Path: chuka.playstation.co.uk!scea!hobbes
From: jamin1@psu.edu (Jamin Frederick)
Newsgroups: scee.yaroze.programming.3d_graphics
Subject: Re: "center"
Date: Mon, 29 Jun 1998 21:31:41 GMT
Organization: SCEA News Server
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Ok, here's another problem.  How to make an object rotate around separate 
pivot points once it is loaded into memory.  For instance, if I load a rod 
object, and decide to push on one end, the pivot point is no longer in the 
center of the rod, but farther at the opposite edge.  The question is *how* to 
rotate the object now, since I don't want it to go around the old pivot point 
(the center), but around the new pivot point.  Is there a way to do this 
without having to alter the center of the object, which means changing every 
single polygon vertex??


Jamin

In article <6n90bb$51f1@scea>, jamin1@psu.edu (Jamin Frederick) wrote:
>I figured it out, "center" is the center of mass of the object, and rotation 
>is not done about this point, but always about the origin (0,0,0).  To make an 
>object rotate around its center, and if its "center" is offset, you have to 
>translate the whole object so that its center sits on (0,0,0).  Then rotation 
>will be correct (around the center) of the object.
>
>
>Jamin
>
>In article <35911bf4.80589781@news.scea.sony.com>, jamin1@psu.edu wrote:
>>        Could someone tell me the significance of the "center" coords
>>of .rsd files?  Is this center coord with respect to the object's own
>>coord system, and if so, why is it needed?  Is rotation and scaling
>>done about this "center" or the origin of the object's coord system?  
>>
>>Thanks,
>>
>>Jamin