Tweening

Tweening is a technique to improve animations in RuneScape. Released in in July 2009, it creates a smoother and better-to-look-at animation than before. Originally animations have 25 frames per second however with tweening two frames of animation are interpolated (blended together) to create a third frame in between them. This makes the animation appear smoother to the eye as it effectively doubles the frames of the animation putting them at the game's limitation of 50 frames per second.

Here is a comparison of without and with tweening, respectively: