Expanding size of a primitive in a single direction?

Is there a way to modify the size of a primitive from a single side of that primitive? for example if i have a square sitting on a quad and want to increase its height in the y direction but only in the positive direction, how do you do that instead of it expanding itself in both directions?

 

Generally speaking, you don't. Unity's primitives aren't intended as a modelling solution. If you need more than basic shapes you'll generally want to get some modelling software to make them with.

There are ways you can get some variation in the shape, though. If you give your shape a parent GameObject and offset the shape within the parent, then you can scale it out from the parent's position instead of from the mesh's pivot. This gets complicated and messy quickly, so I wouldn't recommend doing anything non-trivial with it.

 

You can set the pivot to the opposite end of the side you want to scale and then scale the object.

 

Make runtime calculation with scale + position ration.

So say I scale my object's width by 1 unit from left to right. So move that object by 1 unit to the right to offset it's scale.