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2017-08-20 16:28

Trap

Registered: Jul 2010
Posts: 222

How to make efficient double-sine calculations

Hi,

I am trying to improve a little on my effect animation skills. To that purpose I'd like to hear how you guys solve the issue of double-sine table calculations. As I am by no means a math-guru - not even close, try to keep it at a practical level :)
Sure, there has to be some clever way around this. Usually I'd do something like the following mock-up code:

lda Counter1 // Copy counters to indexes
sta Index1
lda Counter2
sta Index2
ldx #TableSize
!CalcAnim: ldy Index1
lda SineWave1,y // Get first value
iny // Index1 Delta + 1
sty Index1
ldy Index2
clc
adc SineWave2,y // Add second value
iny // Index2 Delta + 1
sty Index2
tay
lda Lookuptable,y // Find the value and store it
sta Destinationtable,x
dex
bne CalcAnim-
lda Counter1
clc
adc #1 // Velocity 1
sta Counter1
lda Counter2
clc
adc #1 // Velocity 2
sta Counter2

Apart from unrolling the loop, I am short of good ideas on how to make this efficient. Use of ZP for the indexes saves a few cycles as well.
How do you guys approach this in your demos?

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2017-08-23 13:26

Oswald

Registered: Apr 2002
Posts: 5020

thanks, that makes it clear :)

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