vsprites & interlace
2 messages in this thread
Is there something special you have to do to get vsprites to work with
interlace mode? Everything works fine in non-interlace, but strange things
start happening when I switch modes. The sprites start disappearing and
reappearing as they move around the screen. Anyone have an idea?
Rick:
When you say you are going "to interlace", do you mean you simply flip the
display into interlace, or are you doubling the screen height (from, say,
200 to 400 lines)? If you are running 4 bitplane graphics (16 color), and
you change from a 640 x 200 to a 640 x 400 screen, most of the CHIP DMA
will be used to move the screenbits out to video. In this environment,
very, very few of the real sprites will be available for use by the vsprite
software. The visual effect you are witnessing is the vsprite software
running out of real sprites. I believe that it is unable to reuse a sprite
until a scan line or two underneath its bottom raster line. Thus, if more
than 2 or 3 appear together horizontally, some will simply not be there. As
the sprites move vertically away from each other, they will flicker on.
If this is indeed the problem you are seeing, I think you'll have to live
with it. Of course, you COULD use BOBS instead.
Ariel