m8si
Active member
How to put a tile at a specific location on the screen?
Let's say I would like to put tile on screen location 3,1 (in tiles) how can I do that in code?
I found out I can somehow put a tile on screen at "position 2" with a code taken from ChangeTileAtCollision. At first line (LDY #$02, original code has LDY temp1)
However this code will crash the game. Maybe because the tile I'm colliding with is never set to walkable after I run this code and I get an infinite loop. I tried to make it walkable and added another line after these: ChangeTileAtCollision #$00,#$00 but after that the code below stopped working...
Also another question. How can I tell what tile is at a given location?
E.g. IF Tile at location 4,3 is TileNumber02 ---> Do something
Let's say I would like to put tile on screen location 3,1 (in tiles) how can I do that in code?
I found out I can somehow put a tile on screen at "position 2" with a code taken from ChangeTileAtCollision. At first line (LDY #$02, original code has LDY temp1)
However this code will crash the game. Maybe because the tile I'm colliding with is never set to walkable after I run this code and I get an infinite loop. I tried to make it walkable and added another line after these: ChangeTileAtCollision #$00,#$00 but after that the code below stopped working...
Also another question. How can I tell what tile is at a given location?
E.g. IF Tile at location 4,3 is TileNumber02 ---> Do something
Code:
LDY #$02 ;; X Position goes here this was originally LDY temp1
LDA temp2
BEQ +isEvenCt
;; is an odd ct, so looking in collisionTable2
LDA #$00 ; = collision to change into.
STA collisionTable2,y
JMP +doneWithTileUpdate
+isEvenCt
LDA #$00 ; = collision to change into.
STA collisionTable,y
+doneWithTileUpdate
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;;; This part will actually update the tile with tile 0 in the tile set.
;;; ys is carried over from above.
;;; GET THE HIGH BYTE OF THE TILE TO CHANGE
LDA temp2
BEQ +isEvenNt
;; is odd nt
LDA #$24
JMP +gotNt
+isEvenNt
;; is even nt
LDA #$20
+gotNt
STA temp1
;;; GET THE LOW BYTE OF THE TILE TO CHANGE
TYA
STA temp
LSR
LSR
LSR
LSR
LSR
LSR
clc
ADC temp1
STA temp2 ;;;temp16+1
TYA
AND #%11110000
ASL
ASL
STA tempz
TYA
AND #%00001111
ASL
ORA tempz
STA temp3 ;temp16
;;; SET THE TILE NUMBER TO CHANGE TO.
LDA #$20 ;; the tile to change.
;;; this is in tiles, so if you wanted the second "metatile",
;;; use 2, not 1. If you wanted the tile in the next row,
;;; use #$20, not #$10. Etc.
STA tempA
CLC
ADC #$01
STA tempB
CLC
ADC #$0F
STA tempC
CLC
ADC #$01
STA tempD
LDY #$00
LDA temp2
STA scrollUpdateRam,y
INY
LDA temp3
STA scrollUpdateRam,y
INY
LDA tempA
STA scrollUpdateRam,y
INY
LDA temp2
STA scrollUpdateRam,y
INY
LDA temp3
CLC
ADC #$01
STA scrollUpdateRam,y
INY
LDA tempB
STA scrollUpdateRam,y
INY
LDA temp3
CLC
ADC #$20
STA temp3
LDA temp2
ADC #$00
STA temp2
LDA temp2
STA scrollUpdateRam,y
INY
LDA temp3
STA scrollUpdateRam,y
INY
LDA tempC
STA scrollUpdateRam,y
INY
LDA temp2
STA scrollUpdateRam,y
INY
LDA temp3
CLC
ADC #$01
STA scrollUpdateRam,y
INY
LDA tempD
STA scrollUpdateRam,y
INY
TYA
STA maxScrollOffsetCounter
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;; Turn on update screen on next frame.
LDA updateScreenData
ORA #%0000100
STA updateScreenData
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
Last edited:
