[Reverse-engineering] [th04/th05] ZUN Soft logo explosions

Which seemed a nicer and more debuggable intro to how ZUN implements
sprites than starting with a random structure from MAIN.EXE.

Funded by -Tom-.

th04/zunsoft.asm

@@ -0,0 +1,237 @@
+; Spawns [n] new explosions at [origin].
+; [origin] uses screen pixels, *not* the 1/16th-pixel units of the structure.
+
+; void pascal zunsoft_pyro_new(Point origin, int n, char patnum_base)
+_zunsoft_pyro_new	proc pascal near
+	local @@pyros_created:word, @@i:word
+	arg @@origin:Point, @@n:word, @@patnum_base:byte
+
+	push	si
+	push	di
+	mov	di, @@origin.y
+	mov	@@pyros_created, 0
+	mov	ax, 16
+	imul	@@origin.x
+	mov	@@origin.x, ax
+	mov	ax, 16
+	imul	di
+	mov	di, ax
+	mov	si, offset _zunsoft_pyros
+	mov	@@i, 0
+	jmp	short loc_B68D
+
+loc_B63E:
+	cmp	[si+zunsoft_pyro_t.alive], 0
+	jnz	short loc_B687
+	mov	[si+zunsoft_pyro_t.alive], 1
+	mov	[si+zunsoft_pyro_t.frame], 0
+	mov	[si+zunsoft_pyro_t.origin.x], di
+	mov	ax, @@origin.x
+	mov	[si+zunsoft_pyro_t.origin.y], ax
+	mov	[si+zunsoft_pyro_t.distance], 0
+	mov	[si+zunsoft_pyro_t.distance_prev], 0
+	call	IRand
+	mov	bx, 224
+	cwd
+	idiv	bx
+	add	dx, 64
+	mov	[si+zunsoft_pyro_t.speed], dx
+	call	IRand
+	mov	[si+zunsoft_pyro_t.angle], al
+	mov	al, @@patnum_base
+	mov	[si+zunsoft_pyro_t.patnum_base], al
+	inc	@@pyros_created
+	mov	ax, @@pyros_created
+	cmp	ax, @@n
+	jge	short loc_B694
+
+loc_B687:
+	inc	@@i
+	add	si, size zunsoft_pyro_t
+
+loc_B68D:
+	cmp	@@i, ZUNSOFT_PYRO_COUNT
+	jl	short loc_B63E
+
+loc_B694:
+	pop	di
+	pop	si
+	ret
+_zunsoft_pyro_new	endp
+
+
+; void pascal zunsoft_update_and_render(void)
+_zunsoft_update_and_render	proc pascal near
+	local @@patnum:word, @@draw_y:word, @@draw_x:word, @@anim_sprite:word
+
+	push	si
+	push	di
+	mov	si, offset _zunsoft_pyros
+	xor	di, di
+	jmp	loc_B7B9
+
+loc_B6A8:
+	cmp	[si+zunsoft_pyro_t.alive], 1
+	jnz	loc_B7B5
+	inc	[si+zunsoft_pyro_t.frame]
+	mov	al, [si+zunsoft_pyro_t.frame]
+	mov	ah, 0
+	mov	bx, 4
+	cwd
+	idiv	bx
+	mov	@@anim_sprite, ax
+	mov	al, [si+zunsoft_pyro_t.patnum_base]
+	mov	ah, 0
+	add	ax, @@anim_sprite
+	mov	@@patnum, ax
+	cmp	[si+zunsoft_pyro_t.frame], 40
+	jb	short loc_B6DB
+	mov	[si+zunsoft_pyro_t.alive], 0
+	mov	[si+zunsoft_pyro_t.frame], 0
+	jmp	loc_B7B5
+
+loc_B6DB:
+	cmp	[si+zunsoft_pyro_t.frame], 16
+	jnb	short loc_B6FA
+	mov	ax, [si+zunsoft_pyro_t.origin.x]
+	mov	bx, 16
+	cwd
+	idiv	bx
+	add	ax, -8
+	push	ax
+	mov	ax, [si+zunsoft_pyro_t.origin.y]
+	cwd
+	idiv	bx
+	add	ax, -8
+	jmp	loc_B7AC
+
+loc_B6FA:
+	cmp	[si+zunsoft_pyro_t.frame], 32
+	jnb	short loc_B754
+	cmp	[si+zunsoft_pyro_t.frame], 16
+	jnz	short loc_B70D
+	call	snd_se_play pascal, 15
+
+loc_B70D:
+	mov	ax, [si+zunsoft_pyro_t.distance]
+	mov	[si+zunsoft_pyro_t.distance_prev], ax
+	mov	ax, [si+zunsoft_pyro_t.speed]
+	add	[si+zunsoft_pyro_t.distance], ax
+	push	[si+zunsoft_pyro_t.origin.x]
