mirror of https://github.com/nmlgc/ReC98.git
[Reverse-engineering] [th03] Collision bitmap: Drawing vertical lines
Ironically only used for pellets, which are now confirmed to have a 2×2 (screen) / 2×1 (VRAM) hitbox. Might have been "decompilable", but it's sandwiched between undecompilable functions. Part of P0182, funded by Lmocinemod and [Anonymous].
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nmlgc
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c04ca8da91
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07561f4824
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@ -10,6 +10,7 @@ include th03/main/collmap.inc
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extrn _collmap_topleft:Point
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extrn _collmap_stripe_tile_w:word
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extrn _collmap_tile_h:word
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extrn _collmap_bottomright:Point
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extrn _collmap_pid:byte
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extrn _collmap:byte:(PLAYER_COUNT * COLLMAP_SIZE)
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@ -31,6 +32,65 @@ MAIN_04 group COLLMAP_TEXT
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.code
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assume cs:MAIN_04
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public _collmap_set_vline
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_collmap_set_vline proc far
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@@pattern equ <ah>
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@@first_bit equ <cl>
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@@first_bit_wide equ <cx> ; Just remove this
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@@rows_from_bottom equ <dx> ; Ensures clipping at the bottom edge
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@@collmap_p equ <bx>
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mov ax, _collmap_topleft.x
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mov dx, _collmap_topleft.y
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; Clip
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or ax, ax
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js short @@ret
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cmp ax, (PLAYFIELD_W shl 4)
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jge short @@ret
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or dx, dx
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js short @@ret
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cmp dx, (PLAYFIELD_H shl 4)
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jge short @@ret
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xor @@collmap_p, @@collmap_p
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cmp _collmap_pid, 0
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jz short @@set_collmap_p
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mov @@collmap_p, COLLMAP_SIZE
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@@set_collmap_p:
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add @@collmap_p, offset _collmap
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sar ax, (SUBPIXEL_BITS + COLLMAP_TILE_W_BITS)
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sar dx, (SUBPIXEL_BITS + COLLMAP_TILE_H_BITS)
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mov @@first_bit_wide, ax ; first_bit = AX;
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sar ax, 3 ; AX /= 8; (bits per byte)
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and @@first_bit_wide, (8 - 1) ; first_bit &= (8 - 1);
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add @@collmap_p, dx ; collmap_p += (
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offset_x ax, al ; DX + (AX * COLLMAP_H)
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add @@collmap_p, ax ; );
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mov ax, COLLMAP_H
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sub ax, dx
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mov @@rows_from_bottom, ax
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mov @@pattern, 80h
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shr @@pattern, @@first_bit
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mov cx, _collmap_tile_h
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even
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@@row_loop:
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or [@@collmap_p], @@pattern
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inc @@collmap_p
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dec @@rows_from_bottom
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loopne @@row_loop
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@@ret:
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ret
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_collmap_set_vline endp
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even
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public _collmap_set_slope_striped
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_collmap_set_slope_striped proc c far
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uses si, di
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@ -41,6 +41,13 @@ extern unsigned char collmap_pid;
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extern uint8_t collmap[PLAYER_COUNT][COLLMAP_MEMORY_W][COLLMAP_H];
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// -------------------
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// Sets all bits on a straight 1-tile wide vertical line, clipped to the
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// height of the collision bitmap. Takes the following parameters:
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// • [collmap_topleft] (X and Y)
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// • [collmap_tile_h] (height of the line)
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// • [collmap_pid]
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void collmap_set_vline();
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// Sets all bits on every [COLLMAP_SLOPE_VSTRIPE_DISTANCE]th row of a
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// potentially sloped vertical line across one whole playfield.
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// Takes the following parameters:
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@ -17080,61 +17080,10 @@ loc_13B2C:
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locret_13B41:
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retf
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sub_13A6E endp
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; =============== S U B R O U T I N E =======================================
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sub_13B42 proc far
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mov ax, _collmap_topleft.x
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mov dx, _collmap_topleft.y
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or ax, ax
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js short locret_13B98
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cmp ax, (PLAYFIELD_W shl 4)
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jge short locret_13B98
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or dx, dx
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js short locret_13B98
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cmp dx, (PLAYFIELD_H shl 4)
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jge short locret_13B98
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xor bx, bx
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cmp _collmap_pid, 0
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jz short loc_13B68
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mov bx, COLLMAP_SIZE
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loc_13B68:
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add bx, offset _collmap
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sar ax, 5
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sar dx, 5
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mov cx, ax
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sar ax, 3
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and cx, 7
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add bx, dx
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mov ah, COLLMAP_H
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mul ah
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add bx, ax
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mov ax, COLLMAP_H
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sub ax, dx
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mov dx, ax
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mov ah, 80h
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shr ah, cl
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mov cx, _collmap_tile_h
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nop
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loc_13B92:
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or [bx], ah
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inc bx
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dec dx
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loopne loc_13B92
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locret_13B98:
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retf
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sub_13B42 endp
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; ---------------------------------------------------------------------------
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nop
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main_04_TEXT ends
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COLLMAP_TEXT segment byte public 'CODE' use16
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extern _collmap_set_vline:proc
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extern _collmap_set_slope_striped:proc
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COLLMAP_TEXT ends
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@ -24959,7 +24908,7 @@ loc_17BA9:
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mov _collmap_topleft.y, ax
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mov al, [si+10h]
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mov _collmap_pid, al
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call sub_13B42
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call _collmap_set_vline
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loc_17BCA:
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jmp loc_17A3D
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