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2011-11-08 22:29

Cobrakid

Registered: Oct 2011
Posts: 23

Mixing multiple effects is messing up stuff

I am doing a small and very lowtech demo but I seem to be confused about the raster timing - probably like any other C64 newbie out there(?).

I know(?) this is related to the raster interrupt I am using plus my routines and that everyone will shout out "learn to code before you do a demo" and you are right but I really need some directions or hints here as I cannot get my head around this problem. I have read a lot on the C64 Codebase and here in the forum but still I don't get it (no hope for me!?).

I am trying to get a static (not moving) rasterbar below a 2x2 scroll plus some music - this must be "demo programming day 1". I have done each part individually and they work but together they are screwing up things (of course!?). Well, the music and the 2x2 scroll I can get working but introducing the raster gets ne problems.

What I have is a rasterbar... fired up at raster pos #$80 (as an example). A few lines below I am starting my scroll and this is totally messing up things... the scroll is veeery slow and shifting between the 2x2 charset and the system charset and when playing music I can hear it is slowing down to 1/4 of the normal pace or alike. This must be because the rasters are overlapping but how can I overcome this?

This is not a matter of getting the rasterbars looking nice but a more fundamental problem I think - then the prettyness of the bars will be a problem for later on.

If anyone would explain me how or point me to a fool-proof-dummy-guide on how I might can solve this I would really appreciate it as I am getting really frustrated now and I don't see any solutions for it (though there obvioulsy is one).

... 21 posts hidden. Click here to view all posts....

2011-11-10 15:22

Cobrakid

Registered: Oct 2011
Posts: 23

@Frantic and ready - thanks for the links.

I have just tried doing the most simple piece of code - with two interrupts and flashing the border. There I can trigger the "sta $d019" so I must (naturally) be doing something wrong in my other part but I cannot see what.

What I still don't get is when something takes (for example) 50 raster lines (as seen with flashing $d020) and I need to place something else in that area (for example a scroll in front of a rasterbar)... how the h... is this done correctly with IRQ?

If you see this picture:
http://cobrakid.dk/asm/mydmo5.png

The yellow is the raster time for the rasterbar and the green is for the splitscreen for the scroll.

I cannot get this working in a way which I understand (currently I don't ACK the IRQ in my first interrupt - see previously posted code). I would appreciate some phseudo code or alike to get it right?

2011-11-10 15:36

Oswald

Registered: Apr 2002
Posts: 5094

the problem is you dont have the basic understanding of what a(n raster) interrupt is, how the screen is drawn and how it is timed with the cpu, whats is drawn with the help of the cpu / gfx chip. You dont see the whole picture only some very small fragments of it.

for example, placing a scroller in front of a rasterbar is no problem, because you D O N ' T need any timing / raster irqs to do that. You simply set up the screen memory and the video chip will display the scroller, you dont need timed raster irqs to do that ! ! !

You have to start out with very basic stuff and experiment. Do the scroller / rasterbar individually first, understand them fully, then put them together, etc.

2011-11-10 15:38

ready.

Registered: Feb 2003
Posts: 441

for the effect you want, you need only 1 IRQ that triggers always at raster $70 (not #70!!! # means it's a number and not an address in assembly code, $ means it's hexadecimal).

So the steps you need are:

- enter IRQ at raster $70
- set screen x position ($d016 bits 0,1,2)
- change $d020/$d021 for raster bars until line $80+$16
- exit IRQ

then inside the background program (outside IRQ) you do the scrolling and prepare the screen position (written inside the IRQ to $d016). Don't do the scrolling in the IRQ. Now your background program is just "jmp *"

2011-11-10 15:40

Oswald

Registered: Apr 2002
Posts: 5094

pseudocode for your Q:

raster irq starts:

-> setup X fine scroll
for x=0 to number of lines
get rastercolor: poke $d020, rastercolor: poke $d021, rastercolor
next x
-> reset X fine scroll to default value
-> redraw scroller
-> play music

raster irq stops.

2011-11-10 15:42

Oswald

Registered: Apr 2002
Posts: 5094

Quote: for the effect you want, you need only 1 IRQ that triggers always at raster $70 (not #70!!! # means it's a number and not an address in assembly code, $ means it's hexadecimal).

