DOOM-3-BFG/neo/idlib/math/Plane.cpp

/*
===========================================================================

Doom 3 BFG Edition GPL Source Code
Copyright (C) 1993-2012 id Software LLC, a ZeniMax Media company. 

This file is part of the Doom 3 BFG Edition GPL Source Code ("Doom 3 BFG Edition Source Code").  

Doom 3 BFG Edition Source Code 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 3 of the License, or
(at your option) any later version.

Doom 3 BFG Edition Source Code 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 Doom 3 BFG Edition Source Code.  If not, see <http://www.gnu.org/licenses/>.

In addition, the Doom 3 BFG Edition Source Code is also subject to certain additional terms. You should have received a copy of these additional terms immediately following the terms and conditions of the GNU General Public License which accompanied the Doom 3 BFG Edition Source Code.  If not, please request a copy in writing from id Software at the address below.

If you have questions concerning this license or the applicable additional terms, you may contact in writing id Software LLC, c/o ZeniMax Media Inc., Suite 120, Rockville, Maryland 20850 USA.

===========================================================================
*/

#pragma hdrstop
#include "../precompiled.h"

idPlane plane_origin( 0.0f, 0.0f, 0.0f, 0.0f );

/*
================
idPlane::Type
================
*/
int idPlane::Type() const {
	if ( Normal()[0] == 0.0f ) {
		if ( Normal()[1] == 0.0f ) {
			return Normal()[2] > 0.0f ? PLANETYPE_Z : PLANETYPE_NEGZ;
		}
		else if ( Normal()[2] == 0.0f ) {
			return Normal()[1] > 0.0f ? PLANETYPE_Y : PLANETYPE_NEGY;
		}
		else {
			return PLANETYPE_ZEROX;
		}
	}
	else if ( Normal()[1] == 0.0f ) {
		if ( Normal()[2] == 0.0f ) {
			return Normal()[0] > 0.0f ? PLANETYPE_X : PLANETYPE_NEGX;
		}
		else {
			return PLANETYPE_ZEROY;
		}
	}
	else if ( Normal()[2] == 0.0f ) {
		return PLANETYPE_ZEROZ;
	}
	else {
		return PLANETYPE_NONAXIAL;
	}
}

/*
================
idPlane::HeightFit
================
*/
bool idPlane::HeightFit( const idVec3 *points, const int numPoints ) {
	int i;
	float sumXX = 0.0f, sumXY = 0.0f, sumXZ = 0.0f;
	float sumYY = 0.0f, sumYZ = 0.0f;
	idVec3 sum, average, dir;

	if ( numPoints == 1 ) {
		a = 0.0f;
		b = 0.0f;
		c = 1.0f;
		d = -points[0].z;
		return true;
	}
	if ( numPoints == 2 ) {
		dir = points[1] - points[0];
		Normal() = dir.Cross( idVec3( 0, 0, 1 ) ).Cross( dir );
		Normalize();
		d = -( Normal() * points[0] );
		return true;
	}

	sum.Zero();
	for ( i = 0; i < numPoints; i++) {
		sum += points[i];
	}
	average = sum / numPoints;

	for ( i = 0; i < numPoints; i++ ) {
		dir = points[i] - average;
		sumXX += dir.x * dir.x;
		sumXY += dir.x * dir.y;
		sumXZ += dir.x * dir.z;
		sumYY += dir.y * dir.y;
		sumYZ += dir.y * dir.z;
	}

	idMat2 m( sumXX, sumXY, sumXY, sumYY );
	if ( !m.InverseSelf() ) {
		return false;
	}

	a = - sumXZ * m[0][0] - sumYZ * m[0][1];
	b = - sumXZ * m[1][0] - sumYZ * m[1][1];
	c = 1.0f;
	Normalize();
	d = -( a * average.x + b * average.y + c * average.z );
	return true;
}

/*
================
idPlane::PlaneIntersection
================
*/
bool idPlane::PlaneIntersection( const idPlane &plane, idVec3 &start, idVec3 &dir ) const {
	double n00, n01, n11, det, invDet, f0, f1;

	n00 = Normal().LengthSqr();
	n01 = Normal() * plane.Normal();
	n11 = plane.Normal().LengthSqr();
	det = n00 * n11 - n01 * n01;

	if ( idMath::Fabs(det) < 1e-6f ) {
		return false;
	}

	invDet = 1.0f / det;
	f0 = ( n01 * plane.d - n11 * d ) * invDet;
	f1 = ( n01 * d - n00 * plane.d ) * invDet;

	dir = Normal().Cross( plane.Normal() );
	start = f0 * Normal() + f1 * plane.Normal();
	return true;
}

/*
=============
idPlane::ToString
=============
*/
const char *idPlane::ToString( int precision ) const {
	return idStr::FloatArrayToString( ToFloatPtr(), GetDimension(), precision );
}