Apple-2gs-SW/iigs-game-engine
1
0
Fork 0
mirror of https://github.com/lscharen/iigs-game-engine.git synced 2024-11-26 07:49:17 +00:00
Code Issues Projects Releases Wiki Activity

Make sure all macros add the vbuff offsets

Browse Source
This commit is contained in:
Lucas Scharenbroich 2022-06-07 10:05:52 -05:00
parent 3591c494bf
commit 1de4c0bc7f
1 changed files with 8 additions and 68 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

76
src/Tiles.s
View File

@ -269,10 +269,14 @@ dobit mac
beq last_bit
tax
lda (SPRITE_VBUFF_PTR+{]1*2}),y
clc
adc _Sprites+TS_VBUFF_BASE+{]1*2}
sta sprite_ptr0+{]2*4}
txa
jmp ]3
last_bit lda (SPRITE_VBUFF_PTR+{]1*2}),y
clc ; pre-adjust these later
adc _Sprites+TS_VBUFF_BASE+{]1*2}
sta sprite_ptr0+{]2*4}
jmp ]4
next_bit
@ -299,79 +303,13 @@ last_bit lda (SPRITE_VBUFF_PTR+{]1*2}),y
next_bit
<<<
; Optimization discussion. In the Sprite2.s file, we calculate the VBUFF address for each tile overlapped
; by a sprite:
;
; 4 lda VBuffOrigin
; 3 adc ]2
; 7 sta [tmp0],y
;
; and then in this macro it is loaded again and copied to the direct page. If a sprite is never drawn, this is
; wasted work (which is not too ofter since >4 sprites would need to be overlapping), but still.
;
; 6 ldy: {]1*TILE_STORE_SIZE},x
; 4 sty sprite_ptr0+{]2*4}
;
; Since we know *exactly* which sprite is being accessed, the _Sprites+TS_VBUFF_BASE,y value can be loaded without
; an index
;
; 5 lda _Sprites+TS_VBUFF_BASE+{]1*2}
; 6 adc {]1*TILE_STORE_SIZE},x
; 4 sta sprite_ptr0+{]2*4}
; 2 tya
;
; = a savings of at least (24 - 17) = 7 cycles per tile and more if the sprite is skipped.
;
; The problem is that this still required storing a value for the sprite in the tile store. What is ideal is
; if there is a way to know implicitly which relative tile offset we are on for a given sprite and use
; that to calculate the offset...
;
; What do we know
; X = current tile
; Sprite+TS_LOOKUP_INDEX
;
; txa
; sbc _Sprites+TS_LOOKUP_INDEX+{]1*2}
; tay
; lda _Sprites+TS_VBUFF_BASE+{]1*2}
; adc DisplacementTable,y
; sta sprite_ptr0+{]2*4}
;
; Have the sprite select a table base which holds the offset values, pre-adjusted for the TS_LOOKUP_INDEX. The table
; values are fixed. Yes!! This is the solution!! It will only need 288 bytes of total space
;
; Best implementation will pass the Tile Store index in Y instead of X
;
; 5 lda _Sprites+VBUFF_TABLE+{]1*2}
; 6 sta self_mod
; 6 lda $0000,x
; 4 sta sprite_ptr0+{]2*4}
; 2 tya
;
; or
;
; 5 lda _Sprites+VBUFF_TABLE+{]1*2}
; 4 sta tmp0
; 7 lda (tmp0),y
; 4 sta sprite_ptr0+{]2*4}
; 2 txa
;
; Even better, if the VBUFF_TABLE (only 32 bytes) was already stored in the second direct page
;
; 7 lda (VBUFF_TABLE+{]1*2}),y
; 5 adc _Sprites+VBUFF_TABLE+{]1*2}
; 4 sta sprite_ptr0+{]2*4}
; 2 txa
;
; Final saving compared to current implementation is (24 - 18) = 6 cycles per tile and we eliminate
; the need to pre-calculate
;
; If we find a last bit (4th in this case) and will exit
stpbit mac
lsr
bcc next_bit
lda (SPRITE_VBUFF_PTR+{]1*2}),y
clc ; pre-adjust these later
adc _Sprites+TS_VBUFF_BASE+{]1*2}
sta sprite_ptr0+{]2*4}
jmp ]3
next_bit
@ -380,6 +318,8 @@ next_bit
; Last bit test which *must* be set
endbit mac
lda (SPRITE_VBUFF_PTR+{]1*2}),y
clc ; pre-adjust these later
adc _Sprites+TS_VBUFF_BASE+{]1*2}
sta sprite_ptr0+{]2*4}
jmp ]3
<<<