[Reverse-engineering] [th03] Collision bitmap: Drawing slopes (undecompilable)

Reason: Self-modifying. -.- Only used in Chiyuri's EX Attack (the one with the diagonal lasers). Part of P0182, funded by Lmocinemod and [Anonymous].
2022-02-06 17:24:09 +01:00 · 2022-02-06 17:24:09 +01:00 · c04ca8da91
parent 3072208336
commit c04ca8da91
8 changed files with 146 additions and 76 deletions
--- a/Makefile.mak
+++ b/Makefile.mak
@ -98,7 +98,7 @@ bin\th03\op.exe: th03\op_01.cpp th03\op_02.cpp bin\th03\scoredat.obj th03\op_03.
 $**
 |

-bin\th03\main.exe: bin\th03\main.obj th03\main_01.cpp bin\th03\cfg_lres.obj bin\th01\vplanset.obj bin\th02\snd_mode.obj bin\th02\snd_pmdr.obj bin\th03\vector2.obj bin\th03\exit.obj bin\th03\vector1.obj bin\th02\frmdely1.obj bin\th03\input_s.obj bin\th02\snd_se_r.obj bin\th03\snd_se.obj bin\th03\snd_kaja.obj bin\th03\initmain.obj bin\th03\pi_load.obj bin\th03\inp_m_w.obj bin\th03\hfliplut.obj th03\mrs.cpp th03\sprite16.cpp
+bin\th03\main.exe: bin\th03\main.obj th03\main_01.cpp bin\th03\cfg_lres.obj bin\th01\vplanset.obj bin\th02\snd_mode.obj bin\th02\snd_pmdr.obj bin\th03\vector2.obj bin\th03\exit.obj bin\th03\vector1.obj bin\th02\frmdely1.obj bin\th03\input_s.obj bin\th02\snd_se_r.obj bin\th03\snd_se.obj bin\th03\snd_kaja.obj bin\th03\initmain.obj bin\th03\pi_load.obj bin\th03\inp_m_w.obj bin\th03\collmap.obj bin\th03\hfliplut.obj th03\mrs.cpp th03\sprite16.cpp
 	$(CC) $(CFLAGS) $(LARGE_LFLAGS) -Z -DGAME=3 -nbin\th03\ -eMAIN.EXE @&&|
 $**
 |
--- a/1
+++ b/1
@ -80,6 +80,7 @@ BMP2ARR = bin\\Pipeline\\bmp2arr.exe
 : th03\\cdg_put.asm |> !as3 |>
 : th03\\cdg_p_na.asm |> !as3 |>
 : th03\\hfliplut.asm |> !as3 |>
+: th03\\collmap.asm |> !as3 |>
 : th03_op.asm |> !as |> bin\\th03\\op.obj
 : th03_main.asm | \
 	th03/sprites/score.asp \
--- a/Tupfile.bat
+++ b/Tupfile.bat
@ -32,6 +32,7 @@ tasm32 /m /mx /kh32768 /t th02_maine.asm bin\th02\maine.obj
 tasm32 /m /mx /kh32768 /t /DTHIEF libs\sprite16\sprite16.asm bin\th03\zunsp.obj
 tasm32 /m /mx /kh32768 /t /dGAME=3 th03\cdg_put.asm bin\th03\cdg_put.obj
 tasm32 /m /mx /kh32768 /t /dGAME=3 th03\cdg_p_na.asm bin\th03\cdg_p_na.obj
+tasm32 /m /mx /kh32768 /t /dGAME=3 th03\\collmap.asm bin\th03\collmap.obj
 tasm32 /m /mx /kh32768 /t /dGAME=3 th03\\hfliplut.asm bin\th03\hfliplut.obj
 tasm32 /m /mx /kh32768 /t th03_op.asm bin\th03\op.obj
 tasm32 /m /mx /kh32768 /t th03_main.asm bin\th03\main.obj
--- a/th03/collmap.asm
+++ b/th03/collmap.asm
@ -0,0 +1 @@
+include th03/main/collmap.asm
--- a/th03/main/collmap.asm
+++ b/th03/main/collmap.asm
@ -0,0 +1,120 @@
+	.186
+	.model use16 large
+	locals
+
+include libs/master.lib/macros.inc
+include th01/math/subpixel.inc
+include th03/common.inc
+include th03/main/playfld.inc
+include th03/main/collmap.inc
+
+extrn _collmap_topleft:Point
+extrn _collmap_stripe_tile_w:word
+extrn _collmap_bottomright:Point
+extrn _collmap_pid:byte
+extrn _collmap:byte:(PLAYER_COUNT * COLLMAP_SIZE)
+
+; Sets @@dst to the offset of column @@x inside [collmap].
