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Flavioweb
Registered: Nov 2011
Posts: 122 |
Sprites over rasterbars: where?
Someone can tell me a demo/intro name where are sprites movin' over rasterbars?
Or, at least, sprites without movement over rasterbars?
Tnx. |
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Flavioweb
Registered: Nov 2011
Posts: 122 |
Quoting SkateThere are many. I leave others to give you examples. But i will try to give you the main idea about sprites with rasterbars.
I hope you were looking for the techniques. I thought it's better this way than examining the codes. If you just needed the demo names, you can forget about my answer. :)
Yes, i want to know "how things works".
I don't start this thread into "coding" section, because i don't know how many people want to share his knowledge, but if someone want to help me into learning how to do sprites moving over rasterbars... any help is welcome...
Maybe some moderator will change thread section =) |
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Codey
Registered: Oct 2005
Posts: 75 |
also if you use fld for your timing, your rasters will be perfect and can have sprites moving over them iirc. the only drawback is no char mode.. |
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Flavioweb
Registered: Nov 2011
Posts: 122 |
Quoting PeiselulliMaybe look into Jars's Revenge ingame code ... there are no rasterbars, but the border is disabled (which is more time critical) with moving sprites ...
At a first look, seems that is used a stable irq (inverted timer) with code for every line unrolled, and jitter is compensated "on the fly" when -cycles- goes on new raster line...
I'm on right path?
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Graham
Registered: Dec 2002
Posts: 969 |
Real DYSP |
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iAN CooG
Registered: May 2002
Posts: 1158 |
Dingy
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Zaz
Registered: Mar 2004
Posts: 26 |
This Is What It Is |
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ready.
Registered: Feb 2003
Posts: 388 |
a part of this demo:
20 Minutes in the Future |
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raven
Registered: Jan 2002
Posts: 129 |
Continuing what Skate has started, there's a 3rd method which is easiest to implement & also most versatile, as it basically takes care of itself.
Use a timer to count down from 63 and branch according to its value. This code must be done each line.
If you'd like bad-lines active, they'll require different handling.
The line code will look something like this:
lda #cycles
sbc $dd04
sta *+4
bcs *
lda #$a9
lda #$a9
...
bit $ea
...rest of raster code...
+ Sprites can be moved freely without restrictions, no update of the timings is required for non bad-lines
- Doesn't leave much raster-time per line |
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Trash
Registered: Jan 2002
Posts: 52 |
Another simple solution if you dont want graphics behind the sprites is:
outer_loop:
lda #raster_row
ldx #count_rows
cmp $d012
bne * - 3
inner_loop:
lda coltable, x
sta $d020
sta $d021
lda $d011
and #7
ora #16
sta $d011
dex
bne inner_loop
; move sprites around here
jmp outer_loop |
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Oswald
Registered: Apr 2002
Posts: 3146 |
or you can do it as Ninja, set a CIA timer to count down from 63 & set the irq vector over the CIA timer & set the register before to jump instruction $4c, and it will select the routine needed for the desired timing automagically. Beware, this eplanation is very rough, just added to drop in the idea. |
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