/*
* Copyright (C) 2011-2015, Peter Abeles. All Rights Reserved.
*
* This file is part of Geometric Regression Library (GeoRegression).
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package georegression.metric;
import georegression.struct.line.LineGeneral2D_F32;
import georegression.struct.line.LineParametric2D_F32;
import georegression.struct.line.LineSegment2D_F32;
import georegression.struct.point.Point2D_F32;
import georegression.struct.point.Point3D_F32;
import georegression.struct.shapes.Polygon2D_F32;
import georegression.struct.shapes.Quadrilateral_F32;
import georegression.struct.shapes.Rectangle2D_F32;
import georegression.struct.shapes.RectangleLength2D_F32;
/**
* Functions relating to finding the points at which two shapes intersect with each other.
*
* @author Peter Abeles
*/
public class Intersection2D_F32 {
// todo comment
// todo how are parallel lines handled?
/**
*
* Checks to see if the point is contained inside the convex polygon. If the
* point is an the polygon's perimeter it is considered to NOT be inside.
*
*
*
* Clockwise or counter-clockwise order of the polygon does not matter.
*
*
* @param polygon Convex polygon. Not modified.
* @param pt Point. Not modified.
* @return True if the point is contained inside the polygon.
*/
// Ported from internet code 12/2011
// http://www.ecse.rpi.edu/Homepages/wrf/Research/Short_Notes/pnpoly.html
public static boolean containConvex( Polygon2D_F32 polygon , Point2D_F32 pt )
{
final int N = polygon.size();
boolean c = false;
for (int i = 0, j = N-1; i < N; j = i++) {
Point2D_F32 a = polygon.vertexes.data[i];
Point2D_F32 b = polygon.vertexes.data[j];
if ( ((a.y>pt.y) != (b.y>pt.y)) && (pt.x < (b.x-a.x) * (pt.y-a.y) / (b.y-a.y) + a.x) )
c = !c;
}
return c;
}
/**
* Checks to see if the point is contained inside the concave polygon.
*
* NOTE: Points which lie along the perimeter may or may not be considered as inside
*
* @param polygon Convex polygon. Not modified.
* @param pt Point. Not modified.
* @return True if the point is contained inside the polygon.
*/
public static boolean containConcave( Polygon2D_F32 polygon , Point2D_F32 pt )
{
final int N = polygon.size();
int left=0;
int right=0;
for (int i = 0; i < N-1; i++) {
Point2D_F32 a = polygon.vertexes.data[i];
Point2D_F32 b = polygon.vertexes.data[i+1];
if( (pt.y >= a.y && pt.y < b.y) || (pt.y >= b.y && pt.y < a.y) ) {
// location of line segment along x-axis at y = pt.y
float x = b.y==a.y ? pt.x : (pt.y-a.y)*(b.x-a.x)/(b.y-a.y) + a.x;
if( x <= pt.x )
left++;
else if( x > pt.x )
right++;
}
}
Point2D_F32 a = polygon.vertexes.data[N-1];
Point2D_F32 b = polygon.vertexes.data[0];
if( (pt.y >= a.y && pt.y < b.y) || (pt.y >= b.y && pt.y < a.y) ) {
// location of line segment along x-axis at y = pt.y
float x = b.y==a.y ? pt.x : (pt.y-pt.y)*(b.x-a.x)/(b.y-a.y) + a.x;
if( x <= pt.x )
left++;
else if( x > pt.x )
right++;
}
return (left % 2 == 1 && right % 2 == 1);
}
/**
* True if the point is contained inside the quadrilateral.
*
* @param quad quadrilateral
* @param pt point
* @return true if the point is inside and false if it is not.
*/
public static boolean contains( Quadrilateral_F32 quad , Point2D_F32 pt ) {
return containTriangle(quad.a, quad.b, quad.d, pt) ||
containTriangle(quad.b, quad.c, quad.d, pt);
}
/**
* Returns true of the the point is inside the triangle.
*
* This function is simply an unrolled version of {@link #containConcave(Polygon2D_F32, Point2D_F32)}.
