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Post by Pyrofer on Apr 11, 2016 19:12:57 GMT
It's possible to stop the flicker. You need a decent interrupt loop setup linked to vblank to time when to do the reset of the smooth scroll register.
I have a whole screen of colour bitmap scrolling down the screen and depending on when I start the scrolling I get none, some or all flicker.
When there is none it looks lovely. I need to experiment with exactly what the timing needs to be in relation to vblank so I can consistently get no flicker.
I think I am confident it's possible though. BTW, whole screen scrolling in colour bitmap.
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Post by hydrophilic on Apr 14, 2016 8:23:05 GMT
Cool... weather text or bitmap, if you can publish results of WHEN to update scroll-register to avoid flicker, the entire C128 community will thank you (at least me).
In other words, I agree the problem is when... EXACTLY... you need to update the register(s)...
I also agree it will (probably) be a PITA because there is no hardware interrupt, or even a simple raster register... you will have to laboriously track the V-Blank bit (simple, but time consuming), or else sync a CIA timer with the VDC (more work to setup, but less CPU resources). I think most of know that Risen From Oblivion uses CIA sync'd to VDC (so a good place to start)...
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Post by remark on Apr 17, 2016 17:59:20 GMT
I played with the colorscroll v2.5 program a little. The 'flicker' only occurs if you put the text in line 1 of the screen, in lines 2-25 the scroll is smooth as expected. My guess is there is too little time between vsync and display of the first line, to both copy the screen data and color data. (16k PAL VDC)
EDIT: hm, if you display 2 lines of text, the first line is flickering, the second is not. So probably a 'hardware' bug of the VDC?
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Post by Pyrofer on Apr 19, 2016 10:33:06 GMT
Tokra has proven that we are indeed all idiots in some way.
His smooth scrolling test demo indeed works flawlessly in VICE (Not tried on real hardware yet).
I am going to have to go through his code and mine line by line working out where the differences come. I really wan't to find the reason that mine flickers as honestly, I can't see it.
I assume that this scrolling text demo flickers for the exact same reason as my vertical scroller does so when we lock down the reason everybody who wants to play with the VDC can benefit from it.
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Post by remark on Apr 11, 2017 19:12:18 GMT
Sorry to stir this thread up, but I think have a solution against the flickering. You need to start the copy when smooth=1 instead of 0. VDCADR = $d600
VDCDAT = $D601
TxtPtr = $a9
ClrPtr = $96
smooth = $ab
color = $a8
defm poke
lda #/2
sta /1
endm
defm WaitVDC
bit $d600
bpl *-3
endm
*=$1c01
Byte $11,$1c,$de,$07,$de,$9c,$3a
byte $fe,$25,$3a,$9e,$37,$31,$38,$37
bytes $00*3
;2014 graphicclr:fast:sys7187 in basic
Start Poke smooth, $07
poke color, $08
ldx #$18
jsr VdcPeekReg
ora #$80 ;set copy bit
sta VDCDAT
jsr zp0 ;set up pointers
MainLoop lda #$20 ;bit 5 we checking
bit vdcadr ;wait for vblank
beq *-3
sei ;don't want to be interupted
jsr scroll
ldx #$19
jsr VDCPEEKREG
and #%11110000
ora smooth
sta vdcdat ;scroll left
cli ;done so release interupts
lda #$20
bit vdcadr
bne *-3 ;wait for the start of the frame
jmp MAINLOOP
scroll lda smooth
sec
sbc #$01 ;use 1 only (need different loop to slow down)
; bcc MoveText
cmp #1
beq MoveText
cmp #0
bne scend
lda #7
scend sta smooth
rts
;MoveText lda #$07
; sta smooth
MoveText ldy #$00
lda (txtptr),y
cmp #$ff
bne @nopeff
jsr zp0
lda (txtptr),y
@nopeff cmp #$fe
bne @nopefe
lda (clrptr),y
sta color
jsr incclrptr
jsr inctxtptr
lda (txtptr),y
@nopefe jsr inctxtptr
pha
ldy #$20 ;reg pair
lda #$00 ;high byte
ldx #$01 ;low byte
jsr vdcwordreg
ldy #$12
lda #$00
ldx #$00
jsr vdcwordreg
ldx #$1e
lda #$4f ;copy 79 bytes
jsr VdcPokeReg
pla
ldx #$1f
jsr VDCPOKEREG
ldy #$20 ;color source
lda #$08
ldx #$01
jsr vdcwordreg
ldy #$12 ;color destination
lda #$08
ldx #$00
jsr vdcwordreg
ldx #$1e ;copy 79 bytes
lda #$4f
jsr vdcpokereg
ldx #$1f
lda color
jsr vdcpokereg
rts
zp0 lda #<ScrollText
sta TxtPtr
lda #>Scrolltext
sta TxtPtr+1
lda #<Colordata
sta CLRPTR
lda #>ColorData
sta CLRPTR+1
rts
VdcPokeReg stx vdcadr
waitvdc
sta vdcdat
rts
VdcPeekREG stx vdcadr ;.x reg and value returned in .a
waitvdc
lda vdcdat
rts
VDCWordreg sty vdcadr ;a/x is high/low value y is high byte of reg pair
waitvdc
sta vdcdat
iny
sty vdcadr
stx vdcdat
rts
IncTxtPtr inc TXTPTR
bne @end
inc TXTPTR+1
@end rts
IncClrPtr inc clrptr
bne @end
inc clrptr+1
@end rts
ScrollText byte $fe
text 'this is a test of '
byte $fe
text 'the '
byte $fe
text 'scrolling demo... '
byte $fe
text 'flash '
byte $fe
text 'underline '
byte $fe
text 'reverse '
byte $fe
text 'charSET '
byte $ff
ColorData byte $0f,$0d,$0c,$1c,$2c,$4a,$86I changed and added some lines in the scroll and movetext subroutines. This will get rid of the flickering in the first line. colscroll25a.prg (351 B) |
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Post by tokra on Apr 24, 2017 16:21:48 GMT
Very nice! So by combining both horizontal and vertical scrolling you could easily move around the screen in all directions, which might come in handy for some games.
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Post by Pyrofer on Apr 24, 2017 16:50:31 GMT
I did actually get vertical smooth scrolling working. I still haven't managed to do the same with Horizontal however. I might get back into trying to make a game with scrolling colour bitmap mode  |
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