Re: [stella] Gunfight 2600: The final Kernel Part 3

Subject: Re: [stella] Gunfight 2600: The final Kernel Part 3
From: Manuel Polik <cybergoth@xxxxxxxx>
Date: Thu, 09 Aug 2001 08:48:25 +0200
Glenn Saunders schrieb:
> >>
> Removed the disturbing black HMOV line.
> <<
> Am I reading this correctly: does this mean that it's possible to have a
> positioning routine that doesn't create an HMOV line, without masking it
> with another sprite?

With 'masking it with another sprite' you possibly mean 'blacking' the
entire 'dirty' area on the left side completely?

Then the answer is: Yes, you can avoid the black lines without any loss
in screen resolution. That's just what I did.
The trick as such is simple, but it's not that easy to actually do it.

'Things that do bad things to HMOVE' or so is the Thread in the archive,
where one of the emulator coders discovered it.

He discovered that *unusual* HMOVEs can have various strange effects,
one of them is _no_ black line, when executed on cycle 74.
That's just what I'm doing now. Apart from timing this, there's another
issue to cope with:

The range of the HMXX values differs, it's shifted like this:

-8  -9 -10 -11 -12 -13 -14 -15   0  -1  -2  -3  -4  -5  -6  -7

In practice it turns out that you've to add 8 pixels to your horizontal
coordinate to position to the correct desired value.

I overlooked the original list article on first sight too, but Thomas
didn't and he thankfully pointed it out to me again.


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