-----Original Message-----
From: "Eckhard Stolberg" <Eckhard_Stolberg@xxxxxx>
To: <stella@xxxxxxxxxxx>
Date: Sat, 26 Jul 2003 14:55:08 +0200
Subject: Re: [stella] VDELP problem
> > I have a problem with the damn VDELP.
> >
> > When use only VDELP0 all is just perfect!
> > But after adding VDELP1 I have following troubles:
> > P0 and P1 sprites are showed interlaced (when they are on the same
> scanline). I have the feeling that VDELP0 and VDELP1 use the same additional
> buffer register.
> >
>
> No, there are individual buffer registers for GRP0 and GRP1, but
> how they are written to isn't explaind that well in the Stella
> programmers guide.
>
[skipped]
>
> Ciao, Eckhard Stolberg
>
Thanks a lot! I've got the idea. Actually I don't care about single line movement resolution, because my goal was saving some extra cycles by not using player buffer. But now it seems that there will be no optimization (or even worse), because I'll have to change some code and waste some cycles.
Now about optimization. Currently I use the following code for displaying sprites and other objects (it includes the checking of range, where the entity is visible).
---code begins here
; calc current PF's graphics line (div by 4)
LDA ScanLine ; 3
CLC ; 2
ADC PFRY ; 3
LSR ; 2
LSR ; 2
TAY ; 2
LDA (PFPtr0),Y ; 5
; = 21 = 145
; start new scanline
STA PF0 ; 3 set PF graphics
LDA EnemyBuff ; 3 set enemy's graph
STA GRP1 ; 3
LDA ObjBuff ; 3 set obj's graph
STA ENABL ; 3
LDA (PFPtr1),Y ; 5
STA PF1 ; 3 = 23
LDA (PFPtr2),Y ; 5
STA PF2 ; 3 = 26 set remaining PF graph
; prepare P0 graphics for the next scanline
CheckP0_0
LDA #0 ; 2
STA ObjBuff ; 3 zero out object's buffer
LDX ScanLine ; 3 = 37
PrepareP0Graph_0
CPX P0RY ; 3 P0RY contains the upper coord
BCS Waste1_27 ; 2
CPX Temp4 ; 3 contains lower coord
BMI Waste1_22 ; 2
; C is always set here
LDA P0RY ; 3
SBC ScanLine ; 3
TAY ; 2
LDA (P0GrPtr),Y ; 5
STA GRP0 ; 3
LDA P0Colors-1,Y ; 4
STA COLUP0 ; 3
; = 33 = 69
FinishP0_0
PrepareP1Graph_0
CPX EnemyRY ; 3
BCS Waste2_27 ; 2
CPX Temp3 ; 3
BMI Waste2_22 ; 2
; C is always set here
LDA EnemyRY ; 3
SBC ScanLine ; 3
TAY ; 2
LDA (EnemyGrPtr),Y ; 5
STA EnemyBuff ; 3
LDA EnemyColors-1,Y ; 4
STA COLUP1 ; 3
; = 33 = 101
FinishP1_0
PrepareBLGraph_0
CPX ObjRY ; 3
BCS Waste3_14 ; 2
CPX Temp5 ; 3
BMI Waste3_9 ; 2
LDA #M_Enable ; 2
STA ObjBuff ; 3
DEC ScanLine ; 5
; = 20 = 118
FinishBL_0
Finish_0
NOP
STA Temp ; 5 cycles available
BNE MainParScanLoop ; 3 next scanline
; = 126
JMP FinishScanLoop ; 6
Does anyone know if it is possible to optimize this? Maybe there are other methods to check if the entity must be shown?
PS. I used to use line counters which were decremented every time another line had been shawn. This method have some disadvantages.
>From Russia with love!
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