Re: What doesn't work: greyscale in software :-)

Ha, I knew I didn't try hard enough!

I'll wait for another lazy Sunday afternoon to come around to try again... unless someone else wants to give it a shot!

I can envision using James's suggestion in particular as a way to do some iteration-based shading in the bare-metal version of LisaMandelbrot.

If anyone else would like to help resurrect the Lisa demoscene, I bet the parallel port could drive a suitably-wired Covox Speech Thing as well. If you have a parallel port card, you could do stereo :-D

--Tom

On Sunday, March 11, 2018 at 7:53:32 PM UTC, James MacPhail wrote:
>
>
> If black/grey/white is sufficient, you could use two or three screen
> buffers and switch between them on alternate scans by changing the
> video page latch.
>
> >Try tying it to the STATREG register to get the vertical refresh irq
> >edge transition and then use exactly coded opcodes to bit bang the
> >contrast output.
> >
> >Look at the serial number decode in the room source.
> >
> >>-------- Original message --------
> >>From: Tom Stepleton <step..._at_email.domain.hidden <javascript:>>
> >>I was not able achieve a useful greyscale effect on the
> >>Lisa's display by changing the values in the video contrast register
> >>as fast as I could.
> >>
> >>It would be interesting to hear from knowledgeable folks if they
> >>think I'm wrong in concluding that changing the beam intensity
> >>"mid-flight" is not really possible.
>

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