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Add subdirectories to engine/ similar to pokecrystal
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Rangi
parent
5559d51c86
commit
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124 changed files with 342 additions and 346 deletions
356
engine/overworld/sprite_collisions.asm
Normal file
356
engine/overworld/sprite_collisions.asm
Normal file
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@ -0,0 +1,356 @@
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_UpdateSprites::
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ld h, $c1
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inc h
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ld a, $e ; wSpriteStateData2 + $0e
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.spriteLoop
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ld l, a
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sub $e
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ld c, a
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ld [H_CURRENTSPRITEOFFSET], a
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ld a, [hl]
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and a
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jr z, .skipSprite ; tests $c2Xe
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push hl
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push de
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push bc
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call .updateCurrentSprite
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pop bc
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pop de
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pop hl
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.skipSprite
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ld a, l
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add $10 ; move to next sprite
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cp $e ; test for overflow (back at $0e)
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jr nz, .spriteLoop
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ret
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.updateCurrentSprite
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cp $1
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jp nz, UpdateNonPlayerSprite
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jp UpdatePlayerSprite
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UpdateNonPlayerSprite:
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dec a
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swap a
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ld [$ff93], a ; $10 * sprite#
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ld a, [wNPCMovementScriptSpriteOffset] ; some sprite offset?
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ld b, a
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ld a, [H_CURRENTSPRITEOFFSET]
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cp b
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jr nz, .unequal
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jp DoScriptedNPCMovement
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.unequal
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jp UpdateNPCSprite
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; This detects if the current sprite (whose offset is at H_CURRENTSPRITEOFFSET)
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; is going to collide with another sprite by looping over the other sprites.
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; The current sprite's offset will be labelled with i (e.g. $c1i0).
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; The loop sprite's offset will labelled with j (e.g. $c1j0).
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;
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; Note that the Y coordinate of the sprite (in [$c1k4]) is one of the following
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; 9 values when the sprite is aligned with the grid: $fc, $0c, $1c, $2c, ..., $7c.
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; The reason that 4 is added below to the coordinate is to make it align with a
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; multiple of $10 to make comparisons easier.
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DetectCollisionBetweenSprites:
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nop
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ld h, wSpriteStateData1 / $100
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ld a, [H_CURRENTSPRITEOFFSET]
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add wSpriteStateData1 % $100
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ld l, a
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ld a, [hl] ; a = [$c1i0] (picture) (0 if slot is unused)
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and a ; is this sprite slot slot used?
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ret z ; return if not used
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ld a, l
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add 3
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ld l, a
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ld a, [hli] ; a = [$c1i3] (delta Y) (-1, 0, or 1)
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call SetSpriteCollisionValues
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ld a, [hli] ; a = [$C1i4] (Y screen coordinate)
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add 4 ; align with multiple of $10
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; The effect of the following 3 lines is to
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; add 7 to a if moving south or
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; subtract 7 from a if moving north.
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add b
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and $f0
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or c
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ld [$ff90], a ; store Y coordinate adjusted for direction of movement
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ld a, [hli] ; a = [$c1i5] (delta X) (-1, 0, or 1)
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call SetSpriteCollisionValues
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ld a, [hl] ; a = [$C1i6] (X screen coordinate)
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; The effect of the following 3 lines is to
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; add 7 to a if moving east or
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; subtract 7 from a if moving west.
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add b
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and $f0
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or c
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ld [$ff91], a ; store X coordinate adjusted for direction of movement
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ld a, l
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add 7
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ld l, a
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xor a
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ld [hld], a ; zero [$c1id] XXX what's [$c1id] for?
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ld [hld], a ; zero [$c1ic] (directions in which collisions occurred)
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ld a, [$ff91]
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ld [hld], a ; [$c1ib] = adjusted X coordinate
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ld a, [$ff90]
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ld [hl], a ; [$c1ia] = adjusted Y coordinate
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xor a ; zero the loop counter
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.loop
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ld [$ff8f], a ; store loop counter
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swap a
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ld e, a
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ld a, [H_CURRENTSPRITEOFFSET]
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cp e ; does the loop sprite match the current sprite?
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jp z, .next ; go to the next sprite if they match
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ld d, h
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ld a, [de] ; a = [$c1j0] (picture) (0 if slot is unused)
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and a ; is this sprite slot slot used?
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jp z, .next ; go the next sprite if not used
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inc e
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inc e
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ld a, [de] ; a = [$c1j2] ($ff means the sprite is offscreen)
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inc a
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jp z, .next ; go the next sprite if offscreen
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ld a, [H_CURRENTSPRITEOFFSET]
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add 10
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ld l, a
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inc e
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ld a, [de] ; a = [$c1j3] (delta Y)
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call SetSpriteCollisionValues
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inc e
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ld a, [de] ; a = [$C1j4] (Y screen coordinate)
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add 4 ; align with multiple of $10
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; The effect of the following 3 lines is to
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; add 7 to a if moving south or
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; subtract 7 from a if moving north.
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add b
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and $f0
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or c
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sub [hl] ; subtract the adjusted Y coordinate of sprite i ([$c1ia]) from that of sprite j
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; calculate the absolute value of the difference to get the distance
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jr nc, .noCarry1
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cpl
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inc a
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.noCarry1
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ld [$ff90], a ; store the distance between the two sprites' adjusted Y values
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; Use the carry flag set by the above subtraction to determine which sprite's
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; Y coordinate is larger. This information is used later to set [$c1ic],
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; which stores which direction the collision occurred in.
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; The following 5 lines set the lowest 2 bits of c, which are later shifted left by 2.
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; If sprite i's Y is larger, set lowest 2 bits of c to 10.
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; If sprite j's Y is larger or both are equal, set lowest 2 bits of c to 01.
