Originally Posted by trydowave
When I see games like Lionheart running on a stock A500 I know that the Amiga could handle Parallax on a game like BC kid. As for SF2. In the right hands I bet we could of had a pretty decent conversion.
The type of parallax effect used in BCKid PC engine is indeed easy to replicate on the Amiga but it is very important to realize that not all parallax scrollings are created equal.
It is easy both on the PC Engine and one the Amiga to create a parallax effect composed of non-overlapping
(that is the key word) horizontal slices covering the entire screen width and scrolling at different speeds.
=> Just modify the scroll registers for each section. For both platforms.
That's the one used in BCKid.
However, some forms of parallax scrolling will always be out of reach of the Amiga: tile based parallax effects where the tiles composing the background part of the scenery are animated so as to simulate that they are scrolling when the rest of the screen is not.
This effects is extensively used on the C64 (Manfred Trenz made great use of it) and on consoles and is a very low-cost way to simulate a parallax layer on hardware which does not technically have multiple layers. (The NEC PC Engine has only one tile layer.)
The Amiga cannot use it because it has bitmap based graphics and scrolling two overlapping parts of the screen at different speeds requires modifying the whole surface of the bitmap which is scrolling and (usually) costs way too much either in CPU or blitter.
This said I think I have found a way to create vertical two layers parallax effect on any bit plane depth at a very reasonable cost but I need to validate the technique before I make a fool of myself officially.