source/maths/Ease.h

   1 /* Copyright (C) 2012 Wildfire Games.
   2  * This file is part of 0 A.D.
   3  *
   4  * 0 A.D. is free software: you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License as published by
   6  * the Free Software Foundation, either version 2 of the License, or
   7  * (at your option) any later version.
   8  *
   9  * 0 A.D. is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  * GNU General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License
  15  * along with 0 A.D.  If not, see <http://www.gnu.org/licenses/>.
  16  */
  17
  18 #ifndef INCLUDED_EASE
  19 #define INCLUDED_EASE
  20
  21 /*
  22  * Straightforward C++ port of Robert Penner's easing equations
  23  * http://www.robertpenner.com/easing/
  24  *
  25  * Copyright (c) 2001 Robert Penner
  26  * All rights reserved.
  27  *
  28  * Redistribution and use in source and binary forms, with or without modification, are permitted
  29  * provided that the following conditions are met:
  30  *     - Redistributions of source code must retain the above copyright notice, this list of
  31  *       conditions and the following disclaimer.
  32  *     - Redistributions in binary form must reproduce the above copyright notice, this list of
  33  *       conditions and the following disclaimer in the documentation and/or other materials provided
  34  *       with the distribution.
  35  *     - Neither the name of the author nor the names of contributors may be used to endorse or
  36  *       promote products derived from this software without specific prior written permission.
  37  *
  38  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR
  39  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
  40  * FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
  41  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  42  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  43  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER
  44  * IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
  45  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  46  */
  47
  48 #include <math.h>
  49
  50 /**
  51  * Generic easing functions. In each function, the parameters are:
  52  *
  53  * @param t Current time in seconds, as a float between 0 and d (inclusive).
  54  * @param d Total duration of the ease, in seconds. Must be strictly positive.
  55  * @param b Baseline value (at t = 0).
  56  * @param c Delta from baseline value to reach the target value (at t = d). I.e., target = b + c.
  57  *
  58  * Each function outputs the eased value between 'b' and 'b+c' at time 't'.
  59  */
  60 class Ease
  61 {
  62 public:
  63         static float QuadIn(float t, const float b, const float c, const float d)
  64         {
  65                 t /= d;
  66                 return c*t*t + b;
  67         }
  68
  69         static float QuadOut(float t, const float b, const float c, const float d)
  70         {
  71                 t /= d;
  72                 return -c * t*(t-2) + b;
  73         }
  74
  75         static float QuadInOut(float t, const float b, const float c, const float d)
  76         {
  77                 t /= d/2;
  78                 if (t < 1)
  79                         return c/2*t*t + b;
  80                 --t;
  81                 return -c/2 * (t*(t-2) - 1) + b;
  82         }
  83
  84         static float CubicIn(float t, const float b, const float c, const float d)
  85         {
  86                 t /= d;
  87                 return c*t*t*t + b;
  88         }
  89
  90         static float CubicOut(float t, const float b, const float c, const float d)
  91         {
  92                 t = t/d - 1;
  93                 return c*(t*t*t + 1) + b;
  94         }
  95
  96         static float CubicInOut(float t, const float b, const float c, const float d)
  97         {
  98                 t /= d/2;
  99                 if (t < 1)
 100                         return c/2*t*t*t + b;
 101                 t -= 2;
 102                 return c/2*(t*t*t + 2) + b;
 103         }
 104
 105         static float QuartIn(float t, const float b, const float c, const float d)
 106         {
 107                 t /= d;
 108                 return c*t*t*t*t + b;
 109         }
 110
 111         static float QuartOut(float t, const float b, const float c, const float d)
 112         {
 113                 t = t/d - 1;
 114                 return -c*(t*t*t*t - 1) + b;
 115         }
 116
 117         static float QuartInOut(float t, const float b, const float c, const float d)
 118         {
 119                 t /= d/2;
 120                 if (t < 1)
 121                         return c/2*t*t*t*t + b;
 122                 t -= 2;
 123                 return -c/2 * (t*t*t*t - 2) + b;
 124         }
 125
 126         static float QuintIn(float t, const float b, const float c, const float d)
 127         {
 128                 t /= d;
 129                 return c*t*t*t*t*t + b;
 130         }
 131
 132         static float QuintOut(float t, const float b, const float c, const float d)
 133         {
 134                 t = t/d - 1;
 135                 return c*(t*t*t*t*t + 1) + b;
 136         }
 137
 138         static float QuintInOut(float t, const float b, const float c, const float d)
 139         {
 140                 t /= d/2;
 141                 if (t < 1)
 142                         return c/2*t*t*t*t*t + b;
 143                 t -= 2;
 144                 return c/2*(t*t*t*t*t + 2) + b;
 145         }
 146 };
 147
 148 #endif // INCLUDED_EASE