Re: [stella] Game project

Subject: Re: [stella] Game project
From: Eckhard Stolberg <Eckhard_Stolberg@xxxxxxxxxxxxxxxxxxxxx>
Date: Fri, 19 Jun 1998 15:28:51 +0200
At 21:17 18.06.98 -0400, you wrote:

>can be either on or off (1 or 0). The problem is : although everything
>is just one color, the playfield graphics must be either reflected or
>repeated, which is really not what I want :) I anyone knows how to do it
>(I think it involves changing the data in the middle of the scanline),
>then I would like to know how. Also, I want to know if it is possible to

You have to set the playfield to repeated. For every scanline do:
STA Wsync
fill the three playfield registers with the left data
wait untill PF0 has been drawn, but before PF0 will be redrawn
store right data in PF0
wait untill PF1 has been drawn, but before PF1 will be redrawn
store right data in PF1
wait untill PF2 has been drawn, but before PF2 will be redrawn
store right data in PF2
loop back

An example:
L1: sta WSYNC
    lda field0-L,y    ;4
    sta PF0           ;7
    lda field1-L,y    ;11
    sta PF1           ;14
    lda field2-L,y    ;18
    sta PF2           ;21
    lda field0-R,y    ;25
    sta PF0           ;28
    nop               ;30
    nop               ;32
    lda field1-R,y    ;36
    sta PF1           ;39
    nop               ;41 
    nop               ;43
    lda field2-R,y    ;47
    sta PF2           ;50
    dey
    bpl L1

>move a sprite more than 8 units either left or right between each frame
>(like at frame 1, it's at position x=0, and frame 2, it's at position
>x=120)...

Erik Mooney has posted a routine for that with lots of comments
in April. You can find it in the archive.


Ciao, Eckhard Stolberg



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