Software maze wall detection

[+Karl G]

Does anyone have any good sample code for software playfield collision detection? I'm still trying to debug mine, and I'm wondering if there's a better way than what I am doing. Here's what I have so far to convert object screen coordinates for a 2-line kernel to a 40 wide by 22 tall playfield (symmetric, mirrored):

 

; X Value in A, Y value in Y. Zero set if no playfield block.
PFWall
    sty Temp2
    lsr
    lsr
    cmp #20
    bcc ____skip_adjust_x_pixel
    sta Temp1
    lda #39
    sec
    sbc Temp1
____skip_adjust_x_pixel
    sta Temp1
    cmp #4
    bcs ____skip_pf0
    ldy #0
    jmp ____done_pfx
____skip_pf0

    cmp #12
    bcs ____skip_pf1
    ldy #2
    jmp ____done_pfx
____skip_pf1

    ldy #4
____done_pfx

    lda PF0Ptr,y
    sta TempPtr
    lda PF0Ptr+1,y
    sta TempPtr+1

    lda Temp2
    lsr
    lsr
    tay
    lda (TempPtr),y
    ldy Temp1
    and pfpixel_mask,y
    rts
; End PFWall

pfpixel_mask
    .byte bit4, bit5, bit6, bit7
    .byte bit7, bit6, bit5, bit4, bit3, bit2, bit1, bit0
    .byte bit0, bit1, bit2, bit3, bit4, bit5, bit6, bit7

DataPF0:
	.byte $F0,$10,$10,$90,$90,$90,$90,$00
	.byte $00,$90,$10,$10,$90,$00,$00,$90
	.byte $10,$10,$F0,$10,$10,$F0
DataPF1:
	.byte $E7,$00,$00,$E4,$04,$04,$E4,$07
	.byte $04,$E4,$00,$00,$FC,$04,$04,$FC
	.byte $04,$04,$E4,$00,$00,$E7
DataPF2:
	.byte $FF,$09,$09,$C1,$41,$08,$08,$7F
	.byte $00,$00,$4F,$48,$C8,$09,$09,$49
	.byte $01,$01,$4F,$00,$00,$FF

Any samples or tips would be appreciated!

[+splendidnut]

Looks about right to me.  You could swap out some of the branch logic and have a lookup table for which PF byte to use (y value used in the LDA PF0Ptr,y instructions).  That would save cycle time and take about the same amount of space.

[Omegamatrix]

I took a stab at it. Might not be exactly what you are looking for but could give you some ideas.

 

SoftwarePfCollision.zip

 

 

[+Karl G]

5 hours ago, Omegamatrix said:

I took a stab at it. Might not be exactly what you are looking for but could give you some ideas.

 

SoftwarePfCollision.zip 8.28 kB · 4 downloads

 

 

 

Thank you! This is indeed useful.