[Bf-committers] Default for Raytracer Instancing

[Daniel Salazar - 3Developer.com]

Matt instancing speeds up in orders of magnitude when a scene uses instances

Daniel Salazar
www.3developer.com



2011/1/30 Matt Ebb <matt at mke3.net>:
> 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
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