Mercurial > dive4elements > river
view flys-artifacts/src/main/java/de/intevation/flys/artifacts/geom/VectorUtils.java @ 1975:b30e1710df1d
Server-side of interactive cross-section diagrams.
flys-artifacts/trunk@3394 c6561f87-3c4e-4783-a992-168aeb5c3f6f
author | Felix Wolfsteller <felix.wolfsteller@intevation.de> |
---|---|
date | Tue, 13 Dec 2011 09:10:48 +0000 |
parents | 6f83d9d434f2 |
children | 5642a83420f2 |
line wrap: on
line source
package de.intevation.flys.geom; import java.awt.geom.Point2D; public final class VectorUtils { public static final double EPSILON = 1e-4; private VectorUtils() { } public static final double X(Point2D p) { return p.getX(); } public static final double Y(Point2D p) { return p.getY(); } public static final Point2D sub(Point2D a, Point2D b) { return new Point2D.Double(X(a)-X(b), Y(a)-Y(b)); } public static final double dot(Point2D a, Point2D b) { return X(a)*X(b) + Y(a)*Y(b); } public static final Point2D add(Point2D a, Point2D b) { return new Point2D.Double(X(a)+X(b), Y(a)+Y(b)); } public static final Point2D negate(Point2D a) { return new Point2D.Double(-X(a), -Y(a)); } public static final Point2D ortho(Point2D a) { return new Point2D.Double(-Y(a), X(a)); } public static final Point2D scale(Point2D a, double s) { return new Point2D.Double(s*X(a), s*Y(a)); } public static final double lengthSq(Point2D a) { double x = X(a); double y = Y(a); return x*x + y*y; } public static final double length(Point2D a) { return Math.sqrt(lengthSq(a)); } public static final Point2D normalize(Point2D a) { double length = length(a); return length != 0d ? scale(a, 1d/length) : new Point2D.Double(X(a), Y(a)); } public static final double L1(Point2D a, Point2D b) { return Math.abs(X(a)-X(b)) + Math.abs(Y(a)-Y(b)); } public static final boolean collinear(Point2D a, Point2D b, Point2D c) { double x1 = X(a); double y1 = Y(a); double x2 = X(b); double y2 = Y(b); double x3 = X(c); double y3 = Y(c); return Math.abs((x2-x1)*(y3-y1)-(y2-y1)*(x3-x1)) < EPSILON; } public static boolean epsilonEquals(Point2D a, Point2D b) { return Math.abs(X(a)-X(b)) < EPSILON && Math.abs(Y(a)-Y(b)) < EPSILON; } public static final Point2D intersection( Point2D p1, Point2D p2, Point2D p3, Point2D p4 ) { double x1 = X(p1); double y1 = Y(p1); double x2 = X(p2); double y2 = Y(p2); double x3 = X(p3); double y3 = Y(p3); double x4 = X(p4); double y4 = Y(p4); // Compute a1, b1, c1, where line joining points 1 and 2 // is "a1 x + b1 y + c1 = 0". double a1 = y2 - y1; double b1 = x1 - x2; double c1 = x2*y1 - x1*y2; // Compute r3 and r4. double r3 = a1*x3 + b1*y3 + c1; double r4 = a1*x4 + b1*y4 + c1; if (r3 != 0d && r4 != 0d && r3*r4 >= 0) { return null; } // Compute a2, b2, c2 double a2 = y4 - y3; double b2 = x3 - x4; double c2 = (x4 * y3) - (x3 * y4); // Compute r1 and r2 double r1 = a2*x1 + b2*y1 + c2; double r2 = a2*x2 + b2*y2 + c2; if (r1 != 0d && r2 != 0d && r1*r2 >= 0) { return null; } // Line segments intersect: compute intersection point. double denom = a1*b2 - a2*b1; if (denom == 0d) { // collinear return null; } double offset = Math.abs(denom)/2d; // The denom/2 is to get rounding instead of truncating. It // is added or subtracted to the numerator, depending upon the // sign of the numerator. double num = b1*c2 - b2*c1; double x = num < 0d ? (num - offset)/denom : (num + offset)/denom; num = a2*c1 - a1*c2; double y = num < 0d ? (num - offset)/denom : (num + offset)/denom; return new Point2D.Double(x, y); } } // vim:set ts=4 sw=4 si et sta sts=4 fenc=utf8 :