On 1/30/22 15:48, Cousin Ricky wrote:
> On 2022-01-30 12:01 (-4), jr wrote:
>>
>> I had wanted to make an animation of the shapes rotating above the podium, but
>> they .. orbit.   because the bounding box "method" doesn't work too well, I need
>> to calculate the geometric centre (?) of a given 'blob'.  did some googling on
>> the subject but have only found 2D solutions so far.  help please.
> 
> I have a couple of suggestions.  If you know the surface radius of each
> component, you can create a union of spheres, and take the center of the
> union.  Function RE_fn_Blob_surface_radius() in roundedge.inc can
> calculate the surface radii.
>    <https://github.com/CousinRicky/POV-RoundEdge>
> 
> Alternatively, you can go brute force with trace() or inside(), and take
> the center of all the successful hits.  inside() would take longer than
> trace(), due to being volumetric, but it would allow you to compute a
> rough center of gravity, rather than just computing the center of the
> extents.

I'll toss a couple more ideas on the table.

You can still manually bound objects but you have to turn the automatic 
bounding strip off. -ur (IIRC). Not sure any advantage over the union of 
spheres idea.

The blob object is one of two objects supporting a potential pattern for 
itself. Further I think is uses effectively 'raw_wave' internally though 
it's not brought all the way out to an official keyword in v3,8/v4.0 as 
it is in povr. It should be you can sample actual blob internal values 
too though unsure if any better than trace/inside testing. The greatest 
inside value (most positive IIRC with blobs) won't necessarily be the 
center of mass depending on the shape and construction.

The still image looks cool! :-)

Bill P.

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