Alain Martel <kua### [at] videotronca> wrote:
> Start by creating your shapes around the Y axis if possible.
>
> Try using max_extent(Object) and min_extent(Object) like this :
>
> #declare Centre = (max_extent(Object) + min_extent(Object) ) / 2;
> //This will find the opposing corners of the bounding box, then find
> //their average. That average value is the centre of your object.
>
> #declare Object = object{Object translate -Centre rotate Some_Rotation
> translate Centre}
> //This translate your object by minus the found value, apply your
> //rotation, then translate your object back to it's original location.


This is mathematically correct and in my opinion the best/simplest solution if
it works properly *but* might not produce the desired result artistically for
each object. For example, picture a ballerina spinning with one arm
outstretched. Her average center of rotation would probably be somewhere near
her shoulder, so a more complex formula (or artistic judgment) is sometimes
necessary. For these abstract shapes perhaps that will suffice, or perhaps it
will look awkward. I would certainly try this method first and see how it looks.
It will probably look great. I'm very curious to see because this is an
interesting artistic question. If it doesn't look right then here's another
possibility that I would try: Place each object in turn inside a vertical
cylinder centered on the y axis. Use highly contrasting colors so you can easily
see where the object extends outside the cylinder. You can also make the
cylinder partially transparent. Adjust the radius of the cylinder and the x and
z positions of the blob object until it "feels right."

I'm looking forward to seeing where this leads!

Kind regards,
Dave Blandston

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