Friday, May 23, 2008

XeO3: C64 stars!

I've just spent an hour playing with the C64's starfield. I've never been terribly happy with it as it shimered a lot due to the 1 pixel smooth scroll. So I've finally gotten round to making them HIRES rather than MCM stars. This involves doing the stars in the VBlank and setting/clearing the colour depending on whats already in that location.

It also takes a good few scanlines to run, but I can't see anyway of making it faster! It simply has lots to do so I'm probably stuck with it! I'll have to be careful though, because if the multiplexor gets busy then it's probably going to need the time the stars are eating up. Theres probably a couple of places I can stick the stars routine, but due to the colour writes it has to be in the FLIP vblank!

Oh well, its okay just now as the multiplexor isn't getting taxed very much - in fact it hardly every gets used! This is because the Plus/4 version keeps sprites free so that if coins are falling, I can still bring on new baddies without having to worry about the coins eating up slots. Still, it looks reasonably busy and I can always add more I guess.

I'm wondering if I should upload a video of the C64 version playing... but I dont really want to spoil the demo by letting people see it play through. So I'll probably wait until the Plus4 version is out for a little, then release a video afterwards.....

So stars done.... Panel next!


TNT said...

Hi Mike, good to see you back! I only noticed it today.

I did split PR background star (visible after you finish deck) redraw into two parts, that way it doesn't flicker on NTSC. Upper part of screen is updated right after display beam has done drawing it, lower part is drawn while raster is already drawing the upper part next time. PAL C64 manages to do all the drawing before display starts again.

I don't know if you can split star update into two halves, but it might be worth a try.

Mike said...

Yeah might be worth a shot, although I'll wait until I really need to do it!