On 12/14/2013 08:55 PM, Alain wrote:

>> http://wiki.povray.org/content/Reference:Union#Split_Union
>>
>> OK ... narrative says it's used with photons, but made a typo and
>> accidentally enabled on a tile floor (many tiles and grout) but I wasn't
>> using photons. The object count went down like expected, but render time
>> slowed to a crawl ... walked away from computer, and the usual 3 minute
>> render had only managed to get almost through the first row. Like I said
>> a mistake, and can't off the top of my head think of any use of
>> split_union /without/ photons ... could it be that split_union should
>> first check for photon usage then ignore the "on" setting if photons
>> aren't used?
>
> Normaly, unions are split into the individual component. It improve
> bounding, making the scene render much faster. Each component have it's
> own bounding box.
>
> With split_union off, you are forced to evaluate the whole union, and
> all of it's elements, for every ray that enter it's bounding box. You no
> loner have the individual bounding boxes, bot only one large one.
> You get something similar when you use merge or apply a manual bounding
> on an union.

Yes I understand the premise, but that really didn't answer the question 
I posed (I don't think) ... is (or should) split_union be exclusive to 
photon usage. That /is/ the only usage the doc passage cites.

Post a reply to this message