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climb: proper collision detection with bird

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This commit is contained in:
Vince Weaver 2024-09-12 14:18:39 -04:00
parent 148d018253
commit 6fd980e342
2 changed files with 77 additions and 12 deletions
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88
games/peasant_mini/cliff/climb.s
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@ -280,19 +280,10 @@ new_bird_wider:
move_bird:
;=========================
; collision detect here?
; we're both 3 wide
; be lazy and only see if they exactly match?
lda PEASANT_X
cmp bird_x
bne no_bird_collision
; check height
; we are 30 tall
; bird is 15 or so
; collision detect here
jsr bird_collide
bcc no_bird_collision
; collision happened!
@ -639,3 +630,76 @@ peasant_sprites_data_l = peasant_sprite_offset+68
peasant_sprites_data_h = peasant_sprite_offset+102
peasant_mask_data_l = peasant_sprite_offset+136
peasant_mask_data_h = peasant_sprite_offset+170
;===========================
; check for bird collisions
bird_collide:
; bird is 3x16
; peasant is 3x30
; doing a sort of Minkowski Sum collision detection here
; with the rectangular regions
; might be faster to set it up so you can subtract, but that leads
; to issues when we go negative and bcc/bcs are unsigned compares
; if (bird_x+1<PEASANT_X-1) no_collide
; equivalent, if (bird_x+2<PEASANT_X)
; equivalent, if (PEASANT_X-1 >= bird_x+1)
lda bird_x
sta TEMP_CENTER
inc TEMP_CENTER ; bird_x+1
sec
lda PEASANT_X
sbc #1 ; A is PEASANT_X-1
cmp TEMP_CENTER ; compare with bird_x+1
bcs bird_no_collide ; bge
; if (bird_x+1>=PEASANT_X+3) no collide
; equivalent, if (bird_x-2>=PEASANT_X)
; equivalent, if (PEASANT_X+3<bird_x+1)
; carry clear here
adc #4 ; A is now PEASANT_X+3
cmp TEMP_CENTER
bcc bird_no_collide ; blt
; if (bird_y+8<PEASANT_Y-8) no_collide
; equivalent, if (bird_y+16<PEASANT_Y)
; equivalent, if (PEASANT_Y-8>=bird_y+8)
lda bird_y
clc
adc #8
sta TEMP_CENTER
lda PEASANT_Y
sec
sbc #8 ; A is now PEASANT_Y-8
cmp TEMP_CENTER
bcs bird_no_collide ; blt
; if (bird_Y+8>=PEASANT_Y+38) no collide
; equivalent, if (bird_y-30>=PEASANT_Y)
; equivalent, if (PEASANT_Y+38<bird_y+8)
; carry clead here
adc #38 ; A is now bird_y+30
cmp TEMP_CENTER
bcc bird_no_collide ; blt
bird_yes_collide:
sec
rts
bird_no_collide:
clc
rts

1
games/peasant_mini/cliff/zp.inc
View File

@ -275,6 +275,7 @@ CURRENT_DISK = $DC
HGR_COLOR = $E4
HGR_PAGE = $E6
TEMP_CENTER = $EC
CLIMB_COUNT = $ED
FLAME_COUNT = $EE
CURRENT_ROCK = $EF