Introduction
Background
Introduction
bgtiles.asm
bgtiled.asm
bgtilem.asm
putstile.asm
putdtile.asm
puthtile.asm
putvtile.asm
putmtile.asm
wallmeld.asm
Math
Objects
Palettes
Tiles
Utilities
Wall Meld Routine
The following file is a routine written for the expedition project which corrects the display of the wall tiles in the background or window. There are two files for this routine, the actual routine and it's accompanying data table.
You can download the files as well if you don't want to cut and paste the text.
To download the files using a PC, right-click a link and select the option "Save Target As" then save the file as you would any other file from windows.
Explanation
Source
;************************************************************* ; Procedure Name : wall_meld ; ; Author : Marc Gale (Xalthorn or Eldara) ; ; Description : Written for the Expedition project, this ; procedure scans the background (or window, ; as the base address is passed to it) for ; any wall tiles, and corrects the actual ; image used based on the surrounding tiles. ; ; On Entry : B = Tile number used for the wall topping ; C = First tile of the wall set ; HL = Base Map address ; ; During : All registers are used ; ; On Exit : Nothing intentional ;************************************************************* wall_meld ld a,0 ldh [$4F],a ; make sure we're playing with bank 0 ld d,0 ; initialise the y counter .yloop: ld e,0 ; initialise the x counter .xloop: ld a,0 ; initialise the flag byte push af ; preserve it push bc ; preserve bc ld a,[hl] ; grab the current tile cp a,b ; are we the filler tile? jr z,.continue ; if so, continue cp a,c ; are we higher than the low number? jr c,.nocheck ; if not, don't bother doing the checks ld a,c ; get the wall set number add a,12 ; add twelve to it ld c,a ; put it back ld a,[hl] ; grab the current tile again cp a,c ; are we still in the wall set? jr nc,.nocheck ; if not, don't bother doing the checks jr .continue .nocheck pop bc ; restore bc pop af ; restore af (don't fill the stack) jp .donedrawing ; next tile .continue pop bc ; restore bc .row1: ld a,d ; grab the y counter cp 0 ; is it 0, the top of the map? jr z,.row2 ; if so we can't do a row up ld a,l ; subtract 32 from hl to move sub a,32 ; up a row ld l,a ; . ld a,h ; . sbc a,0 ; . ld h,a ; . .row1left: ld a,e ; get the x counter cp 0 ; is it 0, the left of the map? jr z,.row1middle ; if so, we can't go left dec hl ; move left one tile ld a,[hl] ; grab the tile data push bc ; preserve bc .row1lefta: cp a,b ; is it the filler tile? jr nz,.row1leftb ; if not, try the walls ; found wall, set the bit pop bc ; restore bc pop af ; restore af (a is the flag byte) set 7,a ; set bit 7 (128) push af ; preserve af push bc ; preserve bc jr .row1leftdone ; done this position, move to next .row1leftb: cp a,c ; are we higher than the low number? jr c,.row1leftdone ; if not, we're done here ld a,c ; get the wall base number add a,12 ; add 12 ld c,a ; put it back ld a,[hl] ; grab the map data again cp a,c ; are we still in the wall set? jr nc,.row1leftdone; if not, we're done here ; found wall, set the bit pop bc ; restore bc pop af ; restore af set 7,a ; set bit 7 (128) push af ; preserve af push bc ; preserve bc .row1leftdone: pop bc ; restore bc inc hl ; move right one .row1middle: ld a,[hl] ; grab the map data push bc ; preserve bc .row1middlea: cp a,b ; is it the filler tile? jr nz,.row1middleb ; if not, try the walls ; found wall, set the bit pop bc ; restore bc pop af ; restore af set 0,a ; set bit 0 (1) push af ; preserve af push bc ; preserve bc jr .row1middledone ; we're done here, move to next .row1middleb: cp a,c ; are we higher than the low number? jr c,.row1middledone ; if not, we're done here ld a,c ; get the wall base number add a,12 ; add 12 ld c,a ; put it back ld a,[hl] ; get the map data cp a,c ; are we still in the wall set? jr nc,.row1middledone ; if not, we're done here ; found wall, set the bit pop bc ; restore bc pop af ; restore af set 0,a ; set bit 0 (1) push af ; preserve af push bc ; preserve bc .row1middledone: pop bc ; restore bc .row1right: ld a,e ; get the x counter cp 31 ; is it 31, right hand edge? jr z,.donerow1 ; if so, we can't go right inc hl ; move right one tile ld a,[hl] ; grab the tile data push bc ; preserve bc .row1righta: cp a,b ; is it the filler tile? jr nz,.row1rightb ; if not, try the walls ; found wall, set the bit pop bc ; restore bc pop af ; restore af set 1,a ; set bit 1 (2) push af ; preserve af push bc ; preserve bc jr .row1rightdone ; we're done here .row1rightb: cp a,c ; are we higher than the low number? jr c,.row1rightdone ; if not, we're done here ld a,c ; get the wall base number add a,12 ; add 12 ld c,a ; put it back ld a,[hl] ; grab the map data cp a,c ; are we still in the wall set? jr nc,.row1rightdone ; if not, we're done here ; found wall, set the bit pop bc ; restore bc pop af ; restore af set 1,a ; set bit 1 (2) push af ; preserve af push bc ; preserve bc .row1rightdone: pop bc ; restore bc dec hl ; move left one .donerow1: push de ; preserve de ld de,32 ; move down a row add hl,de ; pop de ; restore de .row2: .row2left: ld a,e ; get the x counter cp 0 ; is it 0, left hand edge? jr z,.row2middle ; if so, we can't go left dec hl ; move left one tile ld a,[hl] ; grab the tile data push bc ; preserve bc .row2lefta: cp a,b ; is it the filler tile? jr nz,.row2leftb ; if not, try the walls ; found wall, set the bit pop bc ; restore bc pop af ; restore af set 6,a ; set bit 6 (64) push af ; preserve af push bc ; preserve bc jr .row2leftdone ; we're done here .row2leftb: cp a,c ; are we higher than the low number? jr c,.row2leftdone ; if not, we're done here ld a,c ; get the wall base number add a,12 ; add 12 ld c,a ; put it back ld a,[hl] ; grab the map data cp a,c ; are we still in the wall set? jr nc,.row2leftdone ; if not, we're done here ; found wall, set the bit pop bc ; restore bc pop af ; restore af set 6,a ; set bit 6 (64) push af ; preserve af push bc ; preserve bc .row2leftdone: pop bc ; restore bc inc hl ; move right one .row2middle: ; nothing to do here, this is the square we're setting .row2right: ld a,e ; get the x counter cp 31 ; is it 31, right hand edge? jr z,.row3 ; if so, we can't go right inc hl ; move right one tile ld a,[hl] ; grab the tile data push bc ; preserve bc .row2righta: cp a,b ; is it the filler tile? jr nz,.row2rightb ; if not, try the walls ; found wall, set the bit pop bc ; restore bc pop af ; restore af set 2,a ; set bit 2 (4) push af ; preserve af push bc ; preserve bc jr .row2rightdone ; we're done here .row2rightb: cp a,c ; are we higher than the low number? jr c,.row2rightdone ; if not, we're done here ld a,c ; get the wall base number add a,12 ; add 12 to it ld c,a ; put it back ld a,[hl] ; grab the map data cp a,c ; are we still in the wall set? jr nc,.row2rightdone ; if not, we're done here ; found wall, set the bit pop bc ; restore bc pop af ; restore af set 2,a ; set bit 2 (4) push af ; preserve af push bc ; preserve bc .row2rightdone: pop bc ; restore bc dec hl ; move left one .row3: ld a,d ; get the y counter cp 31 ; is it 31, bottom edge? jr z,.donerows ; if so, we can't go down push de ; move down one row, ld de,32 ; preserving and restoring add hl,de ; de as they are used for pop de ; the addition .row3left: ld a,e ; get the x counter cp 0 ; is it 0, the left hand edge? jr z,.row3middle ; if so, we can't go left dec hl ; move left one tile ld a,[hl] ; grab the tile data push bc ; preserve bc .row3lefta: cp a,b ; is it the filler tile? jr nz,.row3leftb ; if not, try the walls ; found wall, set the bit pop bc ; restore bc pop af ; restore af set 5,a ; set bit 5 (32) push af ; preserve af push bc ; preserve bc jr .row3leftdone ; we're done here .row3leftb: cp a,c ; are we higher than the low number? jr c,.row3leftdone ; if not, we're done here ld a,c ; get the wall base number add a,12 ; add 12 to it ld c,a ; put it back ld a,[hl] ; grab the map data cp a,c ; are we still in the wall set? jr nc,.row3leftdone ; if not, we're done here ; found wall, set the bit pop bc ; restore bc pop af ; restore