Compute the winding of given points - Java java.lang

Java examples for java.lang:Math Vector

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Description

Compute the winding of given points

Demo Code

/**/*from w ww  . ja  va 2  s . c  o  m*/
 * Copyright 2010 JogAmp Community. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without modification, are
 * permitted provided that the following conditions are met:
 *
 *    1. Redistributions of source code must retain the above copyright notice, this list of
 *       conditions and the following disclaimer.
 *
 *    2. Redistributions in binary form must reproduce the above copyright notice, this list
 *       of conditions and the following disclaimer in the documentation and/or other materials
 *       provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY JogAmp Community ``AS IS'' AND ANY EXPRESS OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
 * FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL JogAmp Community OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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 * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
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 */
import java.util.ArrayList;

public class Main{
    /** Compute the winding of given points
     * @param a first vertex
     * @param b second vertex
     * @param c third vertex
     * @return Winding
     */
    public static Winding getWinding(final Vert2fImmutable a,
            final Vert2fImmutable b, final Vert2fImmutable c) {
        return triAreaVec2(a, b, c) > 0 ? Winding.CCW : Winding.CW;
    }
    /** Compute the  general winding of the vertices
     * @param vertices array of Vertices
     * @return CCW or CW {@link Winding}
     */
    public static Winding getWinding(
            final ArrayList<? extends Vert2fImmutable> vertices) {
        return area(vertices) >= 0 ? Winding.CCW : Winding.CW;
    }
    /**
     * Computes oriented area of a triangle
     * @param a first vertex
     * @param b second vertex
     * @param c third vertex
     * @return compute twice the area of the oriented triangle (a,b,c), the area
     * is positive if the triangle is oriented counterclockwise.
     */
    public static float triAreaVec2(final Vert2fImmutable a,
            final Vert2fImmutable b, final Vert2fImmutable c) {
        final float[] A = a.getCoord();
        final float[] B = b.getCoord();
        final float[] C = c.getCoord();
        return (B[0] - A[0]) * (C[1] - A[1]) - (B[1] - A[1])
                * (C[0] - A[0]);
    }
    /**
     * Computes oriented area of a triangle
     * @param A first vertex
     * @param B second vertex
     * @param C third vertex
     * @return compute twice the area of the oriented triangle (a,b,c), the area
     * is positive if the triangle is oriented counterclockwise.
     */
    public static float triAreaVec2(final float[] A, final float[] B,
            final float[] C) {
        return (B[0] - A[0]) * (C[1] - A[1]) - (B[1] - A[1])
                * (C[0] - A[0]);
    }
    /** Computes the area of a list of vertices to check if ccw
     * @param vertices
     * @return positive area if ccw else negative area value
     */
    public static float area(
            final ArrayList<? extends Vert2fImmutable> vertices) {
        final int n = vertices.size();
        float area = 0.0f;
        for (int p = n - 1, q = 0; q < n; p = q++) {
            final float[] pCoord = vertices.get(p).getCoord();
            final float[] qCoord = vertices.get(q).getCoord();
            area += pCoord[0] * qCoord[1] - qCoord[0] * pCoord[1];
        }
        return area;
    }
}

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