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8bitworkshop/presets/vcs/ecs/velocity.ecs
2022-06-30 13:31:29 -05:00

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//#resource "vcs-ca65.h"
import "vcslib.ecs"
import "sprites.ecs"
component TinyVelX
// TODO: -8..7? packed?
xvel: 0..15 default 8
end
component TinyVelY
// TODO: -8..7? packed?
yvel: 0..15 default 8
end
system TinyMover
locals 1
on postframe do foreach [HasXpos,TinyVelX]
---
lda {{<FrameCount:frame}}
and #7 ; reduce frame # to 0..7
tay
lda {{^VMaskTable}},y ; lookup frame bit mask
ldy {{<xvel}} ; xvel from 0..15
and {{^VAndTable}},y ; mask with velocity table
jeq @nomove ; no bits set? no move
lda {{^DeltaVTable}},y ; lookup position delta
clc
adc {{<xpos}} ; add to coordinate
sta {{<xpos}} ; store to coordinate
{{!xmoved}} ; maybe modify it?
@nomove:
---
on postframe do foreach [HasXpos,TinyVelY]
---
lda {{<FrameCount:frame}}
and #7 ; reduce frame # to 0..7
tay
lda {{^VMaskTable}},y ; lookup frame bit mask
ldy {{<yvel}} ; xvel from 0..15
and {{^VAndTable}},y ; mask with velocity table
jeq @nomove ; no bits set? no move
lda {{^DeltaVTable}},y ; lookup position delta
clc
adc {{<ypos}} ; add to coordinate
sta {{<ypos}} ; store to coordinate
{{!ymoved}} ; maybe modify it?
@nomove:
---// set player reflection bit
on xmoved do with [Sprite]
---
pha
lda {{<plyrflags}}
and #255-8
ora {{^VReflectTab}},y
sta {{<plyrflags}}
and #7
tay
lda {{^VXLimitTab}},y
sta {{$0}}
pla
---
// TODO: x/y limits should be properties
on xmoved do with [HasXpos]
---
cmp #2
jcc @left
cmp {{$0}}
jcc @skip
@right:
{{!xlimit_right}}
jne @skip
@left:
{{!xlimit_left}}
@skip:
---
on xlimit_right do with [HasXpos]
---
lda {{$0}}
sta {{<xpos}}
---
on xlimit_left do with [HasXpos]
---
lda #2
sta {{<xpos}}
---
end
resource DeltaVTable ---
; this table tells us which direction to move
; for each of the 16 velocity values (-1, 0 or +1)
.byte $fe,$fe,$ff,$ff,$ff,$ff,$ff,$00
.byte $00,$01,$01,$01,$01,$01,$02,$02
---
resource VAndTable ---
; this table contains a bitmask for each of the 16
; velocity values -- it's ANDed with a global shift
; register that tells us which frames to update position
.byte %11111111 ;16/8
.byte %01110111 ;12/8
.byte %11111111 ;8/8
.byte %01110111 ;6/8
.byte %10101010 ;4/8
.byte %01010010 ;3/8
.byte %10001000 ;2/8
.byte %00000000 ;0
.byte %00000000 ;0
.byte %10001000 ;2/8
.byte %01010010 ;3/8
.byte %10101010 ;4/8
.byte %01110111 ;6/8
.byte %11111111 ;8/8
.byte %01110111 ;12/8
.byte %11111111 ;16/8
---
resource VMaskTable ---
.byte %00000001
.byte %00000010
.byte %00000100
.byte %00001000
.byte %00010000
.byte %00100000
.byte %01000000
.byte %10000000
---
resource VReflectTab ---
.byte 8,8,8,8,8,8,8,8
.byte 0,0,0,0,0,0,0,0
---
/*
if 000, X one copy
if 001, X X two copies, close
if 010, X X two copies, medium
if 011, X X X three copies, close
if 100, X X Two copies, far
if 101, XX one copy, double width
if 110, X X X 3 copies, medium
if 111, XXXX one copy, quad width
*/
resource VXLimitTab ---
.byte 152-8*1
.byte 152-8*3
.byte 152-8*5
.byte 152-8*5
.byte 152-8*9
.byte 152-8*2
.byte 152-8*9
.byte 152-8*4
---