G3D::ConvexPolygon2D Class Reference

#include <ConvexPolyhedron.h>

Public Member Functions
	ConvexPolygon2D ()
	ConvexPolygon2D (const Array< Vector2 > &pts, bool reverse=false)
int	numVertices () const
const Vector2 &	vertex (int index) const
bool	contains (const Vector2 &p, bool reverseWinding=false) const

Private Attributes
Array< Vector2 >	m_vertex

Constructor & Destructor Documentation

G3D::ConvexPolygon2D::ConvexPolygon2D ( )

inline

{}

G3D::ConvexPolygon2D::ConvexPolygon2D	(	const Array< Vector2 > &	pts,
		bool	reverse = false
	)

Points are counter-clockwise in a Y = down, X = right coordinate system.

Parameters

reverse

If true, the points are reversed (i.e. winding direction is changed) before the polygon is created.

 : m_vertex(pts) {
 if (reverse) {
 m_vertex.reverse();
 }
}

Member Function Documentation

bool G3D::ConvexPolygon2D::contains	(	const Vector2 &	p,
		bool	reverseWinding = false
	)		const

Parameters

reverseWinding

If true, the winding direction of the polygon is reversed for this test.

 {
 // Compute the signed area of each polygon from p to an edge. 
 // If the area is non-negative for all polygons then p is inside 
 // the polygon. (To adapt this algorithm for a concave polygon,
 // the *sum* of the areas must be non-negative).

 float r = reverse ? -1.0f : 1.0f;

 for (int i0 = 0; i0 < m_vertex.size(); ++i0) {
 int i1 = (i0 + 1) % m_vertex.size();
 const Vector2& v0 = m_vertex[i0];
 const Vector2& v1 = m_vertex[i1];

 Vector2 e0 = v0 - p;
 Vector2 e1 = v1 - p;

 // Area = (1/2) cross product, negated to be ccw in
 // a 2D space; we neglect the 1/2
 float area = -(e0.x * e1.y - e0.y * e1.x);

 if (area * r < 0) {
 return false;
 }
 }

 return true;
}

int G3D::ConvexPolygon2D::numVertices ( ) const

inline

 {
 return m_vertex.size();
 }

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const Vector2& G3D::ConvexPolygon2D::vertex ( int  index ) const

inline

 {
 debugAssert((index >= 0) && (index <= m_vertex.size()));
 return m_vertex[index];
 }

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Member Data Documentation

Array<Vector2> G3D::ConvexPolygon2D::m_vertex

private

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The documentation for this class was generated from the following files:

• dep/g3dlite/include/G3D/ConvexPolyhedron.h
• dep/g3dlite/source/ConvexPolyhedron.cpp