302 lines
8.2 KiB
C
302 lines
8.2 KiB
C
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/*
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----
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This file is part of SECONDO.
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Copyright (C) 2004, University in Hagen, Department of Computer Science,
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Database Systems for New Applications.
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SECONDO is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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SECONDO is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with SECONDO; if not, write to the Free Software
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Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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----
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//paragraph [1] Title: [{\Large \bf \begin {center}] [\end {center}}]
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//[TOC] [\tableofcontents]
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//[_] [\_]
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[1] Header File for the class ~LineIntersection~
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[TOC]
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1 Overview
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This header file contains the class ~LineIntersection~.
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This class detects intersections between two line segments.
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1 Defines and includes
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*/
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#pragma once
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#include <stdlib.h>
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#include "InternalGeometries.h"
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#include "Rational.h"
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namespace RobustPlaneSweep
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{
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/*
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1 Class ~LineIntersection~
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*/
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class LineIntersection
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{
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private:
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/*
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1.1 ~IsPointOnLineHelper~
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*/
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static bool IsPointOnLineHelper(long long p,
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long long s0,
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long long s1,
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bool includePseudoIntersections)
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{
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if (includePseudoIntersections) {
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if ((p >= s0 && p <= s1) || (p >= s1 && p <= s0)) {
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return true;
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}
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} else {
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if ((p > s0 && p < s1) || (p > s1 && p < s0)) {
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return true;
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}
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}
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return false;
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}
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public:
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/*
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1.1 ~GetIntersections~
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Determines if the segments with the end points a0-a1 and b0-b1 have any
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intersections. Returns 0 if there is none,
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1 if there is one (not necessarily proper) intersection and
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2 if there is the segments overlap.
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if ~includePseudoIntersections~ is false, then only intersection points are
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returned that split at least one segment into two pieces.
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if ~includeCompleteOverlaps~ is false, then overlapping segments where
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both segments have equal end points are returned as zero intersection points.
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*/
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static int GetIntersections(const InternalPoint& a0,
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const InternalPoint& a1,
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const InternalPoint& b0,
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const InternalPoint& b1,
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const bool includePseudoIntersections,
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const bool includeCompleteOverlaps,
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InternalIntersectionPoint &i0,
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InternalIntersectionPoint &i1)
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{
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long long ax = (a1.GetX() - a0.GetX());
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long long ay = (a1.GetY() - a0.GetY());
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long long bx = (b1.GetX() - b0.GetX());
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long long by = (b1.GetY() - b0.GetY());
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long long abx = (a0.GetX() - b0.GetX());
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long long aby = (a0.GetY() - b0.GetY());
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long long denominator = bx * ay - by * ax;
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if (denominator == 0) {
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if ((bx * aby - by * abx) != 0 || (ax * aby - ay * abx) != 0) {
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return 0;
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}
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bool aIsPoint = (ax == 0 && ay == 0);
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bool bIsPoint = (bx == 0 && by == 0);
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if (aIsPoint && bIsPoint) {
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if (abx == 0 && aby == 0) {
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i0 = InternalIntersectionPoint(a0);
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return 1;
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} else {
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return 0;
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}
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} else if (aIsPoint) {
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if (llabs(bx) > llabs(by)) {
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if (!IsPointOnLineHelper(a0.GetX(),
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b0.GetX(),
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b1.GetX(),
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includePseudoIntersections)) {
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return 0;
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}
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} else {
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if (!IsPointOnLineHelper(a0.GetY(),
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b0.GetY(),
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b1.GetY(),
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includePseudoIntersections)) {
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return 0;
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}
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}
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i0 = InternalIntersectionPoint(a0);
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return 1;
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} else if (bIsPoint) {
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if (llabs(ax) > llabs(ay)) {
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if (!IsPointOnLineHelper(b0.GetX(),
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a0.GetX(),
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a1.GetX(),
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includePseudoIntersections)) {
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return 0;
