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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.
#include "precompiled.h"
#include "Plane.h"
#include "MathUtil.h"
CPlane::CPlane ()
{
m_Dist = 0.0f;
}
//sets the plane equation from 3 points on that plane
void CPlane::Set (const CVector3D &p1, const CVector3D &p2, const CVector3D &p3)
{
CVector3D D1, D2;
CVector3D Norm;
//calculate two vectors on the surface of the plane
D1 = p2-p1;
D2 = p3-p1;
//cross multiply gives normal
Norm = D2.Cross(D1);
Set (Norm, p1);
}
//sets the plane equation from a normal and a point on
//that plane
void CPlane::Set (const CVector3D &norm, const CVector3D &point)
{
m_Norm = norm;
m_Dist = - (norm.X * point.X +
norm.Y * point.Y +
norm.Z * point.Z);
// Normalize ();
}
//normalizes the plane equation
void CPlane::Normalize ()
{
float Scale;
Scale = 1.0f/m_Norm.Length ();
m_Norm.X *= Scale;
m_Norm.Y *= Scale;
m_Norm.Z *= Scale;
m_Dist *= Scale;
}
//returns the side of the plane on which this point
//lies.
PLANESIDE CPlane::ClassifyPoint (const CVector3D &point) const
{
float Dist;
Dist = m_Norm.X * point.X +
m_Norm.Y * point.Y +
m_Norm.Z * point.Z +
m_Dist;
const float EPS = 0.001f;
if (Dist > EPS)
return PS_FRONT;
else if (Dist < -EPS)
return PS_BACK;
return PS_ON;
}
//calculates the intersection point of a line with this
//plane. Returns false if there is no intersection
bool CPlane::FindLineSegIntersection (const CVector3D &start, const CVector3D &end, CVector3D *intsect)
{
float dist1 = DistanceToPlane( start );
float dist2 = DistanceToPlane( end );
if( (dist1 < 0 && dist2 < 0) || (dist1 >= 0 && dist2 >= 0) )
return false;
float t = (-dist1) / (dist2-dist1);
*intsect = Interpolate( start, end, t );
return true;
}
bool CPlane::FindRayIntersection (const CVector3D &start, const CVector3D &direction, CVector3D *intsect)
{
float dot = m_Norm.Dot (direction);
if (dot == 0.0f)
return false;
*intsect = start - (direction * (DistanceToPlane (start)/dot));
return true;
}
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