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# Matrices

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I am wondering what do these matrix values mean i got these from a game and they are from an Inertial Matrix what is on of them? here are the values yy+zz -xy -zx -xy zz+xx -yz -zx -zy xx+yy Does anyone know what they do? this was in the physics tag.

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Google 'inertia matrix', or read some introductory articles or books on physics.

The inertia matrix has a similar relationship to angular motion that mass does to linear motion. Mass can be viewed as a measure of how 'hard' it is to impart linear motion to an object, as reflected in the equation:

a = F/m

The equations for angular motion are a bit more complicated, but the inertia matrix can be viewed as a measure of how hard it is to get an object rotating about a particular axis.

This is an informal definition; also, I'm not a physics expert so don't take anything I say here as the final word.

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The inertia matrix is used in the equation for moment of inertia of a solid body.

Basically, like jyk said, the moment of inertia is the rotational analogue of mass.

The greater the moment of inertia, the more difficult it is to rotate the body.

Wikipedia has a less technical explanation here.

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These are the values in the engine

yy+zz -xy -zx i 189.408 i -6.1512e-007 k 5.712
-xy zz+xx -yz i -6.1512e-007 i 301.6 k -4.76836e-009
-zx -zy xx+yy i 5.712 i -4.76836e-00 k 423.648

I don't know what the i and k mean but they are on the text fields. So what does the above do can someone explain? thanks.

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They already gave you more information than you deserved; nilkn gave you two links and someone else said to check google.

If you can't learn on your own then your always going to be lost.

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But i don't understand all them symbols.

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Quote:
 Original post by GameMasterXLBut i don't understand all them symbols.

In this case, all I can tell you is that the inertia matrix is useful in calculating the moment of inertia of a solid body, and that the moment of inertia is a quantity telling you how resistant a body is to angular acceleration.

If you really want to understand it thoroughly, you'll have to spend some time learning what all those symbols mean (which, if you don't know any of them, is no small task[smile])

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