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F18A and XB


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#26 Opry99er OFFLINE  

Opry99er

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Posted Mon Apr 24, 2017 7:41 PM

That's cool... So when BASIC or XB accesses the VDP, it is actually accessing the F18A VDP and unlocking it gives an XB program access to some/all the enhanced features?

Me likey. With some oranges and browns, I might be able to make the Halloween game I have been wanting to write. :)

Somehow, magenta and cyan don't cut the mustard for pumpkins and dead leaves... ;)

#27 PeteE OFFLINE  

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Posted Yesterday, 11:03 AM

In Skyway I have the opposite issue: I'm relying on the 4 sprites per line limitation to mask off sprites when they reach the lower third of the screen. But the jumper setting that most people are using on their F18As means that this trick doesn't work. So I will have to detect the F18A and set up the #sprites-per-line register in order to make my code work as intended, which is a bit annoying (note that I haven't actually done this yet).

If you have a spare sprite pattern or two, I think you could copy the pattern of the sprite that overlaps the bottom of the screen and clear the lines of the sprite pattern that would be over the edge.  That ought to work regardless of the setting of the jumper.



#28 Asmusr OFFLINE  

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Posted Yesterday, 12:23 PM

If you have a spare sprite pattern or two, I think you could copy the pattern of the sprite that overlaps the bottom of the screen and clear the lines of the sprite pattern that would be over the edge.  That ought to work regardless of the setting of the jumper.

 

The sprites are moving down from the top of the screen and need to disappear at line 128 as if this was the bottom of the screen. If I understand your idea correctly you would need up to 15 different versions of a pattern to accomplish what I can do simply by placing 4 high priority sprites at line 128.



#29 PeteE OFFLINE  

PeteE

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Posted Yesterday, 1:03 PM

 

The sprites are moving down from the top of the screen and need to disappear at line 128 as if this was the bottom of the screen. If I understand your idea correctly you would need up to 15 different versions of a pattern to accomplish what I can do simply by placing 4 high priority sprites at line 128.

Well, no -- I was suggesting modifying one pattern on-the-fly as the sprite crosses the line.  Suppose you have a sprite at line 120, so the bottom half of the sprite hangs over the line 128.  Make the bottom half invisible by clearing bytes 08-0F and 18-1F of the sprite pattern.  If the sprite then moves to 124, clear bytes 04-0F and 14-1F of the sprite pattern.  Granted, it's a lot more complicated than just plopping higher priority sprites on line 128.






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