Here you can find the source of interpolate(double fromAngle, double toAngle, double ratio)
private static double interpolate(double fromAngle, double toAngle, double ratio)
//package com.java2s; /* /* w w w . j a va 2 s.co m*/ * The MIT License * * Copyright 2016 Benny Lutati. * * Permission is hereby granted, free of charge, to any person obtaining a copy * of this software and associated documentation files (the "Software"), to deal * in the Software without restriction, including without limitation the rights * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell * copies of the Software, and to permit persons to whom the Software is * furnished to do so, subject to the following conditions: * * The above copyright notice and this permission notice shall be included in * all copies or substantial portions of the Software. * * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN * THE SOFTWARE. */ public class Main { /** Interpolates angle according to rate, * with correct 0->360 and 360->0 transitions */ private static double interpolate(double fromAngle, double toAngle, double ratio) { double delta = toAngle - fromAngle; if (Math.abs(delta) > 180) { toAngle += delta > 0 ? -360 : 360; } return normalize(fromAngle + ratio * (toAngle - fromAngle)); } /** Converts angle to range 0-360 */ private static double normalize(double angle) { while (angle > 360) { angle -= 360; } while (angle < 0) { angle += 360; } return angle; } }