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