[Bf-committers] Default for Raytracer Instancing

[Matt Ebb]

On Mon, Jan 31, 2011 at 7:45 AM, Bassam Kurdali
<bkurdali at freefactory.org> wrote:
> I have noticed this too, turning on instancing, in scenes with lots of
> instances, sometime leads to longer render times. In the past it has
> been faster, too, so I don't know what's going on, or why it should have
> these results.

It's plausible that enabling it can lead to longer render times, since
it has to do more work (extra transformations) when intersecting rays.
Though I imagine it could vary from scene to scene - scenes without
any actual instances would be slower, but perhaps some scenes with
instances could be faster too (if it's always intersecting the same
object, it may be better for the cache?). The main reason for using
instances is to lower memory usage anyway - some scenes you just can't
render without it.

I'd be in favour of enabling it by default, but perhaps it could be a
bit smarter - i.e. if instancing is turned on, but no instances are
actually found during the render's geometry pre-processing, then it
could just disable instancing internally for that render. Not sure if
the code's organised in a way that would make that easy, but it makes
sense to me.

cheers

Matt