+offset_x macro @@dst:req, @@x:req
+	if ((@@dst eq ax) and (@@x eq al))
+		; MODDERS: This performs a 8→16-bit multiplication of AX = (AH * AL).
+		; Effectively limits both COLLMAP_H and COLLMAP_MEMORY_W to 8 bits!
+		mov	ah, COLLMAP_H
+		mul	ah
+	else
+		.err "Come on, just rewrite this in C++."
+	endif
+endm
+
+MAIN_04 group COLLMAP_TEXT
+
+	.code
+	assume cs:MAIN_04
+
+public _collmap_set_slope_striped
+_collmap_set_slope_striped proc c far
+	uses si, di
+	@@collmap_p     	equ <bx>
+	@@first_bit     	equ <cl>
+	@@first_bit_wide	equ <cx>	; Just remove this
+	@@left          	equ <si>
+	@@y_double      	equ <di>
+
+SLOPE_STRIPES = (COLLMAP_H / COLLMAP_SLOPE_VSTRIPE_DISTANCE)
+
+	mov	bx, (COLLMAP_H - 1)
+	cmp	_collmap_pid, 0
+	jz	short @@set_collmap_base
+	add	bx, COLLMAP_SIZE
+
+@@set_collmap_base:
+	add	bx, offset _collmap
+	mov	@@collmap_p_base_player_and_row, bx
+
+	; @@pattern = ~(0xFF >> collmap_sprite_tile_w);
+	; AH needs to be 0x00 for the carry pixel rotate trick below.
+	mov	al, 11111111b
+	mov	cx, _collmap_stripe_tile_w
+	shr	al, cl
+	not	al
+	xor	ah, ah
+	mov	@@pattern, ax
+
+	mov	ax, _collmap_bottomright.x
+	sub	ax, _collmap_topleft.x
+	mov	@@slope_subpixel_w, ax
+	jmp	short $+2
+	mov	@@left, _collmap_bottomright.x
+	mov	@@y_double, (SLOPE_STRIPES - 1)
+	even
+
+@@row_loop:
+	mov     	ax, @@left
+	shr     	ax, (SUBPIXEL_BITS + COLLMAP_TILE_W_BITS)
+	mov     	@@first_bit_wide, ax
+	and     	@@first_bit_wide, 7
+	shr     	ax, 3 	; AX = ((AX / BYTE_DOTS) * COLLMAP_H)
+	offset_x	ax, al	;
+
+	@@collmap_p_base_player_and_row = word ptr $+1
+	mov	@@collmap_p, 1234h
+	add	@@collmap_p, ax
+
+	; Right-rotate the pattern by [first_bit]. If the pattern then extends into
+	; a second bitmap byte, that byte's pattern will end up in AH.
+	@@pattern = word ptr $+1
+	mov	ax, 1234h
+	ror	ax, @@first_bit
+	or	[@@collmap_p], al
+	or	ah, ah
+	jz	short @@skip_blank
+	add	@@collmap_p, COLLMAP_H
+	or	[@@collmap_p], ah
+
+@@skip_blank:
+	dec	@@y_double
+	jz	short @@ret
+
+	; Interpolate new left X coordinate
+	;
+	; left = (collmap_topleft.x + (
+	; 	static_cast<long>(slope_subpixel_w * y_double) / SLOPE_STRIPES
+	; ));
+	@@slope_subpixel_w = word ptr $+1
+	mov	ax, 1234h
+	imul	@@y_double
+	mov	cx, SLOPE_STRIPES
+	idiv	cx	; 32-bit division of DX:AX by CX!
+	mov	@@left, _collmap_topleft.x
+	add	@@left, ax
+
+	sub	@@collmap_p_base_player_and_row, COLLMAP_SLOPE_VSTRIPE_DISTANCE
+	jmp	short @@row_loop
+; ---------------------------------------------------------------------------
+
+@@ret:
+	ret
+_collmap_set_slope_striped endp
+	even
+
+	end
--- a/th03/main/collmap.hpp
+++ b/th03/main/collmap.hpp
@ -19,6 +19,8 @@ static const char COLLMAP_TILE_H_BITS = 1;
 static const size_t COLLMAP_MEMORY_W = ((PLAYFIELD_W / COLLMAP_TILE_W) / 8);
 static const size_t COLLMAP_H = (PLAYFIELD_H / COLLMAP_TILE_H);
 static const size_t COLLMAP_SIZE = (COLLMAP_MEMORY_W * COLLMAP_H);
+
+static const collmap_tile_amount_t COLLMAP_SLOPE_VSTRIPE_DISTANCE = 2;
 // ---------

