Switching Copperlists

[DanielAllsopp]

Hey all!

During specific positions in my game I am switching between two copper lists, which is working to a degree; the problem is I get a nasty flicker when the switch occurs.

I set the initial list using

move.l #PrimaryCopper,COP1LCH(a6)

but then switch to the second list with a subsequent

move.l #SecondaryCopper,COP1LCH(a6)

.

Something doesn't quite seem right though, so is this a valid way to switch between two copper lists using the CPU?

Cheers

[paraj]

How and when are you switching? The new copperlist won't be active until the next vblank (unless you explicitly jump to it by strobing COPJMP1). If you're doing this in the visible area and immediate start updating PrimaryCopper or if SecondaryCopper isn't ready for the next frame you'll get interesting results.

Make sure SecondaryCopper is fully initialized and switch after PrimaryCopper has finished (but before line 0) and you should be good.

[DanielAllsopp]

Originally Posted by paraj

How and when are you switching? The new copperlist won't be active until the next vblank (unless you explicitly jump to it by strobing COPJMP1). If you're doing this in the visible area and immediate start updating PrimaryCopper or if SecondaryCopper isn't ready for the next frame you'll get interesting results.

Make sure SecondaryCopper is fully initialized and switch after PrimaryCopper has finished (but before line 0) and you should be good.

Cool, makes sense but how does one know when a copper list is actually finished?

Would I wait until the end of a frame?

[paraj]

Originally Posted by DanielAllsopp

Cool, makes sense but how does one know when a copper list is actually finished?

Would I wait until the end of a frame?

The easy answer is: wait for an Y position that's later than the last line you care about. I.e. just beyond the end of the visible frame. You wrote PrimaryCopper so you know when it's done. Find the last WAIT in it and wait for a line just below that (unless you're doing really complicated stuff).


I.e. if you're changing the background color on line 301 just after your playfield has finished displaying, wait for line 302.


If in doubt, post your copper list (starting from at least the last WAIT).

[DanielAllsopp]

Fixed The bitplane pointers in the second copperlist were uninitialised and obviously containing garbage, so that's what was initially showing when I switched it over.

Thanks for the pointers, it all helped!