+	push	[si+zunsoft_pyro_t.distance]
+	mov	al, [si+zunsoft_pyro_t.angle]
+	mov	ah, 0
+	add	ax, ax
+	mov	bx, ax
+	push	_CosTable8[bx]
+	call	vector1_at
+	add	ax, -128
+	mov	@@draw_x, ax
+	push	[si+zunsoft_pyro_t.origin.y]
+	push	[si+zunsoft_pyro_t.distance]
+	mov	al, [si+zunsoft_pyro_t.angle]
+	mov	ah, 0
+	add	ax, ax
+	mov	bx, ax
+	push	_SinTable8[bx]
+	call	vector1_at
+	add	ax, -128
+	jmp	short loc_B799
+
+loc_B754:
+	mov	ax, [si+zunsoft_pyro_t.distance]
+	mov	[si+zunsoft_pyro_t.distance_prev], ax
+	mov	ax, [si+zunsoft_pyro_t.speed]
+	add	[si+zunsoft_pyro_t.distance], ax
+	push	[si+zunsoft_pyro_t.origin.x]
+	push	[si+zunsoft_pyro_t.distance]
+	mov	al, [si+zunsoft_pyro_t.angle]
+	mov	ah, 0
+	add	ax, ax
+	mov	bx, ax
+	push	_CosTable8[bx]
+	call	vector1_at
+	add	ax, -256
+	mov	@@draw_x, ax
+	push	[si+zunsoft_pyro_t.origin.y]
+	push	[si+zunsoft_pyro_t.distance]
+	mov	al, [si+zunsoft_pyro_t.angle]
+	mov	ah, 0
+	add	ax, ax
+	mov	bx, ax
+	push	_SinTable8[bx]
+	call	vector1_at
+	add	ax, -256
+
+loc_B799:
+	mov	@@draw_y, ax
+	mov	ax, @@draw_x
+	mov	bx, 16
+	cwd
+	idiv	bx
+	push	ax
+	mov	ax, @@draw_y
+	cwd
+	idiv	bx
+
+loc_B7AC:
+	push	ax
+	push	@@patnum
+	call	super_put_rect
+
+loc_B7B5:
+	inc	di
+	add	si, size zunsoft_pyro_t
+
+loc_B7B9:
+	cmp	di, ZUNSOFT_PYRO_COUNT
+	jl	loc_B6A8
+	pop	di
+	pop	si
+	ret
+_zunsoft_update_and_render	endp
+
+
+; void pascal zunsoft_palette_update_and_show(int tone)
+_zunsoft_palette_update_and_show	proc near
+	arg @@tone:word
+
+	push	bp
+	mov	bp, sp
+	push	si
+	push	di
+	xor	si, si
+	jmp	short loc_B7F6
+
+loc_B7CE:
+	xor	di, di
+	jmp	short loc_B7F0
+
+loc_B7D2:
+	mov	bx, si
+	imul	bx, 3
+	mov	al, _zunsoft_palette[bx+di]
+	mov	ah, 0
+	imul	@@tone
+	mov	bx, 100
+	cwd
+	idiv	bx
+	mov	bx, si
+	imul	bx, 3
+	mov	Palettes[bx+di], al
+	inc	di
+
+loc_B7F0:
+	cmp	di, 3
+	jl	short loc_B7D2
+	inc	si
+
+loc_B7F6:
+	cmp	si, 15
+	jl	short loc_B7CE
+	call	palette_show
+	pop	di
+	pop	si
+	pop	bp
+	retn	2
+_zunsoft_palette_update_and_show	endp

th04/zunsoft[bss].asm

@@ -0,0 +1,23 @@
+; Copy of the palette used during the logo, to allow non-blocking fades in
+; contrast to master.lib's blocking palette_black_in() and palette_black_out()
+; functions. (Then again, master.lib has the PaletteTone global for that...)
+_zunsoft_palette	db 48 dup(?)
+
+; ZUN Soft logo explosion structure.
+; These are only animated by increasing the distance; origin, angle, and speed
+; stay constant.
+; For increased precision, all coordinates (origin, distance, and speed) are
+; stored in units of 1/16th of a pixel.
+zunsoft_pyro_t struc
+	alive	db ?
+	frame	db ? ; since creation
+	origin	Point ?
+	distance_prev	dw ? ; unused
+	distance	dw ?
+	speed	dw ?
+	angle	db ?
+	patnum_base	db ? ; displayed sprite is incremented every 4 frames
+zunsoft_pyro_t ends
+
+ZUNSOFT_PYRO_COUNT = 256
+_zunsoft_pyros	zunsoft_pyro_t ZUNSOFT_PYRO_COUNT dup(<?>)