 // Function parameters
@ -38,4 +40,13 @@ extern unsigned char collmap_pid;
 // Stored as columns from left to right, not rows from top to bottom.
 extern uint8_t collmap[PLAYER_COUNT][COLLMAP_MEMORY_W][COLLMAP_H];
 // -------------------
+
+// Sets all bits on every [COLLMAP_SLOPE_VSTRIPE_DISTANCE]th row of a
+// potentially sloped vertical line across one whole playfield.
+// Takes the following parameters:
+// • [collmap_topleft.x] (always uses 0 for [y])
+// • [collmap_bottomright.x] (always uses to_sp(PLAYFIELD_H) for [y])
+// • [collmap_stripe_tile_w] (between 0 and 7)
+// • [collmap_pid]
+void collmap_set_slope_striped();
 /// ----------------
--- a/th03/main/collmap.inc
+++ b/th03/main/collmap.inc
@ -6,3 +6,5 @@ COLLMAP_TILE_H_BITS = 1
 COLLMAP_MEMORY_W = ((PLAYFIELD_W / COLLMAP_TILE_W) / 8)
 COLLMAP_H = (PLAYFIELD_H / COLLMAP_TILE_H)
 COLLMAP_SIZE = COLLMAP_MEMORY_W * COLLMAP_H
+
+COLLMAP_SLOPE_VSTRIPE_DISTANCE = 2
--- a/th03_main.asm
+++ b/th03_main.asm
@ -28,6 +28,7 @@ include libs/sprite16/sprite16.inc
 	extern _execl:proc

 main_01 group main_0_TEXT, CFG_LRES_TEXT, main_01_TEXT
+main_04 group main_04_TEXT, COLLMAP_TEXT, main_04__TEXT

 ; ===========================================================================

@ -16963,7 +16964,7 @@ main_03_TEXT	ends

 ; Segment type:	Pure code
 main_04_TEXT	segment	byte public 'CODE' use16
-		assume cs:main_04_TEXT
+		assume cs:main_04
 		;org 0Ah
 		assume es:nothing, ss:nothing, ds:_DATA, fs:nothing, gs:nothing

@ -17131,80 +17132,13 @@ sub_13B42	endp

 ; ---------------------------------------------------------------------------
 		nop
+main_04_TEXT	ends

-; =============== S U B	R O U T	I N E =======================================
+COLLMAP_TEXT	segment byte public 'CODE' use16
+	extern _collmap_set_slope_striped:proc
+COLLMAP_TEXT	ends

-
-sub_13B9A	proc far
-		push	si
-		push	di
-		mov	bx, (COLLMAP_H - 1)
-		cmp	_collmap_pid, 0
-		jz	short loc_13BAA
-		add	bx, COLLMAP_SIZE
-
-loc_13BAA:
-		add	bx, offset _collmap
-		mov	word ptr cs:loc_13BE9+1, bx
-		mov	al, 11111111b
-		mov	cx, _collmap_stripe_tile_w
-		shr	al, cl
-		not	al
-		xor	ah, ah
-		mov	word ptr cs:loc_13BEE+1, ax
-		mov	ax, _collmap_bottomright.x
-		sub	ax, _collmap_topleft.x
-		mov	word ptr cs:loc_13C02+1, ax
-		jmp	short $+2
-		mov	si, _collmap_bottomright.x
-		mov	di, 5Bh	; '['
-		nop
-
-loc_13BD8:
-		mov	ax, si
-		shr	ax, 5
-		mov	cx, ax
-		and	cx, 7
-		shr	ax, 3
-		mov	ah, COLLMAP_H
-		mul	ah
-
-loc_13BE9:
-		mov	bx, 1234h
-		add	bx, ax
-
-loc_13BEE:
-		mov	ax, 1234h
-		ror	ax, cl
-		or	[bx], al
-		or	ah, ah
-		jz	short loc_13BFF
-		add	bx, COLLMAP_H
-		or	[bx], ah
-
-loc_13BFF:
-		dec	di
-		jz	short loc_13C1A
-
-loc_13C02:
-		mov	ax, 1234h
-		imul	di
-		mov	cx, 5Ch
-		idiv	cx
-		mov	si, _collmap_topleft.x
-		add	si, ax
-		sub	word ptr cs:loc_13BE9+1, 2
-		jmp	short loc_13BD8
-; ---------------------------------------------------------------------------
-
-loc_13C1A:
-		pop	di
-		pop	si
-		retf
-sub_13B9A	endp
-
-; ---------------------------------------------------------------------------
-		nop
+main_04__TEXT	segment	byte public 'CODE' use16

 ; =============== S U B	R O U T	I N E =======================================

@ -25980,7 +25914,7 @@ loc_183B9:
 		retf
 sub_1837C	endp

-main_04_TEXT	ends
+main_04__TEXT	ends

 ; ===========================================================================

@ -27625,7 +27559,7 @@ loc_192DB:
 		add	si, 20h	; ' '
 		mov	ax, [si+2]
 		mov	_collmap_bottomright.x, ax
-		call	sub_13B9A
+		call	_collmap_set_slope_striped
 		jmp	short loc_1930C
 ; ---------------------------------------------------------------------------