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/**
@file Box.cpp
Box class
@maintainer Morgan McGuire, http://graphics.cs.williams.edu
@created 2001-06-02
@edited 2008-12-27
*/
#include "G3D/Box2D.h"
#include "G3D/CoordinateFrame.h"
#include "G3D/Rect2D.h"
namespace G3D {
bool Box2D::overlaps1Way(const Box2D& other) const {
for (int a = 0; a < 2; ++a) {
float t = other.m_corner[0].dot(m_axisin[a]);
// Find the extent of box 2 on m_axisin a
float tMin = t;
float tMax = t;
for (int c = 1; c < 4; ++c) {
t = other.m_corner[c].dot(m_axisin[a]);
if (t < tMin) {
tMin = t;
} else if (t > tMax) {
tMax = t;
}
}
// We have to subtract off the origin
// See if [tMin, tMax] intersects [0, 1]
if ((tMin > 1 + origin[a]) || (tMax < origin[a])) {
// There was no intersection along this dimension;
// the boxes cannot possibly overlap.
return false;
}
}
// There was no dimension along which there is no intersection.
// Therefore the boxes overlap.
return true;
}
void Box2D::computeAxes() {
m_axis[0] = m_corner[1] - m_corner[0];
m_axis[1] = m_corner[3] - m_corner[0];
// Make the length of each m_axisin = 1/edge length so we know any
// dot product must be less than 1 to fall within the edge.
float len[2];
for (int a = 0; a < 2; ++a) {
float lenSq = m_axis[a].squaredLength();
m_axisin[a] = m_axis[a] / lenSq;
origin[a] = m_corner[0].dot(m_axisin[a]);
len[a] = sqrt(lenSq);
m_axis[a] /= len[a];
}
// w * h
m_area = len[0] * len[1];
m_center = (m_corner[0] + m_corner[2]) * 0.5f;
}
Box2D::Box2D(const Vector2& center, float w, float h, float angle) {
Vector2 X( cos(angle), sin(angle));
Vector2 Y(-sin(angle), cos(angle));
X *= w / 2;
Y *= h / 2;
m_corner[0] = center - X - Y;
m_corner[1] = center + X - Y;
m_corner[2] = center + X + Y;
m_corner[3] = center - X + Y;
computeAxes();
}
Box2D::Box2D(const AABox2D& b) {
for (int i = 0; i < 4; ++i) {
m_corner[i] = b.corner(i);
}
computeAxes();
}
Box2D::Box2D(const Vector2& min, const Vector2& max) {
*this = Box2D(Rect2D::xyxy(min, max));
}
Box2D::Box2D(const CFrame& frame, Box2D& b) {
for (int i = 0; i < 4; ++i) {
m_corner[i] = frame.pointToWorldSpace(Vector3(b.corner(i), 0)).xy();
}
computeAxes();
}
} // G3D
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