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Forums > C64 Coding > Weird graphics glitches with a SCPU program
2016-10-27 15:14
Majikeyric

Registered: Sep 2002
Posts: 72
Weird graphics glitches with a SCPU program

Hi coders,

I'm actually working on a game engine for SCPU (yes there are crazy people ;)
the following video shows a bitmap scrolling with the Aladdin character made of sprites, I can't understand why there are those glitches in the bitmap (when there are no sprites on screen, there are no more glitches..).

https://www.youtube.com/watch?v=dAgFAMAYiyA

Did some of you already experience that problem ???
Is it VIC-II or SCPU related ???
2016-10-27 15:35
Oswald

Registered: Apr 2002
Posts: 4090
looks like a timing problem in your code, exactly when middle gray raster line on border shows up the glitch occurs. maybe you copy new data into bitmap while its being shown ?
2016-10-27 15:38
AmiDog

Registered: Mar 2003
Posts: 92
The usual suspect when I have weird issues when doing SCPU coding, is that I've forgotten to switch the CPU to 8bit accumulator when accessing the IO area and thus end up overwriting a register I wasn't supposed to be touching :-)
2016-10-28 19:02
Thunder.Bird

Registered: Nov 2003
Posts: 61
Maybe it has something to do with your previous SCPU Problem?
https://www.youtube.com/watch?v=Qqs_XYEsbvY
Also check PSU and PLA
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