Check if a vertex is in triangle using barycentric coordinates computation. - Java java.lang

Java examples for java.lang:Math Vector

  1. HOME
  2. Java
  3. java.lang
  4. Math Vector

Description

Check if a vertex is in triangle using barycentric coordinates computation.

Demo Code

/**/*from ww  w.  j a  v a 2 s  .  c  om*/
 * 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
 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
 * 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
 * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * The views and conclusions contained in the software and documentation are those of the
 * authors and should not be interpreted as representing official policies, either expressed
 * or implied, of JogAmp Community.
 */
//package com.java2s;

public class Main {
    /**
     * Check if a vertex is in triangle using
     * barycentric coordinates computation.
     * @param a first triangle vertex
     * @param b second triangle vertex
     * @param c third triangle vertex
     * @param p the vertex in question
     * @return true if p is in triangle (a, b, c), false otherwise.
     */
    public static boolean isInTriangleVec3(final float[] a,
            final float[] b, final float[] c, final float[] p,
            final float[] ac, final float[] ab, final float[] ap) {
        // Compute vectors
        subVec3(ac, c, a); //v0
        subVec3(ab, b, a); //v1
        subVec3(ap, p, a); //v2

        // Compute dot products
        final float dotAC_AC = dotVec3(ac, ac);
        final float dotAC_AB = dotVec3(ac, ab);
        final float dotAB_AB = dotVec3(ab, ab);
        final float dotAC_AP = dotVec3(ac, ap);
        final float dotAB_AP = dotVec3(ab, ap);

        // Compute barycentric coordinates
        final float invDenom = 1 / (dotAC_AC * dotAB_AB - dotAC_AB
                * dotAC_AB);
        final float u = (dotAB_AB * dotAC_AP - dotAC_AB * dotAB_AP)
                * invDenom;
        final float v = (dotAC_AC * dotAB_AP - dotAC_AB * dotAC_AP)
                * invDenom;

        // Check if point is in triangle
        return (u >= 0) && (v >= 0) && (u + v < 1);
    }

    /**
     * Subtracts two vectors, result = v1 - v2
     * @param result float[3] result vector, may be either v1 or v2 (in-place)
     * @param v1 vector 1
     * @param v2 vector 2
     * @return result vector for chaining
     */
    public static float[] subVec3(final float[] result, final float[] v1,
            final float[] v2) {
        result[0] = v1[0] - v2[0];
        result[1] = v1[1] - v2[1];
        result[2] = v1[2] - v2[2];
        return result;
    }

    /**
     * Return the dot product of two points
     * @param vec1 vector 1
     * @param vec2 vector 2
     * @return the dot product as float
     */
    public static float dotVec3(final float[] vec1, final float[] vec2) {
        return vec1[0] * vec2[0] + vec1[1] * vec2[1] + vec1[2] * vec2[2];
    }
}

Related Tutorials