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examples: new sprite animation demo

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slederer 2025-06-20 01:19:40 +02:00
parent bde01e402c
commit e08d610aef
6 changed files with 186 additions and 24 deletions
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55
examples/sprites.s
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@ -1,4 +1,5 @@
.EQU SPRITE_HEIGHT 16
.EQU SPRITE_HEIGHT 32 ; height in lines
.EQU SPRITE_STRIPES 4 ; width in words i.e. 8-pixel stripes
.EQU WORDS_PER_LINE 80
.EQU FB_RA $900
@ -65,7 +66,8 @@ CALC_VMEM_ADDR:
.EQU PS_Y 16
.EQU PS_SHIFT_C 20
.EQU PS_SPILL 24
.EQU PS_FS 28
.EQU PS_STRIPE_C 28
.EQU PS_FS 32
PUTSPRITE:
FPADJ -PS_FS
STORE PS_SPRITE_DATA
@ -160,10 +162,14 @@ PS_LOOP2_X:
STOREI ; store result into i/o reg
DROP
;
; process spilled bits and right half of sprite data
;
; set counter for remaining stripes
LOADC SPRITE_STRIPES - 1
STORE PS_STRIPE_C
;
; process spilled bits and next vertical stripe of sprite data
;
PS_NEXT_STRIPE:
; put spill bits on stack for later
LOAD PS_SPILL
@ -176,7 +182,9 @@ PS_LOOP2_X:
; reset spill bits
LOADC 0
STORE PS_SPILL
; last spill bits are on ToS now
; shift pixel data to right
LOAD PS_SHIFT_C ; load shift count
PS_LOOP3: ; test it for zero
@ -230,8 +238,14 @@ PS_LOOP3_X:
SWAP
STOREI
DROP
; write spilled bits into next vmem word
LOAD PS_STRIPE_C ; decrement stripe count
DEC 1
DUP
STORE PS_STRIPE_C
CBRANCH.NZ PS_NEXT_STRIPE ; if non-zero, next stripe
; write spilled bits of the last stripe into next vmem word
LOAD PS_SPILL ; get spill bits
DUP
LOADCP CALC_MASK ; calculate sprite mask for spill bits
@ -274,7 +288,8 @@ PS_L_XT:
.EQU UD_S_BGDATA 12
.EQU UD_S_OFFSET 16
.EQU UD_S_BGORIG 20
.EQU UD_S_FS 24
.EQU UD_STRIPE_C 24
.EQU UD_S_FS 28
UNDRAWSPRITE:
FPADJ -UD_S_FS
STORE UD_S_BGORIG
@ -318,25 +333,35 @@ UD_S_L1:
STOREI
; reuse addr from STOREI
; load 2nd word of background data
LOADC SPRITE_STRIPES - 1 ; set remaining stripe count
STORE UD_STRIPE_C
UD_NEXT_STRIPE:
; load next word of background data
LOAD UD_S_BGDATA
INC 4
DUP
STORE UD_S_BGDATA
LOADI
STOREI ; and write it to vmem
DROP
; reuse addr from STOREI
; if pixel shift is zero, no 3rd word
LOAD UD_STRIPE_C ; decrease remaining stripe count
DEC 1
DUP
STORE UD_STRIPE_C
CBRANCH.NZ UD_NEXT_STRIPE ; if non-zero, next stripe
DROP ; remove addr from STOREI
; if pixel shift is zero, no spill word
LOAD UD_S_PXS
CBRANCH.Z UD_S_L2
; load 3rd word of background data
; load next word of background data
LOADCP FB_IO
LOAD UD_S_BGDATA
INC 4
DUP
STORE UD_S_BGDATA
LOADI
STOREI ; and write it to vmem
DROP