A92: Using a 2 dimensional array to put sprites
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A92: Using a 2 dimensional array to put sprites
How can l sort of use "indirection" to put a sprite at a location? Realize
that part of the code would not work because l had to make it up, but l'll try
to explain what l'm doing. table is a 50x50 array. d1 is the row, d2 the
col.
lea table(PC),a0 ; Let A0 point at the table
mulu #100,d1 ; One row is 100 bytes (50 words). We must use
; MULU to get the right offset. If each row was
; 128 bytes, we could have shifted instead (faster).
adda d1,a0 ; Add the rowoffset to the pointer
lsl.w #1,d2 ; Multiplicate the column with 2 (same reason as above)
move.w 0(a0,d2),d0 ; Get the word and store it in d0 (l wrote this
comment!)
Now: let's say that d0 equals 00000001 (which in my SimTown game l might want
to be the code for a road tile). l know that my label for the sprite can't
start with a number, but l don't want to:
cmp d0,00000001
beq road_tile
cmp d0,00000002
beq clear_land
lnstead, l want to somehow jump to what d0 equals. so when d0 equals 00000001
l want to somehow convert that value into a label it can jump to.
l've been asking a lot of questions lately, but by the help l've received (by
maybe 2-3 people out of the hundred or so on the list) l've been able to learn
some details.
Thank you in advance
--TurboSoft