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2015-07-10 10:51

goerp

Registered: Feb 2006
Posts: 21

Half pixel high graphical corruption

I'm working on a drawing program for making SuperHires Pics on the PC. The C64 viewer I made multiplexes 8 sprites, but is badly made so there's some graphical corruption (I guess I need a stable raster, working on that).
On the emulator I get some flickering lines in the sprites, but on a real C64 I get lines that are about HALF a pixel high!
They are stable on the top or bottom of a pixel for a while, then flicker a bit and then flip to the other vertical half.

I read somewhere that PAL has 625 lines that are interlaced, maybe the pixels are showing only in one part of the interlace? Is it something related to the monitor type (I use a simple LG LCD TV).

Is it usable for effects (I would think not because it's so unstable).

The program can be found at: http://www.goerp.nl/C64/c64programs/sh%20viewer.prg
(and yes: there's all kinds of things wrong with it, but I'll get it better).
A screenshot from my TV: http://www.goerp.nl/C64/c64programs/halfpixel.png

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2015-07-11 08:21

goerp

Registered: Feb 2006
Posts: 21

I think it's a hard effect to code for, at least for me. I think I'm not ready for such ambitious endeavours :)

I'll keep it in the back of my mind, but I'm not sure if I would post it here if I ever do something with it. It would be an exploit of my monitor's shortcomings not of my trusty C64.(more likely the monitor will die before I finish something like that).

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