Re: rotation in 3D

Steven wrote:
"I.N. Galidakis" <morpheus@xxxxxxxxxxxx> wrote in message
news:1207844007.909004@xxxxxxxxxxx
Steven wrote:

I want to rotate an object in 3d space with orthonormal axes x, y
and z. Target orientation is defined by orthogonal vectors x' and
y'. I have to rotate around x, y and z, respectively. (application
is POV-ray)
How do I do this?

You are trying to do it the hard way. POV-ray uses the orthonormal
axes <x,y,z>,
with x > 0 being to your right, y > 0 being up and z > 0 being
towards your
computer screen.

In addition, POV-ray has a macro for "camera". Here it is:

camera {
location <1.5, 1.5, -1.5>
look_at 0
angle 60
}

Instead of rotating the axes, successively change the camera
coordinates so that
the camera traverses the path of a circle normal to the axis you
want to rotate.

Rotating the camera on a circle around the y-axis for example (and
looking at
some fixed location like 0 above), is equivalent to rotating around
the y-axis.

I will let you figure out the circle equation for the camera rotation
(which is
very easy) as an exercise.

Once you figure out the equation, you only need plug-in the x and y
values in
the camera's "location", above.


This only works if there is only 1 object to rotate.

Well, your original question asked for one object:

I want to rotate an object in 3d space with orthonormal axes x, y
and z.

My scene has a
few dozens of objects, each with its own rotation, along a spline
path. AAMOF the rotation should follow the spline's curvature.

I don't understand what you mean by "along a spline path", but did you try the
macro "rotate"?

Thanks for your thoughts anyway,

You are welcome,

Steven
--
I.N. Galidakis

.

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