Plane.h

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/* Copyright (C) 2009 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/>.
 */
 
/*
 * A Plane in R3 and several utility methods.
 */
 
// Note that the format used for the plane equation is
// Ax + By + Cz + D = 0, where <A,B,C> is the normal vector.
 
#ifndef INCLUDED_PLANE
#define INCLUDED_PLANE
 
#include "Vector3D.h"
#include "Vector4D.h"
 
enum PLANESIDE
{
    PS_FRONT,
    PS_BACK,
    PS_ON
};
 
class CPlane
{
    public:
        CPlane();
        CPlane(const CVector4D& coeffs) : m_Norm(coeffs.X, coeffs.Y, coeffs.Z), m_Dist(coeffs.W) { }
 
        //sets the plane equation from 3 points on that plane
        void Set(const CVector3D& p1, const CVector3D& p2, const CVector3D& p3);
 
        //sets the plane equation from a normal and a point on
        //that plane
        void Set(const CVector3D& norm, const CVector3D& point);
 
        //normalizes the plane equation
        void Normalize();
 
        //returns the side of the plane on which this point lies
        PLANESIDE ClassifyPoint(const CVector3D& point) const;
        //returns true if this point is on the back side
        inline bool IsPointOnBackSide(const CVector3D& point) const;
 
        //solves the plane equation for a particular point
        inline float DistanceToPlane(const CVector3D& point) const;
 
        //calculates the intersection point of a line with this
        //plane. Returns false if there is no intersection
        bool FindLineSegIntersection(const CVector3D& start, const CVector3D& end, CVector3D* intsect) const;
        bool FindRayIntersection(const CVector3D& start, const CVector3D& direction, CVector3D* intsect) const;
 
    public:
        CVector3D m_Norm;   //normal vector of the plane
        float m_Dist;       //Plane distance (ie D in the plane eq.)
        static const float m_EPS;
};
 
float CPlane::DistanceToPlane(const CVector3D& point) const
{
    return m_Norm.X * point.X + m_Norm.Y * point.Y + m_Norm.Z * point.Z + m_Dist;
}
 
bool CPlane::IsPointOnBackSide(const CVector3D& point) const
{
    return DistanceToPlane(point) < -m_EPS;
}
 
#endif