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/**
@file Box2D.h
@maintainer Morgan McGuire, http://graphics.cs.williams.edu
@created 2001-06-02
@edited 2008-12-27
Copyright 2000-2009, Morgan McGuire.
All rights reserved.
*/
#ifndef G3D_Box2D_h
#define G3D_Box2D_h
#include "G3D/platform.h"
#include "G3D/Vector2.h"
namespace G3D {
class CoordinateFrame;
typedef class CoordinateFrame CFrame;
class Rect2D;
typedef class Rect2D AABox2D;
/**
2D oriented box
@cite http://www.flipcode.com/archives/2D_OBB_Intersection.shtml
*/
class Box2D {
private:
/** Corners of the box, where 0 is the lower left. */
Vector2 m_corner[4];
/** Two edges of the box extended away from corner[0], with length
= 1 / extentSquared */
Vector2 m_axisin[2];
/** Two edges of the box extended away from corner[0], with unit length */
Vector2 m_axis[2];
/** Centroid of the box */
Vector2 m_center;
/** origin[a] = m_corner[0].dot(m_axisin[a]); */
float origin[2];
/** Surface area */
float m_area;
Vector2 m_extent;
/** Returns true if other overlaps one dimension of this. */
bool overlaps1Way(const Box2D& other) const;
/** Updates the axes after the m_corners move. Assumes the
m_corners actually form a rectangle. */
void computeAxes();
public:
/**
@param center World-space center
@param w Width along object-space x-axis
@param h Height along object-space y-axis
@param angle Counter-clockwise angle from object-space x-axis in radians
*/
Box2D(const Vector2& center = Vector2(0, 0), float w = 0, float h = 0, float angle = 0);
Box2D(const AABox2D& b);
Box2D(const Vector2& min, const Vector2& max);
/** Transform @a b by @a frame, discarding the Z components, and
compute the new box.*/
Box2D(const CFrame& frame, Box2D& b);
inline bool contains(const Vector2& v) const {
// Take to object space:
const Vector2& p = v - m_center;
float x = p.dot(m_axisin[0]);
float y = p.dot(m_axisin[1]);
// Must be within extent/2 on both axes in object space
return (abs(x) <= 0.5f) && (abs(y) <= 0.5f);
}
/** @brief Distance from corner(0) to the next corner along the box's local axis a. */
inline const Vector2& extent() const {
return m_extent;
}
/** @brief Unit length vector along axis @a a */
inline const Vector2& axis(int a) const {
debugAssert(a == 0 || a == 1);
return m_axis[a];
}
/** @brief Surface area */
inline float area() const {
return m_area;
}
inline const Vector2& corner(int i) const {
debugAssert(i >=0 && i <= 3);
return m_corner[i];
}
inline const Vector2& center() const {
return m_center;
}
/** Returns true if the intersection of the boxes is non-empty. */
inline bool overlaps(const Box2D& other) const {
return overlaps1Way(other) && other.overlaps1Way(*this);
}
};
} // G3D
#endif
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