# dimensions in games

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hi i wonder what dimensions are usually used in 3d games and in what range the values lie. are these values taken in account with physics calculations? has anyone experience with this? thanks gerold

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Only remember two, which are(IIRC):

Quake: 1 unit = 1 inch, -16384 to 16383
Serious Sam: 1 unit = 1 meter, whatever a float(or was it double?) can hold

I'd prefer the latter. Makes for easier use aswell since all constants in our physics lookup tables are metric.

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ok, that's what i thought.

another question:
are there any pros/cons using a world coordinate system only
at the positive axes or one using positive and negative axes?

thanks, gerold

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what do you mean by that?

you mean, X going right, Y going up, Z going through the screen?

That makes up for a left-handed coordinate system, which is usually a bad idea. So either, put Y down, or Z coming towards you, to get a right handed coordinate system.

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I think he means, should the world lie entirely in the positive octant? Or should it be centered at the origin?

Off the top of my head, I can't think of a reason why one would be better than the other.

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Quote:
 Original post by jykOff the top of my head, I can't think of a reason why one would be better than the other.
How about increased floating-point precision towards the origin?
Placing the origin at the worlds center should improve the average precision.

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Quote:
 Original post by jykOff the top of my head, I can't think of a reason why one would be better than the other.

Floating point precision is expressed in terms of significant digits. You have better precision at the origin than 1e9 away from it.

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ok thanks, that what i wanted to know.
you guys are really fast :)

gerold

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