1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
|
/*
-----------------------------------------------------------------------------
This source file is part of GIMPACT Library.
For the latest info, see http://gimpact.sourceforge.net/
Copyright (c) 2006 Francisco Leon Najera. C.C. 80087371.
email: projectileman@yahoo.com
This library is free software; you can redistribute it and/or
modify it under the terms of EITHER:
(1) The GNU Lesser General Public License as published by the Free
Software Foundation; either version 2.1 of the License, or (at
your option) any later version. The text of the GNU Lesser
General Public License is included with this library in the
file GIMPACT-LICENSE-LGPL.TXT.
(2) The BSD-style license that is included with this library in
the file GIMPACT-LICENSE-BSD.TXT.
(3) The zlib/libpng license that is included with this library in
the file GIMPACT-LICENSE-ZLIB.TXT.
This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the files
GIMPACT-LICENSE-LGPL.TXT, GIMPACT-LICENSE-ZLIB.TXT and GIMPACT-LICENSE-BSD.TXT for more details.
-----------------------------------------------------------------------------
*/
#include "gim_box_set.h"
GUINT GIM_BOX_TREE::_calc_splitting_axis(
gim_array<GIM_AABB_DATA> & primitive_boxes, GUINT startIndex, GUINT endIndex)
{
GUINT i;
btVector3 means(btScalar(0.),btScalar(0.),btScalar(0.));
btVector3 variance(btScalar(0.),btScalar(0.),btScalar(0.));
GUINT numIndices = endIndex-startIndex;
for (i=startIndex;i<endIndex;i++)
{
btVector3 center = btScalar(0.5)*(primitive_boxes[i].m_bound.m_max +
primitive_boxes[i].m_bound.m_min);
means+=center;
}
means *= (btScalar(1.)/(btScalar)numIndices);
for (i=startIndex;i<endIndex;i++)
{
btVector3 center = btScalar(0.5)*(primitive_boxes[i].m_bound.m_max +
primitive_boxes[i].m_bound.m_min);
btVector3 diff2 = center-means;
diff2 = diff2 * diff2;
variance += diff2;
}
variance *= (btScalar(1.)/ ((btScalar)numIndices-1) );
return variance.maxAxis();
}
GUINT GIM_BOX_TREE::_sort_and_calc_splitting_index(
gim_array<GIM_AABB_DATA> & primitive_boxes, GUINT startIndex,
GUINT endIndex, GUINT splitAxis)
{
GUINT i;
GUINT splitIndex =startIndex;
GUINT numIndices = endIndex - startIndex;
// average of centers
btScalar splitValue = 0.0f;
for (i=startIndex;i<endIndex;i++)
{
splitValue+= 0.5f*(primitive_boxes[i].m_bound.m_max[splitAxis] +
primitive_boxes[i].m_bound.m_min[splitAxis]);
}
splitValue /= (btScalar)numIndices;
//sort leafNodes so all values larger then splitValue comes first, and smaller values start from 'splitIndex'.
for (i=startIndex;i<endIndex;i++)
{
btScalar center = 0.5f*(primitive_boxes[i].m_bound.m_max[splitAxis] +
primitive_boxes[i].m_bound.m_min[splitAxis]);
if (center > splitValue)
{
//swap
primitive_boxes.swap(i,splitIndex);
splitIndex++;
}
}
//if the splitIndex causes unbalanced trees, fix this by using the center in between startIndex and endIndex
//otherwise the tree-building might fail due to stack-overflows in certain cases.
//unbalanced1 is unsafe: it can cause stack overflows
//bool unbalanced1 = ((splitIndex==startIndex) || (splitIndex == (endIndex-1)));
//unbalanced2 should work too: always use center (perfect balanced trees)
//bool unbalanced2 = true;
//this should be safe too:
GUINT rangeBalancedIndices = numIndices/3;
bool unbalanced = ((splitIndex<=(startIndex+rangeBalancedIndices)) || (splitIndex >=(endIndex-1-rangeBalancedIndices)));
if (unbalanced)
{
splitIndex = startIndex+ (numIndices>>1);
}
bool unbal = (splitIndex==startIndex) || (splitIndex == (endIndex));
btAssert(!unbal);
return splitIndex;
}
void GIM_BOX_TREE::_build_sub_tree(gim_array<GIM_AABB_DATA> & primitive_boxes, GUINT startIndex, GUINT endIndex)
{
GUINT current_index = m_num_nodes++;
btAssert((endIndex-startIndex)>0);
if((endIndex-startIndex) == 1) //we got a leaf
{
m_node_array[current_index].m_left = 0;
m_node_array[current_index].m_right = 0;
m_node_array[current_index].m_escapeIndex = 0;
m_node_array[current_index].m_bound = primitive_boxes[startIndex].m_bound;
m_node_array[current_index].m_data = primitive_boxes[startIndex].m_data;
return;
}
//configure inner node
GUINT splitIndex;
//calc this node bounding box
m_node_array[current_index].m_bound.invalidate();
for (splitIndex=startIndex;splitIndex<endIndex;splitIndex++)
{
m_node_array[current_index].m_bound.merge(primitive_boxes[splitIndex].m_bound);
}
//calculate Best Splitting Axis and where to split it. Sort the incoming 'leafNodes' array within range 'startIndex/endIndex'.
//split axis
splitIndex = _calc_splitting_axis(primitive_boxes,startIndex,endIndex);
splitIndex = _sort_and_calc_splitting_index(
primitive_boxes,startIndex,endIndex,splitIndex);
//configure this inner node : the left node index
m_node_array[current_index].m_left = m_num_nodes;
//build left child tree
_build_sub_tree(primitive_boxes, startIndex, splitIndex );
//configure this inner node : the right node index
m_node_array[current_index].m_right = m_num_nodes;
//build right child tree
_build_sub_tree(primitive_boxes, splitIndex ,endIndex);
//configure this inner node : the escape index
m_node_array[current_index].m_escapeIndex = m_num_nodes - current_index;
}
//! stackless build tree
void GIM_BOX_TREE::build_tree(
gim_array<GIM_AABB_DATA> & primitive_boxes)
{
// initialize node count to 0
m_num_nodes = 0;
// allocate nodes
m_node_array.resize(primitive_boxes.size()*2);
_build_sub_tree(primitive_boxes, 0, primitive_boxes.size());
}
|
