Building Layouts - Unity 3D UI Essentials - page 49

The Rect Transform component is included with all Unity UI objects added to the
scene instead of the regular Transform component and forms a core part in the
layout of all Unity UI controls.
If you add a Rect Transform component to any GameObject,
it will automatically replace the Transform component. If you
remove the Rect Transform component it will revert back to the
standard Transform component.
With UI components, the Rect Tool also reacts to the control modifiers in the
toolbar, depending on what they are currently set to, as you can see in the following
screenshot there are two modifier buttons, each with two settings:
When you have the Rect Tool selected, these toggles behave as follows for a
UI component:
• Center : The central pivot point of the Rect selection area acts as an anchor;
holding the mouse down on it moves the Rect around the screen.
• Pivot : With this option active, holding the mouse down on the pivot
point of the selection Rect moves the pivot point around the object, thus
altering the pivot point for the object (the point at which the object is
rotated/scaled around).
• Global : When in global mode, the selection area for a Rect Transform
surrounds the entire object including any rotated space. If the Rect is rotated,
the selection area stays un-rotated and sizes up to encompass all the used
space by the Rect.
• Local : When in local mode, the selection area is tight to the Rect Transform
area with rotation; if rotated, the selection area is also rotated.
Remember, the Pivot point of a source image and the Pivot point
of the Rect Transform are two separate things; altering the Pivot
point of the Rect Transform does not alter the Pivot point of the
source sprite/image.