src/com/replica/replicaisland/Lerp.java

/*
 * Copyright (C) 2010 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.replica.replicaisland;

public final class Lerp {
    
    public static float lerp(float start, float target, float duration, float timeSinceStart)
    {
        float value = start;
        if (timeSinceStart > 0.0f && timeSinceStart < duration)
        {
            final float range = target - start;
            final float percent = timeSinceStart / duration;
            value = start + (range * percent);
        }
        else if (timeSinceStart >= duration)
        {
            value = target;
        }
        return value;
    }

    public static float ease(float start, float target, float duration, float timeSinceStart)
    {
        float value = start;
        if (timeSinceStart > 0.0f && timeSinceStart < duration)
        {
            final float range = target - start;
            final float percent = timeSinceStart / (duration / 2.0f);
            if (percent < 1.0f)
            {
                value = start + ((range / 2.0f) * percent * percent * percent);
            }
            else
            {
                final float shiftedPercent = percent - 2.0f;
                value = start + ((range / 2.0f) * 
                        ((shiftedPercent * shiftedPercent * shiftedPercent) + 2.0f));
            }
        }
        else if (timeSinceStart >= duration)
        {
            value = target;
        }
        return value;
    }
}