Re: Drawing in overlay planes

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Morten Eriksen (mortene++at++pvv.unit.no)
Fri, 12 Apr 1996 18:55:44 +0200 (MET DST)


On Fri, 12 Apr 1996, Angus Dorbie wrote:

> The problem is that you are not double buffering the overlay planes. Perhaps
> doing this immediately after you swapbuffers() & a finnish() will help, it'll
> be nearer the vertical retrace.

There wouldn't happen to be a routine somewhere that makes it possible
to read the current rasterline-position of the videobeam..? No?
Thought not. :)

> Do you have any other information in the overlay which you want to keep?

Yep. See below.

> Perhaps you don't need the first rectwrite & rectread.
>
> Do you have to do this in the overlay? If your drawing this as a draw callback
> you'd be much better using rgb information and drawing to the framebuffer.
> It'll be double buffered & you won't need to restore the old information.

I'm using the overlay planes during replay to show the trace of how
the user pointed a gun towards the screen during simulation. The
problem is of course that there's no limit (well, that's not entirely
true, there can't be more than width*height unique positions) to how
many pixel positions I have to remember (in either a list or a
storebuffer) and redraw each frame if I decide to use the regular
bitplanes.

Anyone out there who have wrestled with such a problem already?

Anyway, the flickering cursor is just a minor problem - it isn't _too_
ugly to look at, so I guess I'll just leave it at that. Thanks for the
help.

Regards,
Morten


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