I thought the visual effect using a projection on plexiglass at a 45* angle was the pepper's ghost effect and musion was a projection on a black "net" screen
I hope that kitty moves to a portrait and finds a friend to hang out with
here is the decription from the site.
It is not a black screen because logically light do not reflect in black.
here is the quote.
"In particular, the invention relates to the use of a transparent foil stretched across the path of the projector as a screen, the foil having similar reflective properties to semi-mirrored glass.."
like a semi-mirror foil, best example is the silver screen of fake IMAX (of course musion is much more thin) with so many holes that backlight can be seem therefore
making it transparent but at the same time, stops the projector lights complete for the holographic image to hold.
--- Update ---
about the pepper ghost thing
eventho musion is not pepper ghost (becasue it makes pepper ghost makes the reflect image transparent)
the kept the 45 degree angle on the screen because they can not shoot out the projector straight up from the back
because you would have see the projector light hitting your face.
so like the old days, the projector has to be set at a angle that the projected light will never hit anyone and be seen
Tower of Terror and other disney attraction either set the projector on the top shooting downward, therefore the light is towards the ground,
so you wont see it. or from the side, where the light will shoot towards another part of the set that is blocked from the sight of the guests.
I have no idea where they would set up the projector for the dumbledore effect.
I would belive is probably behind and under the near the ground shooting upwards from that balcony that he is standing behind of.