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