Add Interpolation method

src/main/java/org/cora/maths/utils/Interpolation.java

+package org.cora.maths.utils;
+
+/**
+ * Created by ronan-j on 06/06/16.
+ */
+public class Interpolation
+{
+    /**
+     * Compute linear interpolation value
+     * @param start start value
+     * @param end end value
+     * @param duration full animation duration
+     * @param time current time
+     * @return computed value
+     */
+    public static float linearInterpolation(float start, float end, float duration, float time)
+    {
+        // y = ax + b
+
+        float b = start;
+        float a = (end - start) / duration;
+        return a * time + b;
+    }
+
+    /**
+     * Compute exponentiel interpolation value
+     * @param start start value
+     * @param end end value
+     * @param duration full animation duration
+     * @param time current time
+     * @param k base of exp
+     * @return computed value
+     */
+    public static float expInterpolation(float start, float end, float duration, float time, float k)
+    {
+        // y = a * exp(bkx)
+
+        float a = start;
+        float b = (float) (Math.log(end/a) / (k * duration));
+
+        return (float) (a * Math.exp(b * k * time));
+    }
+
+    /**
+     * Compute logarithmic interpolation value
+     * @param start start value
+     * @param end end value
+     * @param duration full animation duration
+     * @param time current time
+     * @param k base of log
+     * @return computed value
+     */
+    public static float logInterpolation(float start, float end, float duration, float time, float k)
+    {
+        // y = a + b * log(kx)
+
+        float r = 1/k;
+        start += r;
+        duration += r;
+        time += r;
+
+        float a = start;
+        float b = (float) ((end - a) / Math.log(k * duration + 1));
+
+        return (float) ( a + b * Math.log(k * time));
+    }
+
+    /**
+     * Compute exponentiel interpolation value
+     * @param start start value
+     * @param end end value
+     * @param duration full animation duration
+     * @param time current time
+     * @param x x pow value
+     * @param k base of pow
+     * @return computed value
+     */
+    public static float powInterpolation(float start, float end, float duration, float time, float x, float k)
+    {
+        // y = a * x^(bkx)
+
+        float a = start;
+        float b = (float) (Math.log(end/a) / (k * duration * Math.log(x)));
+
+        return (float) (a * Math.pow(x, b * k * time));
+    }
+}