/*
 * pVector.java
 *
 * (C) 2005, Alex S.
 */

import java.util.*;
import java.awt.*;

/**
 * basic vector routines.
 */
public class pVector {

    /**
     * given 2 points, find their sum
     */
    public static void vectorAdd (double[] va, double[] vb, double[] out){
        out[0] = va[0]+vb[0];
        out[1] = va[1]+vb[1];
        out[2] = va[2]+vb[2];
    }

    /**
     * given 2 points, find their difference
     */
    public static void vectorSubtract (double[] va, double[] vb, double[] out){
        out[0] = va[0]-vb[0];
        out[1] = va[1]-vb[1];
        out[2] = va[2]-vb[2];
    }

    /**
     * cross product of two vectors
     */
    public static void crossProduct(double[] v1, double[] v2, double[] cross ) {
        cross[0] = v1[1]*v2[2] - v1[2]*v2[1];
        cross[1] = v1[2]*v2[0] - v1[0]*v2[2];
        cross[2] = v1[0]*v2[1] - v1[1]*v2[0];
    }

    /**
     * given 2 points, find their sum
     */
    public static void vectorScale (double[] v, double s, double[] out){
        out[0] = v[0]*s;
        out[1] = v[1]*s;
        out[2] = v[2]*s;
    }

    /**
     * normalize
     */
    public static double vectorNormalize(double[] in, double[] out ) {
        double  length, ilength;
        length = (double)Math.sqrt(in[0]*in[0] + in[1]*in[1] + in[2]*in[2]);
        if (length == 0) {
            return 0;
        }
        ilength = (double)1.0/length;
        out[0] = in[0]*ilength;
        out[1] = in[1]*ilength;
        out[2] = in[2]*ilength;
        return length;
    }   

    /**
     * dot product
     */
    public static double dotProduct (double[] v1, double[] v2){
        return v1[0]*v2[0] + v1[1]*v2[1] + v1[2]*v2[2];
    }

    /**
     * gets plane equation from three points on plane
     * 
     * Plane is: Ax + By + Cx + D = 0
     */
    public static boolean planeFromPoints(double[] plane, 
            double[] a, double[] b,double[] c,double[] d ){

        double[] d1 = new double[4];
        double[] d2 = new double[4];

        vectorSubtract( b, a, d1 );
        if (dotProduct(d1,d1) < (double)0.02) {
            vectorSubtract( c, a, d1 );
            vectorSubtract( d, a, d2 );
        } else {
            vectorSubtract( c, a, d2 );
            if (dotProduct(d2,d2) < (double)0.02) {
                vectorSubtract( d, a, d2 );
            }
        }
        crossProduct( d1, d2, plane );
        if ( vectorNormalize( plane, plane ) == 0 ) {
            return false;
        }
        plane[3] = -dotProduct( a, plane );

        return true;
    }

}