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push af
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rl c
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pop af
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ccf
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rl c
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; If sprite i's delta Y is 0, then b = 7, else b = 9.
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ld b, 7
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ld a, [hl] ; a = [$c1ia] (adjusted Y coordinate)
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and $f
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jr z, .next1
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ld b, 9
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.next1
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ld a, [$ff90] ; a = distance between adjusted Y coordinates
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sub b
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ld [$ff92], a ; store distance adjusted using sprite i's direction
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ld a, b
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ld [$ff90], a ; store 7 or 9 depending on sprite i's delta Y
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jr c, .checkXDistance
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; If sprite j's delta Y is 0, then b = 7, else b = 9.
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ld b, 7
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dec e
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ld a, [de] ; a = [$c1j3] (delta Y)
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inc e
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and a
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jr z, .next2
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ld b, 9
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.next2
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ld a, [$ff92] ; a = distance adjusted using sprite i's direction
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sub b ; adjust distance using sprite j's direction
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jr z, .checkXDistance
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jr nc, .next ; go to next sprite if distance is still positive after both adjustments
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.checkXDistance
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inc e
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inc l
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ld a, [de] ; a = [$c1j5] (delta X)
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push bc
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call SetSpriteCollisionValues
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inc e
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ld a, [de] ; a = [$c1j6] (X screen coordinate)
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; The effect of the following 3 lines is to
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; add 7 to a if moving east or
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; subtract 7 from a if moving west.
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add b
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and $f0
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or c
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pop bc
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sub [hl] ; subtract the adjusted X coordinate of sprite i ([$c1ib]) from that of sprite j
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; calculate the absolute value of the difference to get the distance
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jr nc, .noCarry2
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cpl
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inc a
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.noCarry2
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ld [$ff91], a ; store the distance between the two sprites' adjusted X values
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; Use the carry flag set by the above subtraction to determine which sprite's
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; X coordinate is larger. This information is used later to set [$c1ic],
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; which stores which direction the collision occurred in.
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; The following 5 lines set the lowest 2 bits of c.
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; If sprite i's X is larger, set lowest 2 bits of c to 10.
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; If sprite j's X is larger or both are equal, set lowest 2 bits of c to 01.
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push af
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rl c
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pop af
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ccf
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rl c
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; If sprite i's delta X is 0, then b = 7, else b = 9.
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ld b, 7
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ld a, [hl] ; a = [$c1ib] (adjusted X coordinate)
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and $f
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jr z, .next3
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ld b, 9
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.next3
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ld a, [$ff91] ; a = distance between adjusted X coordinates
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sub b
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ld [$ff92], a ; store distance adjusted using sprite i's direction
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ld a, b
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ld [$ff91], a ; store 7 or 9 depending on sprite i's delta X
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jr c, .collision
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; If sprite j's delta X is 0, then b = 7, else b = 9.
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ld b, 7
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dec e
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ld a, [de] ; a = [$c1j5] (delta X)
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inc e
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and a
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jr z, .next4
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ld b, 9
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.next4
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ld a, [$ff92] ; a = distance adjusted using sprite i's direction
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sub b ; adjust distance using sprite j's direction
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jr z, .collision
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jr nc, .next ; go to next sprite if distance is still positive after both adjustments
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.collision
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ld a, [$ff91] ; a = 7 or 9 depending on sprite i's delta X
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ld b, a
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ld a, [$ff90] ; a = 7 or 9 depending on sprite i's delta Y
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inc l
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; If delta X isn't 0 and delta Y is 0, then b = %0011, else b = %1100.
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; (note that normally if delta X isn't 0, then delta Y must be 0 and vice versa)
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cp b
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jr c, .next5
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ld b, %1100
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jr .next6
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.next5
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ld b, %0011
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.next6
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ld a, c ; c has 2 bits set (one of bits 0-1 is set for the X axis and one of bits 2-3 for the Y axis)
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and b ; we select either the bit in bits 0-1 or bits 2-3 based on the calculation immediately above
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or [hl] ; or with existing collision direction bits in [$c1ic]
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ld [hl], a ; store new value
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ld a, c ; useless code because a is overwritten before being used again
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; set bit in [$c1ie] or [$c1if] to indicate which sprite the collision occurred with
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inc l
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inc l
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ld a, [$ff8f] ; a = loop counter
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ld de, SpriteCollisionBitTable
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add a
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add e
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ld e, a
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jr nc, .noCarry3
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inc d
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.noCarry3
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ld a, [de]
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or [hl]
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ld [hli], a
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inc de
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ld a, [de]
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or [hl]
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ld [hl], a
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.next
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ld a, [$ff8f] ; a = loop counter
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inc a
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cp $10
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jp nz, .loop
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ret
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; takes delta X or delta Y in a
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; b = delta X/Y
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; c = 0 if delta X/Y is 0
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; c = 7 if delta X/Y is 1
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; c = 9 if delta X/Y is -1
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SetSpriteCollisionValues:
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and a
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ld b, 0
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ld c, 0
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jr z, .done
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ld c, 9
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cp -1
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jr z, .ok
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ld c, 7
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ld a, 0
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.ok
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ld b, a
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.done
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ret
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SpriteCollisionBitTable:
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db %00000000,%00000001
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db %00000000,%00000010
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db %00000000,%00000100
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db %00000000,%00001000
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db %00000000,%00010000
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db %00000000,%00100000
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db %00000000,%01000000
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db %00000000,%10000000
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db %00000001,%00000000
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db %00000010,%00000000
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db %00000100,%00000000
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db %00001000,%00000000
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db %00010000,%00000000
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db %00100000,%00000000
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db %01000000,%00000000
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db %10000000,%00000000
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