Interlace modes, V/H scrolling, Sonic 2 multiplayer queries

[BigEvilCorporation]

Hi!

I'm trying to determine how Sonic 2's multiplayer allows for the top half of the screen to vertically scroll independently from the lower half.

In my game I'd like a portion of plane B to remain static whilst the rest scrolls. In my head this could be achieved by setting the scroll size 64 cells high and only utilising the upper 32 for the usual scrolling background, then dropping the V scroll for the static section down to the lower 32. In practice this doesn't work because the H scrolling affects the source line and not the currently rastered line.

But, Sonic 2 looks like it's achieving this. Is this a bonus of interlace mode?

Cheers

[Sik]

It's changing the scroll values during the split part, not just loading a new sprite table. (and you can specify the horizontal scroll for every line too without even raster effects, that's the whole point of the table)

What are you trying to do though? Because if it's something like the HUD in Toki you may just use the window plane instead =P

[BigEvilCorporation]

It's changing the scroll values during the split part

That simple eh? I'll give that a try!

What are you trying to do though? Because if it's something like the HUD in Toki you may just use the window plane instead =P

Most of the level is outdoors, with a scrolling left-to-right landscape in the background. One part of the level heads indoors, and I would like a separate, but static background (the foreground plane needs to remain in front of the spites, though).

I can't spare any VRAM for the Window plane, but I'll definitely take a look at Toki (especially since that's the name of my bearded dragon!).