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Forums > C64 Coding > Double buffering color ram in half of the screen?
2017-10-18 11:52
Color Bar

Registered: Oct 2012
Posts: 138
Double buffering color ram in half of the screen?

Suppose you have some text or MC bitmap graphics only in the bottom half of the screen, perhaps you could double buffer (color ram & gfx) using FLD?

I mean: in one frame you first switch to an empty screen in the top half (where you have some sprite action, say) and in the bottom half you switch to the desired graphics screen. In another frame you FLD the top half of desired color ram & gfx down to the bottom half.

Don't know if this can be useful though.
 
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2017-10-18 19:09
Groepaz

Registered: Dec 2001
Posts: 8408
actually the idea is even older... some other guy came up with a japanese-style bullet-hell shooter like thingy which used this technique and posted it here on csdb even more years before. too bad i totally forgot the name of the guy or the production (maybe someone else remembers?)
2017-10-18 19:10
Krill

Registered: Apr 2002
Posts: 932
And there are more benefits, beyond technical advantages: there are 256 freely-positionable double-height tiles (8x16 or 4x16 pixels), which is (almost) double as much graphics to play with for a graphician/level designer. :)
2017-10-18 21:09
ChristopherJam

Registered: Aug 2004
Posts: 746
Quote: actually the idea is even older... some other guy came up with a japanese-style bullet-hell shooter like thingy which used this technique and posted it here on csdb even more years before. too bad i totally forgot the name of the guy or the production (maybe someone else remembers?)

That was Doynax's Balls of the Scrolling Thunder; he commented extensively about it in the Sorting discussion ten years ago.
2017-10-18 21:38
Groepaz

Registered: Dec 2001
Posts: 8408
mmmh but where is it then? pretty sure it had a csdb entry too.... *shrug*
2017-10-18 21:40
ChristopherJam

Registered: Aug 2004
Posts: 746
Never completed to my knowledge.
2017-10-18 21:41
Groepaz

Registered: Dec 2001
Posts: 8408
no, but binary posted and added as "preview". i certainly have run it myself :)

edit: Balls of Scrolling Thunder Preview
2017-10-19 00:09
Color Bar

Registered: Oct 2012
Posts: 138
Quote: That was Doynax's Balls of the Scrolling Thunder; he commented extensively about it in the Sorting discussion ten years ago.

Quoting doynax
The d800 copy is double buffered and evenly distributed across 16 frames, so it really doesn't take much raster time at all ;)

Yes, I remember having seen this, but how does he do it? With linecrunching or FLD?
2017-10-19 00:16
Groepaz

Registered: Dec 2001
Posts: 8408
in one frame, push down the screen 12(?*) (raster)lines using FLD, then create 12 doubled (character)lines. in the second frame crunch the first 12(?*) lines and then create 12 doubled lines.

(*) not sure if that is the optimum if you also want to do vertical scrolling
2017-10-19 02:51
Skate

Registered: Jul 2003
Posts: 470
if anyone interested in original version of the Doynax's game, there you go.

http://www.akaydin.com/c64/stuff/Balls_of_the_Scrolling_Thunder..
2017-10-19 03:05
Groepaz

Registered: Dec 2001
Posts: 8408
Balls of the Scrolling Thunder (Preview) :)
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