So the steps you need are:

- enter IRQ at raster $70
- set screen x position ($d016 bits 0,1,2)
- change $d020/$d021 for raster bars until line $80+$16
- exit IRQ

then inside the background program (outside IRQ) you do the scrolling and prepare the screen position (written inside the IRQ to $d016). Don't do the scrolling in the IRQ. Now your background program is just "jmp *"

No. Do the scroller _IN_ the irq, after the rasterbars have been drawn. Some stuff are timing critical, some are not. Doing the scroller is not timing critical, but you have to do it once per frame exactly, so simply you execute it after having draw the rasters.

2011-11-10 15:50

Cobrakid

Registered: Oct 2011
Posts: 23

But Oswald - how do I then setup the splitscreen? This splitscreen has to be within the rasterbar area!?

I do want a splitscreen as I am getting another 1x1 scroll or maybe some text in the top.

2011-11-10 16:19

Cobrakid

Registered: Oct 2011
Posts: 23

@ready - THIS I get... of course... it is so simple. As I don't care for other characters in the rasterbar I just start the splitscreen the same time as the rasterbar starts... and end it afterwards.

That was simple (and I have fixed it). I need to tweak it for a badline but I know how to do that (hmmm.. my method with x number of "bit $ff").

Well, in my case the problem was not the technical part... hmmm OK, it was that too, but it was the "ahhhhhh" I got from seeing your phseudo code that solved it and I guess I am just not meant for being a programmer since I had a much more complex approach for doing this.

Thanks (all) for your help. I suspect I will write again some day (maybe sooner than I hope) :-)

BTW @ready - I do know the diff on #70 and $#70 ;-) It is completely diff positions (line 70 vs 112).

2011-11-10 19:01

Cobrakid

Registered: Oct 2011
Posts: 23

Just a followup on this one - the code can be seen here, http://cobrakid.dk/asm/mydmo5-asm.txt. Maybe someone else can benefit from it.
I am not too proud of this one (in the start if the IRQ):

; Prevent badline (by having
; bad code!? Hmmm...)
; This is the only(?) part
; which I do not fully
; understand - why cant this
; part be in the setup irq?
bit $ff    ; 3 cycles
bit $ff    ; 3 cycles
bit $ff    ; 3 cycles
bit $ff    ; 3 cycles
nop        ; 2 cycles
nop        ; 2 cycles

It clearly states I am not in full control but I hope to get there - I need to study more and maybe even ask a few questions here yet.

2011-11-10 19:06

tlr

Registered: Sep 2003
Posts: 1790

The irq always triggers when the raster counter changes. You cannot alter that by "setting up" the raster irq differently so if you need a different starting point in the raster line you have to add a delay like you do.

There are ways to do it more compact though. Consider jsr-ing directly to an rts for wasting 12 cycles for instance.

2011-11-10 23:48

Stainless Steel

Registered: Mar 2003
Posts: 966

I'm really not an expert, but i took the liberty to modify your code a bit. how about this :

(ACME format. Rasterbar timingtable unfixed. Also this is is not the best way to do things but it works. Note for the wiseguys : yeah $d012 polling is slow and all but its an easier concept to grasp for beginners i think)

!TO "test.prg"

*=$0ffe
!BIN "tune.dat"

scrltxt = $5000

*= $4000

jsr $e544
sei
lda #$01
sta $d01a
lda #$7f
sta $dc0d
lda #<split1
sta $0314
lda #>split1
sta $0315
cli
ldx #$00
jsr $1000
jmp *

split1
lda #$00
cmp $d012
bne *-3
lda #$00
sta $d020
sta $d021

split2
lda #$7a
cmp $d012
bne *-3

lda #$15
sta $d018

lda smooth ; move the scroll
sta $d016 ; to the left dep.
; on the smooth-bit

jsr raster ; draw the rasterbar

split3
lda #$9d
cmp $d012
bne *-3

dec $d020 ;<- visualize rasterusage
jsr scroll2x2 ; print the
; scrolltext
inc $d020 ;<- visualize rasterusage

lda #$08 ; set normal
sta $d016 ; screen

split4
lda #$c0
cmp $d012
bne *-3
lda #$03
sta $d020
sta $d021

dec $d020 ;<- visualize rasterusage
jsr $1003
inc $d020 ;<- visualize rasterusage