*
* @param a vertex in triangle
* @param b vertex in triangle
* @param c vertex in triangle
* @param pt Point which is being tested for containment inside of triangle
* @return true if the point is inside of triangle
*/
public static boolean containTriangle( Point2D_F32 a , Point2D_F32 b , Point2D_F32 c , Point2D_F32 pt )
{
boolean ret = false;
if ( ((a.y>pt.y) != (b.y>pt.y)) && (pt.x < (b.x-a.x) * (pt.y-a.y) / (b.y-a.y) + a.x) )
ret = true;
if ( ((b.y>pt.y) != (c.y>pt.y)) && (pt.x < (c.x-b.x) * (pt.y-b.y) / (c.y-b.y) + b.x) )
ret = !ret;
if ( ((c.y>pt.y) != (a.y>pt.y)) && (pt.x < (a.x-c.x) * (pt.y-c.y) / (a.y-c.y) + c.x) )
ret = !ret;
return ret;
}
/**
* Finds the point of intersection between two lines and returns the point.
*
* @param a Line.
* @param b Line.
* @param ret storage for the point of intersection. If null a new point will be declared.
* @return If the two lines intersect it returns the point of intersection. null if they don't intersect or have infinite intersections.
*/
public static Point2D_F32 intersection( LineParametric2D_F32 a, LineParametric2D_F32 b , Point2D_F32 ret ) {
float t_b = a.getSlopeX() * ( b.getY() - a.getY() ) - a.getSlopeY() * ( b.getX() - a.getX() );
float bottom = a.getSlopeY() * b.getSlopeX() - b.getSlopeY() * a.getSlopeX();
if( bottom == 0 )
return null;
t_b /= bottom;
float x = b.getSlopeX() * t_b + b.getX();
float y = b.getSlopeY() * t_b + b.getY();
if( ret == null )
ret = new Point2D_F32();
ret.set(x,y);
return ret;
}
/**
* Finds the point of intersection between two lines. The point of intersection is specified as a point along
* the parametric line 'a'. (x,y) = (x_0,y_0) + t*(slope_x,slope_y), where 't' is the location returned.
*
* @param a Line.
* @param b Line.
* @return The location along 'target'. If the lines do not intersect or have infinite intersections Float.NaN is returned.
*/
public static float intersection( LineParametric2D_F32 a, LineParametric2D_F32 b ) {
float t_a = b.getSlopeX() * ( a.getY() - b.getY() ) - b.getSlopeY() * ( a.getX() - b.getX() );
float bottom = b.getSlopeY() * a.getSlopeX() - a.getSlopeY() * b.getSlopeX();
if( bottom == 0 )
return Float.NaN;
return t_a/bottom;
}
/**
* Finds the point of intersection between two lines segments.
*
* @param l_0 Line segment.
* @param l_1 line segment.
* @param ret storage for the point of intersection. If null a new point will be declared.
* @return If the two lines intersect it returns the point of intersection. null if they don't intersect or have infinite intersections.
*/
public static Point2D_F32 intersection( LineSegment2D_F32 l_0, LineSegment2D_F32 l_1,
Point2D_F32 ret ) {
float a0 = l_0.b.x - l_0.a.x;
float b0 = l_0.b.y - l_0.a.y;
float a1 = l_1.b.x - l_1.a.x;
float b1 = l_1.b.y - l_1.a.y;
float top = b0 * ( l_1.a.x - l_0.a.x ) + a0 * ( l_0.a.y - l_1.a.y );
float bottom = a0 * b1 - b0 * a1;
if( bottom == 0 )
return null;
float t_1 = top / bottom;
// does not intersect along the second line segment
if( t_1 < 0 || t_1 > 1 )
return null;
top = b1 * ( l_0.a.x - l_1.a.x ) + a1 * ( l_1.a.y - l_0.a.y );
bottom = a1 * b0 - b1 * a0;
float t_0 = top / bottom;
// does not intersect along the first line segment
if( t_0 < 0 || t_0 > 1 )
return null;
if( ret == null ) {
ret = new Point2D_F32();
}
ret.set( l_1.a.x + a1 * t_1, l_1.a.y + b1 * t_1 );
return ret;
}
/**
*
* Finds the intersection of two lines as a 2D point in homogeneous coordinates. Because the
* solution is found in homogeneous coordinates it can even handle parallel lines which "intersect
* at infinity".
