Terrarum/src/net/torvald/terrarum/ui/Movement.kt

package net.torvald.terrarum.ui

import com.jme3.math.FastMath
import net.torvald.terrarum.sqr

/**
 * Created by minjaesong on 2016-03-22.
 */
object Movement{
    /**
     * Fast at the beginning, getting slow over time.
     */
    fun fastPullOut(scale: Float, start: Float = 0f, end: Float = 1f): Float =
            if (scale < 0f) start
            else if (scale > 1f) end
            else (start - end) * FastMath.sqr(scale - 1) + end

    /**
     * Slow at the beginning, getting fast over time.
     */
    fun dropDown(scale: Float, start: Float = 0f, end: Float = 1f): Float =
            if (scale < 0f) start
            else if (scale > 1f) end
            else (end - start) * FastMath.sqr(scale) + start

    fun sinusoid(scale: Float, start: Float = 0f, end: Float = 1f): Float =
            if (scale < 0f) start
            else if (scale > 1f) end
            else (start - end) * FastMath.cos2(0.5f * FastMath.PI * scale) + end
    fun moveQuick(start: Float, end: Float, timer: Float, duration: Float) =
            (start - end) * ((timer / duration) - 1).sqr() + end
    fun moveLinear(start: Float, end: Float, timer: Float, duration: Float): Float {
        val scale = timer / duration
        if (start == end) {
            return start
        }
        if (scale <= 0f) {
            return start
        }
        if (scale >= 1f) {
            return end
        }
        return ((1f - scale) * start) + (scale * end)
    }
}