That's far simpler and more elegant. I must really be having an off-day 
:s

Thanks

"Alain" <aze### [at] qwertyorg> wrote in message 
news:4b9a97c1$1@news.povray.org:


> > Hi all.
> >
> > I've been staring at this for 20 minutes and I'm obviously missing
> > something really obvious. Would one of you be kind enough to point out
> > my mistake?
> >
> > I want to stand a box on one corner (so the lowest corner is at the
> > origin) and rotate it about the y axis (which should pass directly
> > through the upper/lower corners).
> >
> > box {-.5,.5
> > texture{BoxTexture}
> > rotate 45*z
> > rotate 45*x
> > translate y*pow(3,.5)/2
> > rotate -y*(30+clock*360)
> > }
> >
> > I also have a plane {y,0} with a reflective texture. The tip of the
> > reflection and box come _very_ close but do not quite touch (more than
> > an AA artifact).
> >
> > When the cube is rotated, the top/bottom corners describe small circles
> > horizontally - Which leads me to conclude I haven't rotated the cube
> > correctly - but 45/45 seems intuitively correct?
> >
> > What am I doing wrong when orientating the box?
> >
> > Sorry to have to ask such a simple question - I've just been staring at
> > it too long
> >
> > Many thanks in advance
> >
>
> Start your box as:
> box{0,1...}
>
> That way, you start with a corner exactly at the origin, eliminating any
> need to translate it. Without any translation, the lower corner will
> exactly touch your plane at 0,y and the y rotation will be around it
> without any chance of it moving.
>
> Sometimes, as in this particuliar case, creating the object around the
> origin is not the best way. Creating it with a specific point at the
> origin is the best way.
>
> Then, you rotate it as Tim explaned.
>
> For any object destined to rest on another, like on a floor, if's often
> beter to create it with it's base at 0*y. It's beter to create a door
> with one of it's edge at 0*x and 0*z and it's base slightly raised:
> 0.1*y for example.
>
>
>
> Alain

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