In Unity you have to consider UI elements with CanvasRenderers that need to be children of a canvas as separate from 'normal' elements with normal Renderer components.
UI Masks like the RectMask2D
and the Mask
component affect UI Images, not Unity's Sprites.
Normal element's mask such as the SpriteMask
component affects Unity's Sprites, but not UI Images.
Same applies when using Spine elements:
UI mask and RectMask2D are affecting SkeletonGraphic only, since it's Spine's UI element.
SpriteMask is affecting SkeletonGraphic and SkeletonMecanim.