Am 16.03.2015 um 22:06 schrieb bublible:
> clipka <ano### [at] anonymousorg> wrote:
>> Am 16.03.2015 um 20:39 schrieb bublible:
>>> Is there a way to find out/obtain/get object's "rotation matrix" so it can be
>>> applied to another object?
>>
>> Nope, sorry. You'd need to modify POV-Ray's source code for that stunt.
>> (And, knowing that you're wrestling with LDD-to-POVRay, that won't get
>> you anywhere either because the tool is designed in such a way that
>> scenes won't render with an unofficial version of POV-Ray. Did I mention
>> before that the tool sucks big time?)
>
> yea you did mention it but it didn't help me much in solving my problem so I did
> not care to reply, sorry :D

Even if you had replied, I'd have happily taken the opportunity to again 
point out what I think of the LDD-to-POVRay tool ;)

> anyway, there have to be some way as I have here one script dealing with
> automatic rotation of background (ehm, actually a box functioning as background)
> that expands and face directly to camera nevermind cameras position which is
> basically what I want but I want just one axis to be corresponding to the camera
> axis in oposite angle as my polygon is rotate<0,0,0> and I want it turns to
> directly to camera but only on its y axis (I got gradient polygon functioning as
> a base plane and I need its gradient would always go from camera to the distance
> far away independently of LDD/camera rotation)

If you can get that far from whatever parameters there are floating 
around in the scene, then here's what I'd do:

(1) Transform a unit vector (x or z, depending on the original 
orientation of the model) according to the rotation matrix, using the 
vtransform() function.

(2) Take the resulting vector, and multiply it by <1,0,1>.

(3) If needed, normalize the resulting vector using vnormalize().

=> Voila, you should now have rotated the original vector around the y axis.

If what you need is a rotation rather than a rotated vector, continue as 
follows:

(4) Compute the cosine of the angle between the (normalized) rotated 
vector and the original vector by computing the dot product, using the 
dot() function.

(5) From the cosine of the angle, compute the angle in radians using the 
acos() function.

(6) If needed, compute the angle in degrees by multiplying with 180/pi.

(7) If you find that the rotation doesn't fit, try inverting the sign.

I hope this helps.

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