scummvm/graphics/line2d.cpp

/* Residual - A 3D game interpreter
 *
 * Residual is the legal property of its developers, whose names
 * are too numerous to list here. Please refer to the COPYRIGHT
 * file distributed with this source distribution.
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA
 *
 * $URL$
 * $Id$
 */

#include "graphics/line2d.h"
#include "graphics/rect2d.h"

namespace Graphics {

Line2d::Line2d() :
	_a(0), _b(0), _c(0) {

}

Line2d::Line2d(const Vector2d &direction, const Vector2d &point) {
	Vector2d d = direction;
	_a = d._y / d._x;
	_b = -1;

	if (_b == 0) {
		_c = -point._x;
	} else {
		_c = point._y - (d._y / d._x) * point._x;
	}
}

Line2d Line2d::getPerpendicular(const Vector2d &point) const {
	Vector2d v(1, _b / _a);

	return Line2d(v, point);
}

Vector2d Line2d::getDirection() const {
	return Vector2d(1, _a);
}

bool Line2d::intersectsLine(const Line2d &line, Vector2d *pos) const {
	// 	if (*this == line) {
	// 		return false;
	// 	}

	float a = _a;
	float b = _b;
	float c = _c;

	float d = line._a;
	float e = line._b;
	float f = line._c;

	float x, y;

	if (d * b - a * e == 0 || a == 0) {
		return false;
	}

	if (!pos) {
		return true;
	}

	/*
	 * {ax + by + c = 0 -> x = -(by + c) / a
	 * {dx + ey + f = 0 -> y = (-dc + af) / (db - ae)
	 */

	y = (-d * c + a * f) / (d * b - a * e);
	x = -(b * y + c) / a;

	*pos = Vector2d(x, y);
	return true;
}

bool Line2d::containsPoint(const Vector2d &point) const {
	float n = _a * point._x + _b * point._y + _c;
	return (n < 0.0001 && n > -0.0001);
}

float Line2d::getYatX(float x) const {
	return -(_a * x + _c) / _b;
}




Segment2d::Segment2d() {

}

Segment2d::Segment2d(const Vector2d &b, const Vector2d &e) :
	_begin(b), _end(e) {

}

Segment2d::Segment2d(const Segment2d &other) {
	*this = other;
}

Vector2d Segment2d::begin() const {
	return _begin;
}

Vector2d Segment2d::end() const {
	return _end;
}

Vector2d Segment2d::middle() const {
	return (_begin + _end) / 2.f;
}

Line2d Segment2d::getLine() const {
	float y = _end._y - _begin._y;
	float x = _end._x - _begin._x;
	Vector2d v(x, y);

	return Line2d(v, _begin);
}

Line2d Segment2d::getPerpendicular(const Vector2d &point) const {
	return getLine().getPerpendicular(point);
}

bool Segment2d::intersectsSegment(const Segment2d &other, Vector2d *pos) {
	float denom = ((other._end._y - other._begin._y) * (_end._x - _begin._x)) -
	((other._end._x - other._begin._x) * (_end._y - _begin._y));


	float d = ((_end._y - _begin._y) * (other._end._x - other._begin._x)) -
	((_end._x - _begin._x) * (other._end._y - other._begin._y));

	float nume_a = ((other._end._x - other._begin._x) * (_begin._y - other._begin._y)) -
	((other._end._y - other._begin._y) * (_begin._x - other._begin._x));

	float nume_b = ((_end._x - _begin._x) * (other._begin._y - _begin._y)) -
	((_end._y - _begin._y) * (other._begin._x - _begin._x));

	if (denom == 0.0f) {
		return false;
	}

	float ua = nume_a / denom;
	float ub = nume_b / d;

	if (ua < 0 || ua > 1 || ub < 0 || ub > 1) {
		return false;
	}

	// Get the intersection point.
	if (pos)
		*pos = _begin + (_end - _begin) * ua;

	return true;
}

bool Segment2d::intersectsLine(const Line2d &line, Vector2d *pos) {
	Vector2d p;
	if (getLine().intersectsLine(line, &p) && containsPoint(p)) {
		if (pos)
			*pos = p;
		return true;
	}

	return false;
}

bool Segment2d::containsPoint(const Vector2d &point) const {
	if (getLine().containsPoint(point)) {
		return Rect2d(_begin, _end).containsPoint(point);
	}

	return false;
}

void Segment2d::operator=(const Segment2d &other) {
	_begin = other._begin;
	_end = other._end;
}

}