> 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.
>

Been the only place where it's mentioned don't mean that it can *only* 
apply when photons are used. split_union is an object modifier, just 
like no_image, no_shadow, no_reflection, no_radiosity or hollow that can 
all take an optional on/off parameter.

The only difference been that split_union default to off while the above 
modifiers default to on by their sole presence and off when absent.

Post a reply to this message