inc $d019
jmp $ea31

; ======================================

scrspeed !byte $02 ; speed of scr.(1-8)
smooth !byte $07 ; smooth bit
half !byte $02
char !byte $00

scroll2x2
; ---------------------------
; Routine mostly from Ghouls
; Maskinkode Kursus as seen
; on CSDb (release id=8646)
; ---------------------------

lda smooth
sec
sbc scrspeed ; substract speed
and #$07 ; AND it with 7
; to get the
; smooth effect
sta smooth ; save the new
; smooth val
bcs quit ; quit the scroll
; if we dont need
; to update the
; screen

ldy #$00 ; black text color
ldx #$00
repeat1 lda $0401+(10*40),x ; move the
sta $0400+(10*40),x ; two lines
lda $0401+(11*40),x ; one to
sta $0400+(11*40),x ; the left
tya
sta $d800+(10*40),x ; set char
sta $d800+(11*40),x ; color
inx
cpx #39 ; move 39 chars
bne repeat1

; ---
; Only put a new char from the
; scrolltxt on the screen for
; every second frame/move
dec half
bne rolltxt ; jump to display
; a new char if
; we have ended
; the 2nd half of
; this char
lda #$02 ; reset the val
sta half ; that tells if
; this is the 2nd
; half of the
; char
lda char ; get the char
; that we are
; working on
ora #$40 ; shift it
sta $0400+(10*40)+39 ; and dis-
; play it
; on the
; 1st line
ora #$80 ; invert
sta $0400+(11*40)+39 ; it and
; display
; on 2nd
jmp quit

; ---
; Display a new char from the
; scrolltxt - it will only show
; the 1st half of the char
rolltxt lda scrltxt ; read next char
cmp #$00 ; stopchar? "@"
bne nextchar ; if not then jmp

lda #<scrltxt ; restart scroll
sta rolltxt+1
lda #>scrltxt
sta rolltxt+2
jmp rolltxt ; continue scroll

nextchar sta $0400+(10*40)+39 ; print
; the next char in the raster
; border (pos 39) on both lines
sta char ; set the working
; char
ora #$80 ; invert it
sta $0400+(11*40)+39

inc rolltxt+1 ; incr the scrtxt
; addr (low-byte)
bne quit
inc rolltxt+2 ; incr the scrtxt
; if it is longer
; than 256 bytes

quit rts ; return to my irq

; ======================================

raster
; Fine-tune raster position
; to avoid flickers
nop
nop
nop
nop
nop

ldx #0
loopcol lda colors,x
sta $d020
sta $d021
ldy delays,x
loopdel dey
bne loopdel
inx
cpx #numcols
bne loopcol

lda #$00
sta $d020
sta $d021

rts

; ----------------------------

indexcol !BYTE $00
numcols = 33

*= $5a00
colors
!BYTE $0a,$02,$0a,$0a,$0a,$07
!BYTE $0a,$00
!BYTE $07,$0a,$07,$07,$07,$0d
!BYTE $07,$00
!BYTE $0d,$07,$0d,$0d,$0d,$03
!BYTE $0d,$00
!BYTE $03,$0d,$03,$03,$03,$00
!BYTE $03,$00
!BYTE $00,$00,$00,$00,$00,$00
!BYTE $00,$00
!BYTE $00,$00,$00,$00,$00,$00
!BYTE $00,$00
!BYTE $01,$00,$00,$00,$00,$00
!BYTE $00,$00
!BYTE $00,$00,$01

*= $5b00
delays !BYTE $08,$08,$08,$08,$08,$08
!BYTE $08,$01
!BYTE $08,$08,$08,$08,$08,$08
!BYTE $08,$01
!BYTE $08,$08,$08,$08,$08,$08
!BYTE $08,$01
!BYTE $08,$08,$08,$08,$08,$08
!BYTE $08,$01
!BYTE $08,$08,$08,$08,$08,$08
!BYTE $08,$01
!BYTE $08,$08,$08,$08,$08,$08
!BYTE $08,$01
!BYTE $08,$08,$08,$08,$08,$08
!BYTE $08,$01
!BYTE $08,$08,$08

; ============================

scrolltext
*=$5000
!SCR "hi i am a scrolltext"

Oh yeah and you wont get the jitters away with this easily. Use delays where necessary to move them out of visual areas.

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