GSCats/collision.s
2017-10-09 14:41:05 -07:00

119 lines
2.0 KiB
ArmAsm

;
; collision
;
; Created by Quinn Dunki on 9/2/17
;
rectParams:
.word 0 ; x
.word 0 ; y 0=terrain bottom, +y=up
.word 0 ; w
.word 0 ; h
rectParams2:
.word 0 ; x
.word 0 ; y 0=terrain bottom, +y=up
.word 0 ; w
.word 0 ; h
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
; intersectRectTerrain
;
; A => non zero if rectangle is intersecting terrain
;
intersectRectTerrain:
phy
; Convert X to words and compute horizontal extent
; Note that X counts from right terrain edge
lda rectParams
and #$fffe ; Force even
sta rectParams
lda #TERRAINWIDTH ; Reverse X coordinate system
sec
sbc rectParams
sta rectParams
tay ; We'll need this later as an index into height data words
sec
sbc rectParams+4 ; Convert width to extent
sta rectParams+4
; Convert height to vertical extent
lda rectParams+2
sec
sbc rectParams+6
sta rectParams+6
; Check Y bottom
intersectRectTerrainBottomLoop:
lda terrainData,y
cmp rectParams+6
bpl intersectRectTerrainYep
dey
dey
cpy rectParams+4
bpl intersectRectTerrainBottomLoop
lda #0
ply
rts
intersectRectTerrainYep:
lda #1
ply
rts
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
; intersectRectRect
;
; A => non zero if rectangle is intersecting rectangle2
;
intersectRectRect:
lda rectParams+0 ; Convert widths to extents
clc
adc rectParams+4
sta rectParams+4
lda rectParams2+0
clc
adc rectParams2+4
sta rectParams2+4
lda rectParams+2 ; Convert heights to extents
sec
sbc rectParams+6
sta rectParams+6
lda rectParams2+2
sec
sbc rectParams2+6
sta rectParams2+6
lda rectParams+0 ; Past their right edge?
cmp rectParams2+4
bpl intersectRectRectNope
lda rectParams+4 ; Before their left edge?
cmp rectParams2+0
bmi intersectRectRectNope
lda rectParams+2 ; Past their bottom edge?
cmp rectParams2+6
bmi intersectRectRectNope
lda rectParams+6 ; Before their top edge?
cmp rectParams2+2
bpl intersectRectRectNope
lda #1
rts
intersectRectRectNope:
lda #0
rts