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bit shifting and isometrics engines..


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#1 Sphet   Members   -  Reputation: 631

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Posted 16 September 1999 - 02:20 PM

I'm trying to remember where I read this and how it is applied.

When trying to calculate the position offset for blitting tiles, someone suggested bitshifting the values because they're faster than multiplies. I can neither remember who wrote this, or what it was about. Anyone remember which of the original Iso tutorials/articles this was from and what it was about?


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#2 Dragun   Members   -  Reputation: 123

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Posted 16 September 1999 - 09:22 AM

Bitshifting only applies if the tile x and y offsets are a multiple of 2 (like a 64x31 tile).

#3 Sphet   Members   -  Reputation: 631

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Posted 16 September 1999 - 12:35 PM

Dragon,

Can you explain to me a bit how this works?


#4 Anonymous Poster_Anonymous Poster_*   Guests   -  Reputation:

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Posted 16 September 1999 - 01:19 PM

a bit shift once to the left is equal to muliplying by 2, only faster. so if you bit shift 4 to the left, it's *2*2*2*2, or, *16. In other words, 4 << 3 = 4*2*2*2 = 32

#5 Sphet   Members   -  Reputation: 631

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Posted 16 September 1999 - 01:50 PM

Thanks guys.

#6 Jim Adams   Members   -  Reputation: 440

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Posted 16 September 1999 - 02:20 PM

You can also bit shift and add the values to come up with others, for instance, to multiply a number by 320:
newvalue = (val << 8) + (val << 6);





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