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}
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} else {
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if (!IsPointOnLineHelper(b0.GetY(),
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a0.GetY(),
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a1.GetY(),
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includePseudoIntersections)) {
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return 0;
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}
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}
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i0 = InternalIntersectionPoint(b0);
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return 1;
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} else {
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SimpleRational t0(0, 1), t1(0, 1);
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if (llabs(bx) > llabs(by)) {
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t0 = SimpleRational(abx, bx);
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t1 = SimpleRational(a1.GetX() - b0.GetX(), bx);
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} else {
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t0 = SimpleRational(aby, by);
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t1 = SimpleRational(a1.GetY() - b0.GetY(), by);
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}
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if (t0 > t1) {
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SimpleRational temp = t0;
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t0 = t1;
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t1 = temp;
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}
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if (t1 < 0 || t0 > 1) {
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return 0;
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}
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if (t0 < 0) {
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t0 = SimpleRational(0, 1);
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}
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if (t1 > 1) {
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t1 = SimpleRational(1, 1);
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}
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if (t1 == 0) {
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// touches only at start point
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if (!includePseudoIntersections) {
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return 0;
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}
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i0 = InternalIntersectionPoint(b0);
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return 1;
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} else if (t0 == 1) {
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// touches only at end point
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if (!includePseudoIntersections) {
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return 0;
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}
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i0 = InternalIntersectionPoint(b1);
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return 1;
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} else if (t0 == 0 && t1 == 1) {
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if (!includeCompleteOverlaps) {
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if (a0.GetX() == b0.GetX() && a0.GetY() == b0.GetY()
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&& a1.GetX() == b1.GetX()
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&& a1.GetY() == b1.GetY()) {
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return 0;
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}
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if (a0.GetX() == b1.GetX() && a0.GetY() == b1.GetY()
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&& a1.GetX() == b0.GetX()
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&& a1.GetY() == b0.GetY()) {
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return 0;
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}
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}
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i0 = InternalIntersectionPoint(b0);
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i1 = InternalIntersectionPoint(b1);
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return 2;
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} else if (t0 == t1) {
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Rational ratt0 = (Rational)t0;
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i0 = InternalIntersectionPoint((ratt0 * (int)bx + b0.GetX()),
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(ratt0 * (int)by + b0.GetY()));
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return 1;
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} else {
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Rational ratt0 = (Rational)t0;
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Rational ratt1 = (Rational)t1;
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i0 = InternalIntersectionPoint((ratt0 * (int)bx + b0.GetX()),
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(ratt0 * (int)by + b0.GetY()));
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i1 = InternalIntersectionPoint((ratt1 * (int)bx + b0.GetX()),
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(ratt1 * (int)by + b0.GetY()));
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return 2;
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}
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}
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} else {
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SimpleRational si((by * abx - bx * aby), denominator);
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if (si < 0 || si > 1) {
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return 0;
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}
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SimpleRational ti((ax * aby - ay * abx), -denominator);
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if (ti < 0 || ti > 1) {
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return 0;
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}
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if (si == 0) {
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if (!includePseudoIntersections && (ti == 0 || ti == 1)) {
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return 0;
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}
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i0 = InternalIntersectionPoint(a0);
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return 1;
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}
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if (si == 1) {
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if (!includePseudoIntersections && (ti == 0 || ti == 1)) {
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return 0;
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}
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i0 = InternalIntersectionPoint(a1);
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return 1;
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}
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if (ti == 0) {
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if (!includePseudoIntersections && (si == 0 || si == 1)) {
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return 0;
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}
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i0 = InternalIntersectionPoint(b0);
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return 1;
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}
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if (ti == 1) {
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if (!includePseudoIntersections && (si == 0 || si == 1)) {
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return 0;
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}
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i0 = InternalIntersectionPoint(b1);
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return 1;
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}
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Rational ratSi = (Rational)si;
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Rational ix = (ratSi * (int)ax + a0.GetX());
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Rational iy = (ratSi * (int)ay + a0.GetY());
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i0 = InternalIntersectionPoint(ix, iy);
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return 1;
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}
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}
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};
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}
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