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Partz
Account closed
Registered: Jun 2008
Posts: 17 |
Masking char row for vertical scroll
Assuming I want to smooth scroll only part of the screen vertically in an updward direction (say the first 10 char rows) and keep the rest constant, what techniques are available to mask the new characters which need to appear at row 10?. I know that its possible to set an invalid graphics mode which will prevent the characters from being 'seen' as they are plotted but when i've attempted to use this the mask area always appears in black - i've seen some very old games smooth scroll in this direction without having a black mask area so how was this achieved? |
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TNT
Account closed
Registered: Oct 2004
Posts: 189 |
Blank font + $d018 change. |
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T.M.R
Account closed
Registered: Dec 2001
Posts: 749 |
Switch on bitmap mode to a blank area? |
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Graham
Account closed
Registered: Dec 2002
Posts: 990 |
Sprites. |
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Mace
Registered: May 2002
Posts: 1799 |
Either what TNT said, or Graham's method.
Another trick is to slowly fade in the last line by changing the colours.
This doesn't result in the effect you describe, but it DOES solve the problem of suddenly appearing chars :) |
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Cruzer
Registered: Dec 2001
Posts: 1048 |
lda #$7b
sta $d011 |
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Graham
Account closed
Registered: Dec 2002
Posts: 990 |
@Cruzer:
"i've seen some very old games smooth scroll in this direction WITHOUT having a black mask area so how was this achieved?" |
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Partz
Account closed
Registered: Jun 2008
Posts: 17 |
Thanks for all the replies guys. I did think of sprites but didn't know if that was too clumsy - The blank font seems like a nice solution. I guess there are a number of ways of doing this - I just didnt want to go down the path of implementing something when there might have been a well known tried and tested way that everyone else did it. |
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TNT
Account closed
Registered: Oct 2004
Posts: 189 |
$d018 can clip your sprites too if needed - swap screen as well as font and point sprites to blank ones :) |
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Cruzer
Registered: Dec 2001
Posts: 1048 |
@Graham: Oh.. Another proof that I'm a total ignorant. :)
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