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
|
/* Copyright (C) 2011 Wildfire Games.
* This file is part of 0 A.D.
*
* 0 A.D. is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 2 of the License, or
* (at your option) any later version.
*
* 0 A.D. 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
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with 0 A.D. If not, see <http://www.gnu.org/licenses/>.
*/
#include "precompiled.h"
#include "BoundingBoxOriented.h"
#include "maths/BoundingBoxAligned.h"
#include <float.h>
const CBoundingBoxOriented CBoundingBoxOriented::EMPTY = CBoundingBoxOriented();
CBoundingBoxOriented::CBoundingBoxOriented(const CBoundingBoxAligned& bound)
{
if (bound.IsEmpty())
{
SetEmpty();
}
else
{
bound.GetCentre(m_Center);
// the axes of an AABB are the world-space axes
m_Basis[0].X = 1.f; m_Basis[0].Y = 0.f; m_Basis[0].Z = 0.f;
m_Basis[1].X = 0.f; m_Basis[1].Y = 1.f; m_Basis[1].Z = 0.f;
m_Basis[2].X = 0.f; m_Basis[2].Y = 0.f; m_Basis[2].Z = 1.f;
// element-wise division by two to get half sizes (remember, [1] and [0] are the max and min coord points)
m_HalfSizes = (bound[1] - bound[0]) * 0.5f;
}
}
bool CBoundingBoxOriented::RayIntersect(const CVector3D& origin, const CVector3D& dir, float& tMin_out, float& tMax_out) const
{
// See Real-Time Rendering, Third Edition, p. 743
float tMin = -FLT_MAX;
float tMax = FLT_MAX;
CVector3D p = m_Center - origin;
for (int i = 0; i < 3; ++i)
{
// test the ray for intersections with the slab whose normal vector is m_Basis[i]
float e = m_Basis[i].Dot(p); // distance between the ray origin and the box center projected onto the slab normal
float f = m_Basis[i].Dot(dir); // cosine of the angle between the slab normal and the ray direction
if(fabsf(f) > 1e-10f)
{
// Determine the distances t1 and t2 from the origin of the ray to the points where it intersects
// the slab. See docs/ray_intersect.pdf for why/how this works.
float invF = 1.f/f;
float t1 = (e + m_HalfSizes[i]) * invF;
float t2 = (e - m_HalfSizes[i]) * invF;
// make sure t1 <= t2, swap if necessary
if (t1 > t2)
{
float tmp = t1;
t1 = t2;
t2 = tmp;
}
// update the overall tMin and tMax if necessary
if (t1 > tMin) tMin = t1;
if (t2 < tMax) tMax = t2;
// try to break out of the loop as fast as possible by checking for some conditions
if (tMin > tMax) return false; // ray misses the box
if (tMax < 0) return false; // box is behind the ray origin
}
else
{
// the ray is parallel to the slab currently being tested, or is as close to parallel
// as makes no difference; return false if the ray is outside of the slab.
if (e > m_HalfSizes[i] || -e > m_HalfSizes[i])
return false;
}
}
tMin_out = tMin;
tMax_out = tMax;
return true;
}
|
