[C#] How to transform world space to local space?

The problem may be that raycasts expect inputs in world space. So shooting a ray based on an object's rotation usually involves changing from local to world. Not world to local. Yes, it is confusing when you think too much about it.

For example, say you have Raycast(transform.right, ...). "right", or (1,0,0), is the direction your local space, which is useless as it is. transform.right converts to the real, world, direction. It's all in one line, so looks semi-magical. But it's just math, then a raycast, like any other function call.