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Dr.j
Registered: Feb 2003
Posts: 277 |
help with delay table making tech tech
Hey there again. i want to do a little tech tech effect.
i think i manage Ok with the charsets (took me some time to
arrange right the chars) and i have $d018 and $d016 tables
the main problem is now.. Delay tables . i use this routine
what is the best technique to do "Fine tune" the delays?
i will gladly hear your ideas to do fast delay tables.
i first tried to replace $d016+$d018 with $d021 but it didnt help me much. please don't send me to "missing cycles" article..hehe . btw i don't have any problems to make "rasters" delays but here its different.
ldx #$00
loop:
lda d018tab,x
sta $d018
lda d016,x
sta $d016
ldy delaytab,x
dey
bne *-1
inx
cpx #$2f
bne loop
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algorithm
Registered: May 2002
Posts: 705 |
How are you able to change d018 at any vertical position? You would need to force a badline unless the sinus wave is calculated in a way taking into account when d018 can be switched. |
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tlr
Registered: Sep 2003
Posts: 1790 |
@algorithm: the usual way is to switch the charsets not the screen memory. |
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algorithm
Registered: May 2002
Posts: 705 |
I was thinking of the other method involving screen mem instead of gfx data and adjusting d018 with a long sinus wave. This elimates the issue of using forced badlines |
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chatGPZ
Registered: Dec 2001
Posts: 11386 |
are you sure what tech tech is? how would a specialised sine table help at all? |
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Radiant
Registered: Sep 2004
Posts: 639 |
Groepaz: Well, if you could construct your table so that xscroll would cross character boundraries only on even 8th lines it would work... Never heard of it being used though, and it seems pretty limiting compared to the standard shifted charset method. |
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tlr
Registered: Sep 2003
Posts: 1790 |
If you combine the screen method with the charset method you could do a much wider tech-tech without requiring too many charsets. |
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Conjuror
Registered: Aug 2004
Posts: 168 |
tlr: The consequence of that is the FLI bug as you need to trigger a bad-line to change the charset every line as I did here Better
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Radiant
Registered: Sep 2004
Posts: 639 |
Conjuror: Nah, if your slope isn't too steep you'd only need to update screen RAM location every 8 lines. |
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tlr
Registered: Sep 2003
Posts: 1790 |
Yes, what radiantx said. I'm sure it's been done already. |
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algorithm
Registered: May 2002
Posts: 705 |
I may be wrong but i believe one of the crest demos from maduplec had a part with full 320x200 tech tech utilizing the method of non drastic sine in d016 and changing d018 after 8 raster lines or so allowing the changing of msb nybble (screen ram) which allows more x positions this method
edit: Just seen that part, did not analyse the code, but that demo seems to not use full 320x200 |
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