VectorUtil.java

// Copyright 2008 Google Inc.
//
// 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.google.android.stardroid.util;

import com.google.android.stardroid.units.Vector3;


public class VectorUtil {
  public static Vector3 zero() {
    return new Vector3(0, 0, 0);
  }
  
  public static float dotProduct(Vector3 p1, Vector3 p2) {
    return p1.x * p2.x + p1.y * p2.y + p1.z * p2.z;
  }
  
  public static Vector3 crossProduct(Vector3 p1, Vector3 p2) {
    return new Vector3(p1.y * p2.z - p1.z * p2.y,
                      -p1.x * p2.z + p1.z * p2.x,
                       p1.x * p2.y - p1.y * p2.x);
  }
  
  public static float angleBetween(Vector3 p1, Vector3 p2) {
    return MathUtil.acos(dotProduct(p1, p2) / (length(p1) * length(p2))); 
  }
  
  public static float length(Vector3 v) {
    return MathUtil.sqrt(lengthSqr(v));
  }
  
  public static float lengthSqr(Vector3 v) {
    return dotProduct(v, v);
  }
  
  public static Vector3 normalized(Vector3 v) {
    float len = length(v);
    if (len < 0.000001f) {
      return zero();
    }
    return scale(v, 1.0f / len);
  }
  
  public static Vector3 project(Vector3 v, Vector3 onto) {
    return scale(dotProduct(v, onto) / length(onto), onto); 
  }
  
  public static Vector3 projectOntoUnit(Vector3 v, Vector3 onto) {
    return scale(dotProduct(v, onto), onto); 
  }
  
  public static Vector3 projectOntoPlane(Vector3 v, Vector3 unitNormal) {
    return difference(v, projectOntoUnit(v, unitNormal)); 
  }
  
  public static Vector3 negate(Vector3 v) {
    return new Vector3(-v.x, -v.y, -v.z);
  }
  
  public static Vector3 sum(Vector3 v1, Vector3 v2) {
    return new Vector3(v1.x + v2.x, v1.y + v2.y, v1.z + v2.z);
  }
  
  public static Vector3 difference(Vector3 v1, Vector3 v2) {
    return sum(v1, negate(v2));
  }
  
  public static Vector3 scale(float factor, Vector3 v) {
    return new Vector3(v.x * factor, v.y * factor, v.z * factor);
  }
  
  public static Vector3 scale(Vector3 v, float factor) {
    return scale(factor, v);
  }  
}