Displaying sprites

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Revision as of 13:40, 14 March 2012 by ElBarto (talk | contribs)
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How to display a 64*80 (4*5 tiles) sprite block at x=88, y=36.

Loading palette

At least one palette needs to be loaded. Here SpritePalette is loaded as palette 0 and the backdrop color is set to black.

    lea     SpritePalette,a0
    lea     PALETTES,a1
    moveq.l #16-1,d0
    move.w  (a0)+,(a1)+
    dbra    .ldpal


Setting the map

The sprite's map is an array of tile numbers and attributes. Here the 4 sprites are made of tiles 0~4 with no special attributes.

    move.w  #64,d2          ;SCB1, sprite 1
    move.w  #1,VRAM_MOD
    moveq.l #4-1,d6
    move.w  d2,VRAM_ADDR
    clr.w   d1              ;First tile is #0
    moveq.l #5-1,d7
    move.w  d1,VRAM_RW      ;Tile number
    move.w  #0,VRAM_RW      ;No attributes
    addq.b  #1,d1
    dbra    d7,.tiles
    addi.w  #64,d2          ;Next sprite
    dbra    d6,.sprites

Setting the shrinking

No shrinking at all (full size).

    move.w  #SCB2+1,VRAM_ADDR
    moveq.l #4-1,d7
    move.w  #$0FFF,VRAM_RW
    dbra    d7,.zset

Setting the size and vertical position

First sprite is the driving one, next are driven.

    move.w  #SCB3+1,VRAM_ADDR
    move.w  #((496-36)<<7)+5,VRAM_RW ;Y position and size for the first sprite
    moveq.l #5-1-1,d7
    move.w  #64,VRAM_RW   ;Sticky bit only for the 3 others
    dbra    d7,.yset

Setting the horizontal position

    move.w  #SCB4+1,VRAM_ADDR
    move.w  #88<<7,VRAM_RW