Re: 3d rotation question

[Keith W. <kw...@cs...>]

Roger Holmes wrote:

>
> On Monday, June 21, 2004, at 03:40  pm, Keith Wiley wrote:
>
>>
>> I can't figure out how to take the present orientation (a quaternion 
>> of course) and remove the vertical component of this orientation to 
>> flatten it to 0 without affecting the horizontal orientation (so the 
>> body is still looking along the same vertical azimuthal equator of 
>> the world but at 0 degree altitude).  How do I do this?
>>
>>
>
>
> Quesa's camera objects have a placement which has a camera position, a 
> point of interest
> and an up vector. If you set the Y value of the point of interest to 
> the same Y value of the
> camera position this should give you what you want. You might also 
> want to set the up vector
> to (0,1,0).

Thanks.  I might use that.  I was able to get the same effect by getting the presention orientation, zeroing the x and z parameters, and then orienting to the altered orientation, so w and y are left alone and x and z are zapped.  But points of interest are specifically made for these kinds of goals.  Perhaps I'll use that instead.

________________________________________________________________________
Keith Wiley                                kw...@cs...
http://www.unm.edu/~keithw                 http://www.mp3.com/KeithWiley

"Yet mark his perfect self-contentment, and hence learn his lesson,
that to be self-contented is to be vile and ignorant, and that to
aspire is better than to be blindly and impotently happy."
                                           --  Edwin A. Abbott, Flatland
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