01.31.05
One Feature Down, Three to Go
I was finally able to debug the full-screen dynamic masking feature of the engine which will allow sprites to be placed behind foreground graphics, which will make for really nice effects. This is also a critical feature in order to bring the engine up to parity with the NES’ priority bit behavior. This feature is used to good effect in SMB3 where Mario could fall “behind” the screen by holding down on the big white blocks.
The next phase of work will focus on cleaning up the modularity of the blitter code. Right now the blitter assumes a rectangular screen and I plan to remove this limitation by making the blitter more table-driven. Also, each line that is drawn by the blitter has several internal bits set which determine what code path to take. This is currently limited to specializing for even/odd aligned blits and spite/non-sprite lines. This mechanism will be generalize and exposed to the engine programmer in order to mix and match different blitter mechanism for a given update. Once these changes are in place, it should be quite simple to create a demo which incorporates a pseudo-three-layer parallax effect.
The final feature to integrate is applying the idea described in a previous post which will provide a full-screen, independent scrolling background. Since this is all blitter related work, this will all be done concurrently.