iTweenで使えるEaseTypeはRobert Penner’s open source easing equationsを元にしているそうです。
使えるTypeの一覧
| easeInQuad | easeOutQuad | easeInOutQuad |
| easeInCubic | easeOutCubic | easeInOutCubic |
| easeInQuart | easeOutQuart | easeInOutQuart |
| easeInQuint | easeOutQuint | easeInOutQuint |
| easeInSine | easeOutSine | easeInOutSine |
| easeInExpo | easeOutExpo | easeInOutExpo |
| easeInCirc | easeOutCirc | easeInOutCirc |
| easeInBounce | easeOutBounce | easeInOutBounce |
| easeInBack | easeOutBack | easeInOutBack |
| easeInElastic | easeOutElastic | easeInOutElastic |
| linear | spring |
どんな感じかグラフで見たい場合は次のリンクが参考になるかなと思います。
Easing Functions Cheat Sheet
https://easings.net/
リンク
iTween for Unity by Bob Berkebile (pixelplacement)
http://www.pixelplacement.com/itween/documentation.php
Robert Penner’s Easing Functions
http://robertpenner.com/easing/