*
*
*
* A 2D point in homogeneous coordinates is expressed as the triple (x,y,z), which can be converted
* into the standard notation as x' = x/z and y'= y/z. If the lines are parallel and intersect at
* infinity then z=0 and the above conversion will fail.
*
*
* @param a Line
* @param b Line
* @param ret Storage for point of intersection.
* @return Point of intersection represented in homogeneous coordinates.
*/
public static Point3D_F32 intersection( LineGeneral2D_F32 a , LineGeneral2D_F32 b , Point3D_F32 ret )
{
if( ret == null )
ret = new Point3D_F32();
// compute the intersection as the cross product of 'a' and 'b'
ret.x = a.B * b.C - a.C * b.B;
ret.y = a.C * b.A - a.A * b.C;
ret.z = a.A * b.B - a.B * b.A;
return ret;
}
/**
*
* Finds the intersection of two lines as a 2D point in coordinates. If the lines are parallel
* then null is returned.
*
*
* @param a Line
* @param b Line
* @param ret Storage for point of intersection.
* @return Point of intersection in 2D coordinates. null if intersection at infinity
*/
public static Point2D_F32 intersection( LineGeneral2D_F32 a , LineGeneral2D_F32 b , Point2D_F32 ret )
{
if( ret == null )
ret = new Point2D_F32();
// compute the intersection as the cross product of 'a' and 'b'
ret.x = a.B * b.C - a.C * b.B;
ret.y = a.C * b.A - a.A * b.C;
float z = a.A * b.B - a.B * b.A;
if( z == 0 )
return null;
ret.x /= z;
ret.y /= z;
return ret;
}
/**
* Finds the point of intersection between a line and a line segment. The point of intersection
* is specified as the distance along the parametric line. If no intersection is found then
* Float.NaN is returned.
*
* @param target A line whose location along which the point of intersection is being found. Not modified.
* @param l Line segment which is being tested for intersection. Not modified.
* @return The location along 'target'. If the lines do not intersect or have infinite intersections Float.NaN is returned.
*/
public static float intersection( LineParametric2D_F32 target, LineSegment2D_F32 l ) {
float a1 = l.b.x - l.a.x;
float b1 = l.b.y - l.a.y;
float top = target.slope.y * ( l.a.x - target.p.x ) + target.slope.x * ( target.p.y - l.a.y );
float bottom = target.slope.x * b1 - target.slope.y * a1;
if( bottom == 0 )
return Float.NaN;
float t_1 = top / bottom;
// does not intersect along the second line segment
if( t_1 < 0 || t_1 > 1 )
return Float.NaN;
top = b1 * ( target.p.x - l.a.x ) + a1 * ( l.a.y - target.p.y );
bottom = a1 * target.slope.y - b1 * target.slope.x;
return top / bottom;
}
/**
*
* Checks to see if the specified point is inside the rectangle. A point is inside
* if it is ≥ the lower extend and < the upper extent.
*
*
* inside = x ≥ x0 AND x < x0+width AND y ≥ y0 AND y < y0+height
*
* @param a Rectangle.
* @param x x-coordinate of point being tested for containment
* @param y y-coordinate of point being tested for containment
* @return true if inside and false if output
*/
public static boolean contains( RectangleLength2D_F32 a, float x, float y ) {
if( a.getX() <= x && a.getX() + a.getWidth() > x ) {
return a.getY() <= y && a.getY() + a.getHeight() > y;
}
return false;
}
/**
*
* Checks to see if the specified point is inside the rectangle. A point is inside
* if it is ≥ the lower extend and ≤ the upper extent.
*
*
* {@code inside = x ≥ x0 AND x ≤ x0+width and y ≥ y0 AND y ≤ y0+height}
*
* @param a Rectangle.
