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I'm having trouble thinking through a transformation problem, and I'm
pretty sure this isn't too crazy of a problem.
The idea is that I have an object centered at the origin, let's say a
thin oval with the major and minor radii along the x and z axes, (so the
normal on the flat face is in y). I want to rotate this so the x and y
axes are pointing in the direction of two arbitrary (normalized and
perpendicular) vectors.
transforms.inc has the Point_At_Trans(newY) that will do half this
problem, but if I want to then rotate the x axis to align with another
vector, it will mess up the original translation.
The object can then be translated to be centered at a given point, but
that part is easy.
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CShake <cshake+pov### [at] gmail com> wrote:
> I'm having trouble thinking through a transformation problem, and I'm
> pretty sure this isn't too crazy of a problem.
> The idea is that I have an object centered at the origin, let's say a
> thin oval with the major and minor radii along the x and z axes, (so the
> normal on the flat face is in y). I want to rotate this so the x and y
> axes are pointing in the direction of two arbitrary (normalized and
> perpendicular) vectors.
Why rotate when you can shear? :)
transform { Shear_Trans(newX,VCross(newX,newZ),newZ) }
There. Shear_Trans is your friend, too :)
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> I'm having trouble thinking through a transformation problem, and I'm
> pretty sure this isn't too crazy of a problem.
> The idea is that I have an object centered at the origin, let's say a
> thin oval with the major and minor radii along the x and z axes, (so the
> normal on the flat face is in y). I want to rotate this so the x and y
> axes are pointing in the direction of two arbitrary (normalized and
> perpendicular) vectors.
>
> transforms.inc has the Point_At_Trans(newY) that will do half this
> problem, but if I want to then rotate the x axis to align with another
> vector, it will mess up the original translation.
>
> The object can then be translated to be centered at a given point, but
> that part is easy.
I think what you want is Shear_Trans.
As long as the vectors you supply are normal and perpendicular
the object just gets rotated. You can use VPerp_To_Plane to
get the third vector...
#include "transforms.inc"
#include "math.inc"
object {
Foo
Shear_Trans(Xvec,YVec,VPerp_To_Plane(Xvec,YVec))
}
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clipka wrote:
> Why rotate when you can shear? :)
>
> transform { Shear_Trans(newX,VCross(newX,newZ),newZ) }
>
> There. Shear_Trans is your friend, too :)
>
Thanks, that works perfectly. I knew there was something stupid simple
to use, but was afraid of all the Shear transforms because it always
makes me think of distortion.
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CShake nous illumina en ce 2009-03-11 23:23 -->
> clipka wrote:
>> Why rotate when you can shear? :)
>>
>> transform { Shear_Trans(newX,VCross(newX,newZ),newZ) }
>>
>> There. Shear_Trans is your friend, too :)
>>
>
> Thanks, that works perfectly. I knew there was something stupid simple
> to use, but was afraid of all the Shear transforms because it always
> makes me think of distortion.
It IS a distortion, as is any unevent scaling. It change the basic shape of the
object, but in a very controled way.
--
Alain
-------------------------------------------------
Q: If pro is opposite of con,then what is the opposite of progress?
A: Congress!
Men's restroom, House of Representatives, Washington , DC
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