitting_axis(
34 gim_array<GIM_AABB_DATA>& primitive_boxes, GUINT startIndex, GUINT endIndex)
38 btVector3 means(btScalar(0.), btScalar(0.), btScalar(0.));
39 btVector3 variance(btScalar(0.), btScalar(0.), btScalar(0.));
40 GUINT numIndices = endIndex - startIndex;
42 for (i = startIndex; i < endIndex; i++)
44 btVector3 center = btScalar(0.5) * (primitive_boxes[i].m_bound.m_max +
45 primitive_boxes[i].m_bound.m_min);
48 means *= (btScalar(1.) / (btScalar)numIndices);
50 for (i = startIndex; i < endIndex; i++)
52 btVector3 center = btScalar(0.5) * (primitive_boxes[i].m_bound.m_max +
53 primitive_boxes[i].m_bound.m_min);
54 btVector3 diff2 = center - means;
55 diff2 = diff2 * diff2;
58 variance *= (btScalar(1.) / ((btScalar)numIndices - 1));
60 return variance.maxAxis();
63 GUINT GIM_BOX_TREE::_sort_and_calc_splitting_index(
64 gim_array<GIM_AABB_DATA>& primitive_boxes, GUINT startIndex,
65 GUINT endIndex, GUINT splitAxis)
68 GUINT splitIndex = startIndex;
69 GUINT numIndices = endIndex - startIndex;
72 btScalar splitValue = 0.0f;
73 for (i = startIndex; i < endIndex; i++)
75 splitValue += 0.5f * (primitive_boxes[i].m_bound.m_max[splitAxis] +
76 primitive_boxes[i].m_bound.m_min[splitAxis]);
78 splitValue /= (btScalar)numIndices;
80 //sort leafNodes so all values larger then splitValue comes first, and smaller values start from 'splitIndex'.
81 for (i = startIndex; i < endIndex; i++)
83 btScalar center = 0.5f * (primitive_boxes[i].m_bound.m_max[splitAxis] +
84 primitive_boxes[i].m_bound.m_min[splitAxis]);
85 if (center > splitValue)
88 primitive_boxes.swap(i, splitIndex);
93 //if the splitIndex causes unbalanced trees, fix this by using the center in between startIndex and endIndex
94 //otherwise the tree-building might fail due to stack-overflows in certain cases.
95 //unbalanced1 is unsafe: it can cause stack overflows
96 //bool unbalanced1 = ((splitIndex==startIndex) || (splitIndex == (endIndex-1)));
98 //unbalanced2 should work too: always use center (perfect balanced trees)
99 //bool unbalanced2 = true;
101 //this should be safe too:
102 GUINT rangeBalancedIndices = numIndices / 3;
103 bool unbalanced = ((splitIndex <= (startIndex + rangeBalancedIndices)) || (splitIndex >= (endIndex - 1 - rangeBalancedIndices)));
107 splitIndex = startIndex + (numIndices >> 1);
110 btAssert(!((splitIndex == startIndex) || (splitIndex == (endIndex))));
115 void GIM_BOX_TREE::_build_sub_tree(gim_array<GIM_AABB_DATA>& primitive_boxes, GUINT startIndex, GUINT endIndex)
117 GUINT current_index = m_num_nodes++;
119 btAssert((endIndex - startIndex) > 0);
121 if ((endIndex - startIndex) == 1) //we got a leaf
123 m_node_array[current_index].m_left = 0;
124 m_node_array[current_index].m_right = 0;
125 m_node_array[current_index].m_escapeIndex = 0;
127 m_node_array[current_index].m_bound = primitive_boxes[startIndex].m_bound;
128 m_node_array[current_index].m_data = primitive_boxes[startIndex].m_data;
132 //configure inner node
136 //calc this node bounding box
137 m_node_array[current_index].m_bound.invalidate();
138 for (splitIndex = startIndex; splitIndex < endIndex; splitIndex++)
140 m_node_array[current_index].m_bound.merge(primitive_boxes[splitIndex].m_bound);
143 //calculate Best Splitting Axis and where to split it. Sort the incoming 'leafNodes' array within range 'startIndex/endIndex'.
146 splitIndex = _calc_splitting_axis(primitive_boxes, startIndex, endIndex);
148 splitIndex = _sort_and_calc_splitting_index(
149 primitive_boxes, startIndex, endIndex, splitIndex);
151 //configure this inner node : the left node index
152 m_node_array[current_index].m_left = m_num_nodes;
153 //build left child tree
154 _build_sub_tree(primitive_boxes, startIndex, splitIndex);
156 //configure this inner node : the right node index
157 m_node_array[current_index].m_right = m_num_nodes;
159 //build right child tree
160 _build_sub_tree(primitive_boxes, splitIndex, endIndex);
162 //configure this inner node : the escape index
163 m_node_array[current_index].m_escapeIndex = m_num_nodes - current_index;
166 //! stackless build tree
167 void GIM_BOX_TREE::build_tree(
168 gim_array<GIM_AABB_DATA>& primitive_boxes)
170 // initialize node count to 0
173 m_node_array.resize(primitive_boxes.size() * 2);
175 _build_sub_tree(primitive_boxes, 0, primitive_boxes.size());