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Forums > C64 Coding > How are some effects done?
2006-01-23 14:47
Optimus

Registered: Jan 2002
Posts: 122
How are some effects done?

I hope this doesn't sound stupid.

There are few effects that make me wonder today. Perhaps I still miss a lot about the C64. One of them is the several DYCP scrollers blended all together as seen in Royal Arte. I ask out of curiosity because it still makes me wonder..

Ok, there must be hardware horizontal scrolling involved of course, to the left. But it seems like all letters have to be updated all over the screen each frame. If there were data written just in the right side of the screen and then the whole chars moved to the left, it would seem static. Now I see the letters of each scrollie moving in a diferrent manner in every row independently on the screen as they are independent sprites each other. It seems to me like a huge ammount of the screen has to be updated per frame, which doesn't seem very possible to me. Or is there a simple trick/illusion in there that I haven't grasped?

p.s. If I remember some other C64 effects that made me really wonder, I may ask more here.
 
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2006-01-27 08:36
Style
Account closed

Registered: Jan 2002
Posts: 17
Oh no, now youve gone and done it - Im interested in how it is done!

I can feel a mega DYCP part coming on for our oldschool demo - noone mention any other old effects goddam it! :)
2006-01-27 09:58
Cruzer

Registered: Dec 2001
Posts: 1051
DYSP, DYPP, DXYCP, rastersplits, techtecher, floffy, rubbervector... :P
2006-01-27 10:33
Graham
Account closed

Registered: Dec 2002
Posts: 990
Clarence already did the perfect DYPP, nothing to add to that :P
2006-01-27 10:49
TDJ

Registered: Dec 2001
Posts: 1879
Quote: Oh no, now youve gone and done it - Im interested in how it is done!

I can feel a mega DYCP part coming on for our oldschool demo - noone mention any other old effects goddam it! :)


Smoothie scroll.

That's right: smoothie scroll. A scroll with no hair whatsoever.
2006-01-27 10:57
Steppe

Registered: Jan 2002
Posts: 1510
Smooth scrolling in Vice is impossible! :D
2006-01-27 11:04
WVL

Registered: Mar 2002
Posts: 924
Quote: graham: you are assuming that 32 preshifted chars is impossible because 32 x 8 x 2 = 512 chars.

However, remember that with the right charset, you might be able to get it down to below 256 since, for example, the top of an 'I' looks like the top of a 'T' and a 'J', the top of an 'F' looks like the top of an 'E', the bottom of an 'E' looks like the bottom of an 'L' etc etc etc

Remember, you only need the distinct chars, not literally every letter preshifted 8 times across 2 chars.

If you can achieve that, multiple DYCPs becomes a problem of collision detection. Depending on how many there are you might need more chars leftover in the charset to ORA the colliding chars, or you could even use sprites I guess.



exactly what i said ;)

but if you're charset is only 5 pixels high, you don't even need (different letters)*8*2 chars, but only (different letters)*(4+8), since 4 'shifts' will fit in 1 char, and the other 4 would need 2 chars to fit into..

32 chars charset results into 384 chars needed.. now i think it's really easy to remove all double used from that to get below 230 or so..
2006-01-27 11:54
HCL

Registered: Feb 2003
Posts: 731
Quote: Clarence already did the perfect DYPP, nothing to add to that :P

Oh, i think i have something to add then..
2006-01-27 12:09
WVL

Registered: Mar 2002
Posts: 924
Quote: Oh, i think i have something to add then..

I think HCL did the perfect 15 DYCP.. nothing to add then.. ;)
2006-01-27 12:37
Cruzer

Registered: Dec 2001
Posts: 1051
Quote: Clarence already did the perfect DYPP, nothing to add to that :P

Yes, but we need 15 MEGADYPPs like that.
2006-01-27 13:17
Optimus

Registered: Jan 2002
Posts: 122
Well, thanks! I think I got a clue from the first posts.

At first I never thought this effect could be achieved by LDA STA codes and some trickery, I hadn't noticed there is something static in it that just scrolls fast to the left (well yes, a friend noticed it by focusing more closely to the screen ;). I was thinking it the very regular way, where you have to draw softsprites on the screen and find the screen ram positions for each letter out there in realtime. But with static positions, sliding the letters through these, pregenerated codes, and the cycle calculations mentioned here I understood it's preety possible. Wow!

Yesterday night, I was thinking it again and also figured out how some effects on the CPC are done that fast via a similar way. You know, I need such coder's talk to get inspiration for my CPC democoding too :)

Nice to see that this evolved into a coder's discussion..
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