Am 02.08.2016 um 22:55 schrieb Bald Eagle:

>> However, the main factor is the careless use of `difference`. For
>> instance, a heat sink modeled as a union of a base and 11x11 = 121
>> individual "fingers" renders about 10 times as fast as a heat sink
>> modeled as a single block with 2x10 = 20 "grooves" cut into it.
>>
>> As a rule of thumb, avoid `difference` wherever possible.
> 
> Really???   My heatsinks are ALL primarily made with loops of differences.  I
> try to avoid them, after reading Mike Williams' page about holes, but they are
> convenient.   It must be something else slowing down that scene.

Sorry, I made the "main factor" statement above in error, based on the
factor 4 speedup for making the area lights adaptive. I hadn't measured
the speedup for eliminating the area lights classic entirely.

It turns out that the area lights account for a factor of about 40,
which is obviously more than the factor of 10 for the differences.

Still, avoiding differences does pay off -- and in contrast to avoiding
area lights it doesn't reduce the render quality.

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