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sprites.asm
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sprites.asm
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*=* "Sprite Routines"
//
// These routines can be used to move and manipulate the sprites on the 64.
//
#if REGISTER_MODE
//
// Position a sprite anywhere on the screen
// This variant uses hardware registers instead of pseudo registers
//
// X sprite number (0-7)
// A,Y x pos (0-319)
// $02 y pos (0-199)
//
PositionSprite:
pha
tya
pha
txa
mult2
tay
lda $02
sta vic.SP0Y, y
pla
sta $02
pla
sta r6L
lda $02
adc #$00
sta r6H
stb r6L:vic.SP0X, y
ldx r3L
lda BitMaskPow2, x
eor #$ff
and vic.MSIGX
tay
lda #$01
and r6H
beq !no_msb+
tya
ora BitMaskPow2, x
tay
!no_msb:
sty vic.MSIGX
!return:
rts
//
// Change one of a sprite's attributes
// This variant uses hardware registers instead of pseudo registers
//
// X sprite number (0-7)
// Y attribute to change (SPR_VISIBLE, SPR_X_EXPAND, SPR_Y_EXPAND, SPR_HMC, SPR_PRIORITY)
// A value for the attribute
// - Sprite visibility (SPR_SHOW, SPR_HIDE)
// - X/Y expansion (SPR_NORMAL, SPR_EXPAND)
// - Priority (SPR_FG, SPR_BG)
// - Hires or Multicolor (SPR_HIRES, SPR_MULTICOLOR)
//
ChangeSpriteAttribute:
pha
lda BitMaskPow2, x
sta $02
pla
tax
lda $02
cpx #ENABLE
beq !set_flag+
eor #$ff
and vic.SP0X, y
jmp !clear_flag+
!set_flag:
ora vic.SP0X, y
!clear_flag:
sta vic.SP0X, y
rts
#else
//
// Position a sprite anywhere on the screen
// This variant uses the zeropage pseudo registers, which may not be compatible with BASIC or the Kernal
//
// r3L sprite number (0-7)
// r4 x pos (0-319)
// r5L y pos (0-199)
//
PositionSprite:
lda r3L
mult2
tay
stb r5L:vic.SP0Y, y
stb r4L:r6L
lda r4H
adc #$00
sta r6H
stb r6L:vic.SP0X, y
ldx r3L
lda BitMaskPow2, x
eor #$ff
and vic.MSIGX
tay
lda #$01
and r6H
beq !no_msb+
tya
ora BitMaskPow2, x
tay
!no_msb:
sty vic.MSIGX
!return:
rts
//
// Change one of a sprite's attributes
// This variant uses the zeropage pseudo registers, which may not be compatible with BASIC or the Kernal
//
// r3L sprite number (0-7)
// r3H attribute to change (SPR_VISIBLE, SPR_X_EXPAND, SPR_Y_EXPAND, SPR_HMC, SPR_PRIORITY)
// r4L value for the attribute
// - Sprite visibility (SPR_SHOW, SPR_HIDE)
// - X/Y expansion (SPR_NORMAL, SPR_EXPAND)
// - Priority (SPR_FG, SPR_BG)
// - Hires or Multicolor (SPR_HIRES, SPR_MULTICOLOR)
//
ChangeSpriteAttribute:
ldy r3H
ldx r3L
lda BitMaskPow2, x
ldx r4L
cpx #ENABLE
beq !set_flag+
eor #$ff
and vic.SP0X, y
jmp !clear_flag+
!set_flag:
ora vic.SP0X, y
!clear_flag:
sta vic.SP0X, y
rts
#endif
//
// This allows us to translate sprite numbers into bit masks
//
BitMaskPow2:
.byte %00000001
.byte %00000010
.byte %00000100
.byte %00001000
.byte %00010000
.byte %00100000
.byte %01000000
.byte %10000000