hi,

William F Pokorny <ano### [at] anonymousorg> wrote:
> ...
> The still image looks cool! :-)

thank you.  had wanted the podium flanked by a couple of bay-trees (or
cypresses) in planters, like the "for hire" type seen at events, but could not
find anything "ready made".  there are other .. niggles.  btw, forgot to say,
the "checkered plane" was added because of the recent "RSOCP" revival.  :-)


@Bald Eagle

thanks.  quick paper and pen shows it works for axis-aligned cubes, will need to
write some code to test more arbitrary sets of points.


@Cousin Ricky

I guess I don't really need radius/diameter of sphere/cylinder?  I think[1] just
the points, as BE suggests, should do.

[1] fwiw.


@Alain

making shapes near/around Y will be difficult/not possible in some cases.  I'm
still experimenting with different layouts when using character values to create
"random" points, but only one of those (so far) could be written that way.


@Dave Blandston

"mathematically correct" vs "artistic intention" - good point.  thanks for the
cylinder suggestion, yesterday I wrote some code using a wireframe box + three
axes to make a crosshair to aid positioning (but that's a crutch at best because
it means .. _fiddling_).  and thanks for the interest, I too am keen "to seeing
where this leads" :-).


re the bounding discussion.  reading this with interest.  below are the unscaled
sizes of the three shapes in the image.  first POV-Ray "max_extent() -
min_extent()" values, then the 'Bounder'[2] macro's take on the objects; the
second set of sizes is the same shapes but with rotations applied (ie oriented
as in the image).  much "air" in those bboxes.

[2] using default '<50,50,50>' resolution.  (still took about an hour to parse)

-----[ no .Rotate
gold   <6.777,7.425,6.777>
silver <10.308,8.902,10.907>
bronze <6.580,5.617,5.396>
----------[Bounder info]------------------------------------------------
       BB aligned dimensions: <6.776587, 7.424744, 6.776587>
     BB optimised dimensions: <2.518731, 5.263363, 2.238872>

       BB aligned dimensions: <10.308336, 8.902399, 10.907174>
     BB optimised dimensions: <8.146588, 4.801294, 7.204739>

       BB aligned dimensions: <6.580112, 5.616580, 5.396318>
     BB optimised dimensions: <3.680063, 3.737724, 3.457641>

-----[ .Rotate
gold   <8.300,7.425,8.300>
silver <10.907,10.308,8.902>
bronze <9.945,8.471,8.292>
----------[Bounder info]------------------------------------------------
       BB aligned dimensions: <8.299590, 7.424744, 8.299590>
     BB optimised dimensions: <2.279887, 5.263363, 2.339884>

       BB aligned dimensions: <10.907174, 10.308336, 8.902399>
     BB optimised dimensions: <7.204739, 8.146588, 4.801294>

       BB aligned dimensions: <9.945232, 8.470688, 8.292479>
     BB optimised dimensions: <4.582411, 4.035564, 3.037245>


regards, jr.

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"jr" <cre### [at] gmailcom> wrote:

> @Bald Eagle
>
> thanks.  quick paper and pen shows it works for axis-aligned cubes, will need to
> write some code to test more arbitrary sets of points.

As far as I can tell, this approach ought to work great with any arbitrary set
of sizeless points.

As Dave points out, once you start to add some volume, things get offset a bit.

If all of the points on the ballerina's surface were used to create a positional
average, it ought to work just as well, so maybe a trace() approach would be
simplest.

I'm sure there might be a way to do it where the point-center is found, and then
the blob sphere center point vectors are weighted according to the radii.
Probably hard to parse and understand that, but I think a diagram would show
what I mean...

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Le 2022-02-01 à 01:34, Dave Blandston a écrit :

> 
> 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
> 

In the case that you mention, the solution would be to add some offset 
when translating :

#declare Offset = Artistic_Adjustment_Value;

#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+Offset rotate 
Some_Rotation translate Centre-Offset}
// This translate your object by minus the found value adjusted by
// the artistic offset, apply your rotation, then translate your
// object back to it's original location.

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