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Trash
Registered: Jan 2002
Posts: 122 |
D017 stretch
I have a little while trying out som d017-stretching-code-magic-stuff. It seems impossible to stretch sprite 00 when it is alone a raster row.
Can anyone confirm it is possible or tell med where I am going wrong? I just cant get the timings right and I've tried all combinations (I think?).
I've put 1 -> d017 on all cycles after dec $d016 and then 0 on all cycles after that but for me it seems impossible...
Any help at all would be greatly appriciated!
lda #1
ldy #8
- dec $d016 ; 6 Removes the border
cmp #$c9
sta $d017 ; Has been moved around
cmp #$c9
bit $ea
sty $d017 ; Has been moved around
cmp #$c9
cmp #$c9
cmp #$c9
cmp #$c9
cmp #$c9
cmp #$c9
cmp #$c9
cmp #$c9
cmp #$c9
cmp #$c9
cmp #$c9
cmp #$c9
cmp #$c9
cmp #$c9
sty $d016 ; Makes sure the border is removable
inx
cpx #15
bne -
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chatGPZ
Registered: Dec 2001
Posts: 11090 |
never put your thumb into the sideborder, girlfriend said |
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Smasher
Registered: Feb 2003
Posts: 511 |
let's make a demo about it. |
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Trash
Registered: Jan 2002
Posts: 122 |
Sorry for my stupid question, of course it works to stretch a single sprite with d017 while removing the border (even S#00). You just have to stop being stupid and do it the right way :-( |
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The Phantom
Registered: Jan 2004
Posts: 360 |
Meh. Whatever.
Good luck. |
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Oswald
Registered: Apr 2002
Posts: 5017 |
NOS intro at DOTC 1 sided is having sideborder off + 8 sprites stretched differently ?
Defender of the Crown +9D |
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HCL
Registered: Feb 2003
Posts: 716 |
..isn't that what i told you from the beginning Trash? Just do it the right way! :) |
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Trash
Registered: Jan 2002
Posts: 122 |
Quote: ..isn't that what i told you from the beginning Trash? Just do it the right way! :)
According to you everything is easy, just some lda and sta's in the right place and the sky is the limit... |
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Compyx
Registered: Jan 2005
Posts: 631 |
For some reason when doing an 8-sprite open border routine you have to use DEC $d016 + INC $d016.
This has something to do with sprite 0 DMA eating too many cycles from the CPU, so the $d016 writes don't happen at the right time, occupying the CPU with DEC/INC solves that.
I found this out the hard way, back when I still actively coded demos. The explanation might be a bit off, but I'm sure there's VIC-II guru's out here who can do a better job than I do.
But like others have mentioned, when you don't need all 8 sprites, avoid sprite 0. |
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Graham
Account closed
Registered: Dec 2002
Posts: 990 |
Explanation is easy: DEC $D016 has 2 write cycles at the end of it's execution, while STA $D016 has only one. The 6510 cannot be stopped on write cycles, so with the right timing you can skip 2 of the 3 bus allocate cycles of the sprite #0 DMA which gets you right to the exact cycle where $D016 has to be changed to open the side border. |
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Compyx
Registered: Jan 2005
Posts: 631 |
Thanks Graham,
That explains the sprite 0 nastiness a lot better than I did :) |
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