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the default coordinate system of model, right-handed or left-handed?


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#1 sobeit   Members   -  Reputation: 433

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Posted 22 February 2013 - 04:26 PM

hi there,

 

I have a question, as mentioned in the title, in which coordinate system(left-handed or right-handed) are those common 3d-model formats(3dmax, obj) built? 

I have this question because I need to do some back face culling work, which involves vertices triangle winding direction which would be reversed if the coordinate system of an original model is different from the one the model is being transformed.

 

Thanks,

 



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#2 blackpawn   Members   -  Reputation: 193

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Posted 22 February 2013 - 06:52 PM

i think every DCC like max, maya, modo, houdini, xsi, etc are all right handed. can't remember ever using one that was left handed. they may still assume different windings orders though.



#3 sobeit   Members   -  Reputation: 433

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Posted 22 February 2013 - 10:45 PM

i think every DCC like max, maya, modo, houdini, xsi, etc are all right handed. can't remember ever using one that was left handed. they may still assume different windings orders though.

But why direct3d use left-handed transformation system? OpenGL use right-handed system but convert it to left-handed in normalized-device-coordinate.


Edited by sobeit, 22 February 2013 - 10:47 PM.


#4 Hodgman   Moderators   -  Reputation: 30387

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Posted 23 February 2013 - 12:03 AM

i think every DCC like max, maya, modo, houdini, xsi, etc are all right handed. can't remember ever using one that was left handed. they may still assume different windings orders though.

But why direct3d use left-handed transformation system? OpenGL use right-handed system but convert it to left-handed in normalized-device-coordinate.

Direct3D doesn't force you to use either convention. You can choose to use LH or RH.

 

The D3D9 fixed-function pipeline did use LH for some strange reason, but since then you've been able to choose.


Edited by Hodgman, 23 February 2013 - 12:04 AM.


#5 sobeit   Members   -  Reputation: 433

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Posted 23 February 2013 - 12:07 AM

 

i think every DCC like max, maya, modo, houdini, xsi, etc are all right handed. can't remember ever using one that was left handed. they may still assume different windings orders though.

But why direct3d use left-handed transformation system? OpenGL use right-handed system but convert it to left-handed in normalized-device-coordinate.

Direct3D doesn't force you to use either convention. You can choose to use LH or RH.

 

The D3D9 fixed-function pipeline did use LH for some strange reason, but since then you've been able to choose.

Oh, I see. in modern graphic programming, you basically do transformation in shader, so that's on your decision. Thanks.






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