Door opens with the Asset Warp tool

Hello.

Looking for advice on how to use the Asset Warp Tool.

I've placed a bitmap of a door into an HTML5 canvas. I've added a pin to each corner of the door/bitmap, and I want to move the pins furthest away from the hinges diagonally towards the centre, so it looks like the door is opening.

Is there a way to control the pins so the door doesn't become 'liquidy'?

Thanks