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Added shot power & fixed point multiply

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blondie7575 2017-09-05 12:07:33 -07:00
parent dec9f3e2c8
commit 4525010273
4 changed files with 83 additions and 5 deletions
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BIN
gscats.2mg
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6
player.s
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@ -13,7 +13,7 @@ playerData:
.word 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0 ; Saved background
.word 45 ; Angle in degrees from +X
.word 50 ; Power
.word 2 ; Power
.word 100 ; Anger
.byte 8,"SPROCKET " ; Name
.word 0,0,0,0,0,0 ;Padding
@ -23,8 +23,8 @@ playerData:
.word 0 ; Y pos in pixels (from bottom terrain edge)
.word 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0 ; Saved background
.word 45 ; Angle in degrees from +X
.word 50 ; Power
.word 135 ; Angle in degrees from +X
.word 3 ; Power
.word 100 ; Anger
.byte 8,"TINKER " ; Name
.word 0,0,0,0,0,0 ;Padding

24
projectile.s
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@ -90,16 +90,36 @@ fireProjectile:
asl
sta projectileData+JD_PRECISEY,y
lda projectileParams+6 ; Convert power to 8.8
asl
asl
asl
asl
asl
asl
asl
asl
sta projectileParams+6
lda projectileParams+4 ; Convert angle to vector
asl
tax
lda angleToVectorX,x ; Velocity X
lda angleToVectorX,x ; Velocity X (unit vector)
sta PARAML1
lda projectileParams+6 ; Scale by power
sta PARAML0
jsr mult88
sta projectileData+JD_VX,y
lda projectileParams+4 ; Convert angle to vector
asl
tax
lda angleToVectorY,x ; Velocity Y
lda angleToVectorY,x ; Velocity Y (unit vector)
sta PARAML1
lda projectileParams+6 ; Scale by power
sta PARAML0
jsr mult88
sta projectileData+JD_VY,y
RESTORE_AXY

58
utility.s
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@ -61,6 +61,8 @@ intToStringSkipSingle:
sta intToStringResult,y
iny
inx
cpx #3
beq intToStringFinish ; Single digit number so we're done
intToStringFullDigitsLoop:
; Remaining bytes all contain two digits
@ -83,6 +85,7 @@ intToStringFullDigitsLoop:
cpx #3
bne intToStringFullDigitsLoop
intToStringFinish:
; Store final length and we're done
dey
sty intToStringResult
@ -94,3 +97,58 @@ intToStringDone:
intToStringBCD: .byte 0,0,0
intToStringResult: .byte 0,0,0,0,0,0
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
; mult16
;
; PARAML0 = Operand 1 (16 bits)
; PARAML1 = Operand 2 (16 bits)
; A => Op1 * Op2 (16 bits)
; Algorithm from https://apple2.gs/downloads/Programmanual.pdf
; Trashes X
;
mult16:
lda #0 ; Initialize result
mult16L1:
ldx PARAML0 ; Get operand 1
beq mult16Done ; If operand is zero, we're done
lsr PARAML0 ; Get low bit
bcc mult16L2 ; If clear, no additions to previous products
clc ; Otherwise add oeprand 2 to partial result
adc PARAML1
mult16L2:
asl PARAML1 ; Now shift operand 2 left for possible add next time
bra mult16L1
mult16Done:
rts
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
; mult88
;
; PARAML0 = Operand 1 (8.8 fixed point)
; PARAML1 = Operand 2 (8.8 fixed point)
; A => Op1 * Op2 (8.8 fixed point)
; Substantial precision loss occurs here, but it's usually good enough
;
mult88:
lda PARAML0 ; Convert operands to 12.4
lsr
lsr
lsr
lsr
sta PARAML0
lda PARAML1
lsr
lsr
lsr
lsr
sta PARAML1
jsr mult16 ; Result is 8.8
rts