Linked by Thom Holwerda on Tue 18th Dec 2012 23:12 UTC
Windows "Windows XP was the last client version of Windows to include the Pinball game that had been part of Windows since Windows 95. There is apparently speculation that this was done for legal reasons. No, that's not why." I love these stories.
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RE[2]: read the comments
by Alfman on Thu 20th Dec 2012 13:14 UTC in reply to "RE: read the comments"
Alfman
Member since:
2011-01-28

renox,

"Sigh, and people still look at me as if I was a madman when I say that floating point suck and that we should use interval arithmetic.."

Very insightful. Beyond rounding issues, it's always bugged me a bit too that the resolution of game coordinates become worse and worse the further a player gets away from the origin. Therefor if your running precise mathematical computations in a game (ie object projections), the results inherently depend on which arbitrary digits the mantissa is representing. Using integral/fixed point arithmetic would offer equal precision at all coordinates.

Reply Parent Score: 2

RE[3]: read the comments
by renox on Thu 20th Dec 2012 15:43 in reply to "RE[2]: read the comments"
renox Member since:
2005-07-06

That's a different issue but you're right also I remember reading game developers advocating fixed point arithmetic for world coordinate.
One can do interval arithmetic with fixed point computation too..

Reply Parent Score: 2

RE[4]: read the comments
by Alfman on Thu 20th Dec 2012 16:26 in reply to "RE[3]: read the comments"
Alfman Member since:
2011-01-28

renox,

Floating point used to be far more accurate than ints when cpu registers were limited to 32bit. Now that we have 64bit registers and SSE's FP mantissa is only 52bits, fixed point integers can give us more accuracy as well.

I wonder if there are any game worlds that are big enough such that this makes an observable difference?

If each object were tracked to millimetre resolution, then SSE's 64bit FP is accurate up to half a light year in any direction. 64bit signed fixed point would cover 970 light years in any direction.

So I guess there's probably not a very compelling reason to switch unless your simulating a large universe.

Nice chart showing breakdown of FP formats.
http://www.monash.edu.au/policy/gpnumacc.htm

Reply Parent Score: 2