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By dvik

Prophet (2199)

dvik's picture

19-01-2019, 23:33

Hi,

While working on the V9958 emulation I ended up a bit confused about how horizontal scroll works (in particular the lower 3 bits and edge masks). If someone could help me understand I'd be very thankful.

What I'm trying to fully understand is how the first 24 pixels of a scan line (including border) is rendered given the horizontal scroll register. Assume with hscroll = 0, the following pixels are rendered (I assume):

b b b b b b b b 0 1 2 3 4 5 6 7 x x x x x x x

where b is 8 left border pixels and x'es are the next 8 pixels on the scan line.

so first question: With hscroll = 1 how are the pixels 0-7 mapped (e.g.):
b b b b b b b 0 1 2 3 4 5 6 7 x x x x x x x x

second question assume border masking is set, which pixels are masked (both in the hscroll = 0 case and when hscroll = 1)

third question, how is border masking looking at the right border?

Any thoughts that can help me fully understand this is appreciated.

By dvik

Prophet (2199)

dvik's picture

22-01-2019, 08:14

Thanks for feedback and help.

@NYYRIKKI: I fixed several bugs in the command engine and the renderers so the Alt demo runs (almost) correct now. Still puzzled about the blink color issue.

I Also fixed some minor MoonSound issues, and I added a special rom insert menu to add MSX Audio and Moonsound easily.

The command engine fixes I'd like to port back to mother blue as the web version now has (apart from new unknown bugs possibly introduced) better emulation.

Check it out and lmk what you think.

By Parn

Champion (349)

Parn's picture

23-01-2019, 19:22

@dvik, has anyone answered your question about the V9958 horizontal scroll registers? I don't see any messages between your last one and your previous one. I think I can help if it's still needed, but I wouldn't want to waste forum space if it isn't.

By mars2000you

Enlighted (5454)

mars2000you's picture

23-01-2019, 19:32

The answers have been given in this specific thread: https://www.msx.org/forum/msx-talk/emulation/help-understand...

By dvik

Prophet (2199)

dvik's picture

23-01-2019, 22:04

Thanks, Yes it was answered and I implemented the change, however I don't mind hearing your explanation as well because I'm still not 100% confident I got it right. wouter_@ gave me good insight and the latest version is a quite big improvement and I also did some smaller but quite impactful fixes in the command engine. So now beppin and the alt demo works almost 100%. One small potential issue is in the last scroller in the alt demo where I would expect masking to look different. So happy to hear your explanation of the hscroll.

By Parn

Champion (349)

Parn's picture

24-01-2019, 23:46

Ok, I'll post my observations on that thread as well. Smile

By ren

Paragon (1194)

ren's picture

17-04-2019, 16:01

Cool to see some development again here.

I concur with what Garudian said earlier (page 3): having these changes find their way to the Libretro core would be pretty awesome.

I don't care much for the web version myself (ATM): it lacks features and seems slow. (Though the latter may also have to do with my browser config/settings.)

Since there's WebMSX, which seems to do a pretty good & cool job already, my vote would go to the invest into the Libretro core option as well here Smile

Cheers!

ps: I'll test some stuff in the latest version when I have some time.

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