tests/java_api/VrDemo/src/com/example/android/rs/vr/engine/VectorUtil.java

/*
 * Copyright (C) 2015 The Android Open Source Project
 *
 * 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 com.example.android.rs.vr.engine;

/**
 * Some minimal utilities for Vector math
 */
public class VectorUtil {
    public static void sub(double[] a, double[] b, double[] out) {
        out[0] = a[0] - b[0];
        out[1] = a[1] - b[1];
        out[2] = a[2] - b[2];
    }

    public static void mult(double[] a, double b, double[] out) {
        out[0] = a[0] * b;
        out[1] = a[1] * b;
        out[2] = a[2] * b;
    }

    public static double dot(double[] a, double[] b) {
        return a[0] * b[0] + a[1] * b[1] + a[2] * b[2];
    }

    public static double norm(double[] a) {
        return Math.sqrt(a[0] * a[0] + a[1] * a[1] + a[2] * a[2]);
    }

    public static void cross(double[] a, double[] b, double[] out) {
        double out0 = a[1] * b[2] - b[1] * a[2];
        double out1 = a[2] * b[0] - b[2] * a[0];
        double out2 = a[0] * b[1] - b[0] * a[1];
        out[0] = out0;
        out[1] = out1;
        out[2] = out2;
    }

    public static void normalize(double[] a) {
        double norm = norm(a);
        a[0] /= norm;
        a[1] /= norm;
        a[2] /= norm;
    }

    public static void add(double[] a, double[] b,
                           double[] out) {
        out[0] = a[0] + b[0];
        out[1] = a[1] + b[1];
        out[2] = a[2] + b[2];
    }

}