Exactly how it works is beyond my understanding, and an embedded alpha channel certainly makes sense.  Also the default-to-white explains some ground textures which turn silver if the light is low and the camera angle wrong.
In my post though I was simply musing aloud while addressing BuilderBob's statement that alpha channels were purplish if viewed in a graphics program. If so viewed Alpha channels are greyscale but Normals have a purplish look...
Andy
				
			In my post though I was simply musing aloud while addressing BuilderBob's statement that alpha channels were purplish if viewed in a graphics program. If so viewed Alpha channels are greyscale but Normals have a purplish look...
Andy