af set 5,a ; set bit 5 (32) push af ; preserve af push bc ; preserve bc .row3leftdone: pop bc ; restore bc inc hl ; move right one .row3middle: ld a,[hl] ; grab the tile data push bc ; preserve bc .row3middlea: cp a,b ; is it the filler tile? jr nz,.row3middleb ; if not, try the walls ; found wall, set the bit pop bc ; restore bc pop af ; restore af set 4,a ; set bit 4 (16) push af ; preserve af push bc ; preserve bc jr .row3middledone ; we're done here .row3middleb: cp a,c ; are we higher than the low number? jr c,.row3middledone ; if not, we're done here ld a,c ; get the wall base number add a,12 ; add 12 to it ld c,a ; put it back ld a,[hl] ; grab the map data cp a,c ; are we still in the wall set? jr nc,.row3middledone ; if not, we're done here ; found wall, set the bit pop bc ; restore bc pop af ; restore af set 4,a ; set bit 4 (16) push af ; preserve af push bc ; preserve bc .row3middledone: pop bc ; restore bc .row3right: ld a,e ; get the x counter cp 31 ; is it 31, the right hand edge? jr z,.donerow3 ; if so, we can't go right inc hl ; move right one tile ld a,[hl] ; grab the tile data push bc ; preserve bc .row3righta: cp a,b ; is it the filler tile? jr nz,.row3rightb ; if not, try the walls ; found wall, set the bit pop bc ; restore bc pop af ; restore af set 3,a ; set bit 3 (8) push af ; preserve af push bc ; preserve bc jr .row3rightdone ; we're done here .row3rightb: cp a,c ; are we higher than the low number? jr c,.row3rightdone ; if not, we're done here ld a,c ; get the wall base number add a,12 ; add 12 to it ld c,a ; put it back ld a,[hl] ; grab the map data cp a,c ; are we still in the wall set? jr nc,.row3rightdone ; it not, we're done here ; found wall, set the bit pop bc ; restore bc pop af ; restore af set 3,a ; set bit 3 (8) push af ; preserve af push bc ; preserve bc .row3rightdone: pop bc ; restore bc dec hl ; move left one .donerow3: ld a,l ; subtract 32 from hl, sub a,32 ; bringing it up one row ld l,a ; ld a,h ; sbc a,0 ; ld h,a ; .donerows: ; okay, now we should have a byte set with the correct bits, let's ; get it into a pop af ; restore af push hl ; preserve the map pointer ld hl,walltable ; get the address of the data table push de ; preserve the counters ld d,0 ; add a to hl ld e,a ; . add hl,de ; . pop de ; restore the counters ld a,[hl] ; grab the data from the table pop hl ; restore the map pointer cp 0 ; is the entry 0, nothing to set? jr z,.donedrawing ; if so, we're done here cp 13 ; is the entry the filler value jr nz,.drawwall ; if not, test the wall values .drawfiller: ld a,b ; put the filler number in a jr .dodraw ; go draw the tile .drawwall: add a,c ; add the wall reference to the base dec a ; value and subtract one .dodraw: ld [hl],a ; put the data on the map .donedrawing: inc hl ; move to the next tile inc e ; increase the x counter ld a,e ; get the x counter cp 32 ; have we done 32 tiles (one row) jp nz,.xloop ; if not, go back and do another inc d ; increase the y counter ld a,d ; get the y counter cp 32 ; have we done 32 rows? jp nz,.yloop ; if not, go back and do another ret ; we're done, return
;******************************** ; walltab.asm ; data file for wallmeld.asm ;******************************** DB 00,00,00,00,00,00,00,07,00,00 DB 00,00,00,00,00,07,00,00,00,00 DB 00,00,00,04,00,00,00,00,08,04 DB 08,04,00,00,00,00,00,07,00,07 DB 00,00,00,00,00,07,00,07,00,00 DB 00,00,00,00,00,04,00,00,00,00 DB 08,04,08,04,00,00,00,06,00,03 DB 00,03,00,06,00,06,00,03,00,03 DB 00,02,05,02,01,13,01,13,00,02 DB 05,02,01,13,01,13,00,00,00,00 DB 00,03,00,03,00,06,00,06,00,03 DB 00,03,05,02,05,02,01,13,01,13 DB 05,02,05,02,01,13,01,12,00,00 DB 00,00,00,00,00,07,00,00,00,00 DB 00,00,00,07,00,00,00,00,08,04 DB 08,04,00,00,00,00,08,04,08,04 DB 00,00,00,00,00,00,00,00,00,00 DB 00,00,00,00,00,07,00,00,00,00 DB 00,04,00,04,00,00,00,00,08,04 DB 08,04,00,06,00,06,00,03,00,03 DB 00,06,00,06,00,03,00,03,00,02 DB 00,02,01,13,01,13,00,02,05,02 DB 01,13,01,09,00,06,00,06,00,03 DB 00,03,00,06,00,06,00,03,00,03 DB 05,02,05,02,01,13,01,12,05,02 DB 05,02,01,11,01,13