* @param x x-coordinate of point being tested for containment
* @param y y-coordinate of point being tested for containment
* @return true if inside and false if output
*/
public static boolean contains2( RectangleLength2D_F32 a, float x, float y ) {
if( a.getX() <= x && a.getX() + a.getWidth() >= x ) {
return a.getY() <= y && a.getY() + a.getHeight() >= y;
}
return false;
}
/**
*
* Checks to see if the specified point is inside the rectangle. A point is inside
* if it is ≥ the lower extend and < the upper extent.
*
*
* inside = x ≥ x0 AND x ≤ x1 AND y ≥ y0 AND y ≤ y1
*
* @param a Rectangle.
* @param x x-coordinate of point being tested for containment
* @param y y-coordinate of point being tested for containment
* @return true if inside and false if output
*/
public static boolean contains( Rectangle2D_F32 a, float x, float y ) {
return( a.p0.x <= x && a.p1.x > x && a.p0.y <= y && a.p1.y > y );
}
/**
*
* Checks to see if the specified point is inside the rectangle. A point is inside
* if it is ≥ the lower extend and ≤ the upper extent.
*
*
* inside = x ≥ x0 AND x ≤ x1 AND y ≥ y0 AND y ≤ y1
*
* @param a Rectangle.
* @param x x-coordinate of point being tested for containment
* @param y y-coordinate of point being tested for containment
* @return true if inside and false if output
*/
public static boolean contains2( Rectangle2D_F32 a, float x, float y ) {
return( a.p0.x <= x && a.p1.x >= x && a.p0.y <= y && a.p1.y >= y );
}
public static RectangleLength2D_F32 intersection( RectangleLength2D_F32 a, RectangleLength2D_F32 b ) {
float tl_x, tl_y, w, h;
if( a.getX() >= b.getX() ) {
if( a.getX() >= b.getX() + b.getWidth() )
return null;
tl_x = a.getX();
w = b.getX() + b.getWidth() - a.getX();
} else {
if( a.getX() + a.getWidth() <= b.getX() )
return null;
tl_x = b.getX();
w = a.getX() + a.getWidth() - b.getX();
}
if( a.getY() >= b.getY() ) {
if( a.getY() >= b.getY() + b.getHeight() )
return null;
tl_y = a.getY();
h = b.getY() + b.getHeight() - a.getY();
} else {
if( a.getY() + a.getHeight() <= b.getY() )
return null;
tl_y = b.getY();
h = a.getY() + a.getHeight() - b.getY();
}
return new RectangleLength2D_F32( tl_x, tl_y, w, h );
}
/**
* Checks to see if the two rectangles intersect each other
*
* @param a Rectangle
* @param b Rectangle
* @return true if intersection
*/
public static boolean intersects( Rectangle2D_F32 a , Rectangle2D_F32 b ) {
return( a.p0.x < b.p1.x && a.p1.x > b.p0.x && a.p0.y < b.p1.y && a.p1.y > b.p0.y );
}
/**
* Finds the intersection between two rectangles. If the rectangles don't intersect then false is returned.
*
* @param a Rectangle
* @param b Rectangle
* @param result Storage for the found intersection
* @return true if intersection
*/
public static boolean intersection( Rectangle2D_F32 a , Rectangle2D_F32 b , Rectangle2D_F32 result ) {
if( !intersects(a,b) )
return false;
result.p0.x = (float)Math.max(a.p0.x,b.p0.x);
result.p1.x = (float)Math.min(a.p1.x,b.p1.x);
result.p0.y = (float)Math.max(a.p0.y,b.p0.y);
result.p1.y = (float)Math.min(a.p1.y,b.p1.y);
return true;
}
/**
* Returns the area of the intersection of two rectangles.
*
* @param a Rectangle
* @param b Rectangle
* @return area of intersection
*/
public static float intersectionArea( Rectangle2D_F32 a , Rectangle2D_F32 b ) {
if( !intersects(a,b) )
return 0;
float x0 = (float)Math.max(a.p0.x,b.p0.x);
float x1 = (float)Math.min(a.p1.x,b.p1.x);
float y0 = (float)Math.max(a.p0.y,b.p0.y);
float y1 = (float)Math.min(a.p1.y,b.p1.y);
return (x1-x0)*(y1-y0);
}
}
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