mirror of
https://github.com/sehugg/8bitworkshop.git
synced 2024-11-25 18:33:11 +00:00
206 lines
3.7 KiB
Plaintext
206 lines
3.7 KiB
Plaintext
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MAX_MSPRITES = 28
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MIN_Y_SPACING = 35
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DEBUG = 1
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.code
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.global _msprite_render_init
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_msprite_render_init:
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lda #0
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sta j
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sta k
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sta $d001 ; ypos #0
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sta $d003
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sta $d005
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sta $d007
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sta $d009
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sta $d00b
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sta $d00d
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sta $d00f ; ypos #7
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lda #$ff
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sta $d015 ; sprite enable
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rts
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.global _msprite_render_section
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_msprite_render_section:
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lda $d012
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clc
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adc #MIN_Y_SPACING
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sta bailout_line
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@loop:
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.ifdef DEBUG
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inc $d020
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.endif
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lda $d012
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cmp bailout_line
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bcs @loopexit
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ldy k
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cpy #MAX_MSPRITES
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bcs @loopexit
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lda _msprite_order,y ; $ff = end of sprite list
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tay ; Y = sprite index from sort array
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lda j
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asl
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tax ; X = j * 2
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; if (VIC.spr_pos[j].y >= 250) break;
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lda $d001,x
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cmp #250
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bcs @loopexit ; offscreen?
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; if (VIC.spr_pos[j].y+22 >= VIC.rasterline) break;
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clc
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adc #22
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cmp $d012 ; are we done drawing
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bcs @loopexit ; this sprite yet?
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; VIC.spr_pos[j].y = msprite_y[i];
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lda _msprite_y,y
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sta $d001,x
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; VIC.spr_pos[j].x = msprite_x[i];
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lda _msprite_x_lo,y
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sta $d000,x
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ldx j ; X = j
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; VIC.spr_color[j] = msprite_color[i];
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lda _msprite_color,y
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sta $d027,x
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; POKE(0x7f8+j, msprite_shape[i]);
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lda _msprite_shape,y
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sta $07f8,x
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; set hi X bit
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lda _msprite_x_hi,y
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lsr
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lda NOTBITS,x
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and $d010
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bcc @nohix
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ora BITS,x
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@nohix:
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sta $d010 ; update X hi bits
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inc k ; next object
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inx
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txa
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and #7
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sta j ; next h/w sprite
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jmp @loop
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@loopexit:
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.ifdef DEBUG
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lda #0
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sta $d020
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.endif
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rts
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; http://selmiak.bplaced.net/games/c64/index.php?lang=eng&game=Tutorials&page=Sprite-Multiplexing
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.global _msprite_sort
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_msprite_sort:
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ldx #$00
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@sortloop:
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ldy _msprite_order+1,x
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lda _msprite_y,y
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ldy _msprite_order,x
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cmp _msprite_y,y
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bcs @sortskip
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stx @sortreload+1
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@sortswap:
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lda _msprite_order+1,x
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sta _msprite_order,x
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tya
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sta _msprite_order+1,x
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cpx #$00
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beq @sortreload
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dex
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ldy _msprite_order+1,x
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lda _msprite_y,y
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ldy _msprite_order,x
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cmp _msprite_y,y
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bcc @sortswap
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@sortreload:
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ldx #$00 ; self-modifying code
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@sortskip:
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inx
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cpx #MAX_MSPRITES-1
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bcc @sortloop
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rts
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.global _msprite_add_velocity
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_msprite_add_velocity:
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tay
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dey
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@loop:
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lda _msprite_y_frac,y
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clc
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adc _msprite_yvel_lo,y
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sta _msprite_y_frac,y
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lda _msprite_y,y
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adc _msprite_yvel_hi,y
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sta _msprite_y,y
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lda _msprite_x_frac,y
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clc
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adc _msprite_xvel_lo,y
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sta _msprite_x_frac,y
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lda _msprite_xvel_hi,y
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bmi @xneg
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lda _msprite_x_lo,y
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adc _msprite_xvel_hi,y
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sta _msprite_x_lo,y
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lda _msprite_x_hi,y
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adc #0
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sta _msprite_x_hi,y
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dey
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bpl @loop
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rts
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@xneg:
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lda _msprite_x_lo,y
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adc _msprite_xvel_hi,y
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sta _msprite_x_lo,y
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lda _msprite_x_hi,y
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adc #$ff
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sta _msprite_x_hi,y
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dey
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bpl @loop
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rts
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BITS:
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.byte $01,$02,$04,$08,$10,$20,$40,$80
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NOTBITS:
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.byte $FE,$FD,$FB,$F7,$EF,$DF,$BF,$7F
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;;;;;
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.data
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j: .res 1 ; h/w sprite index
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k: .res 1 ; object index
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bailout_line: .res 1
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.global _msprite_order
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.global _msprite_x_lo
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.global _msprite_x_hi
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.global _msprite_y
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.global _msprite_color
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.global _msprite_shape
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.global _msprite_flags
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.global _msprite_last_y
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_msprite_order: .res MAX_MSPRITES
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_msprite_x_lo: .res MAX_MSPRITES
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_msprite_x_hi: .res MAX_MSPRITES
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_msprite_y: .res MAX_MSPRITES
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_msprite_color: .res MAX_MSPRITES
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_msprite_shape: .res MAX_MSPRITES
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_msprite_flags: .res MAX_MSPRITES
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_msprite_last_y:.res 1
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.global _msprite_x_frac
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.global _msprite_xvel_lo
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.global _msprite_xvel_hi
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.global _msprite_y_frac
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.global _msprite_yvel_lo
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.global _msprite_yvel_hi
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_msprite_x_frac: .res MAX_MSPRITES
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_msprite_xvel_lo: .res MAX_MSPRITES
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_msprite_xvel_hi: .res MAX_MSPRITES
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_msprite_y_frac: .res MAX_MSPRITES
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_msprite_yvel_lo: .res MAX_MSPRITES
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_msprite_yvel_hi: .res MAX_MSPRITES
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