[Bf-cycles] ray depth

David Fenner d4vidfenner at gmail.com
Mon Oct 6 20:50:55 CEST 2014

Hmm I don't understand what you mean brecht... I never said anything about
wanting no global bounces at all, in the first mail I explained that
usually some lights (like environment) need GI but many auxiliary lights
used to "paint" polygons don't. For example, think of a scene that has 2
lights with GI, and 8 lights (rims, face aux, eye aux, some torch,
whatever) don't need GI, and in fact GI works worse visually. In this scene
there would be no gain at all by making these 8 lights not bounce, but
since they don't bounce, can't these rays not be calculated to make it

Please check first mail, the idea is to make it easier to make some lights
not bounce for artistic control and that this also helps to optimize speed,
since they don't bounce... I don't even know if its possible, but I do
believe that a scene with 8 lights bouncing should render slower than one
with 1 light bouncing (of 8), or this is not possible with pathtracers??

2014-10-06 13:49 GMT-04:00 Brecht Van Lommel <brechtvanlommel at pandora.be>:

> Well yes, it would be nice if Cycles could automatically detect when it
> can set global bounces to 0, but you're not gaining any new capabilities
> this way. I imagine that if you want no light bounces at all, then you
> would have probably just set global bounces to 0, rather than going through
> the trouble of changing all lamps, emissive surfaces, volumes, ambient
> occlusion, the world shader, and whatever else in the scene might be
> emitting light.
> There are various optimizations possible here, but this specific case
> doesn't seem all that helpful for a production scene?
> On Mon, Oct 6, 2014 at 1:52 PM, Greg Zaal <gregzzmail at gmail.com> wrote:
> > Done some tests too and David is right.
> >
> > 128 bounces, 5:14 - http://i.imgur.com/XFdhp9l.png
> > 128 bounces with Ray Depth trick, 5:11 - http://i.imgur.com/p8kL5ki.png
> > 0 bounces, 4:10 - http://i.imgur.com/xQdrSQD.png
> >
> > Nodes used for one of the lamps: http://i.imgur.com/MBsi7hh.png (also
> tried
> > http://i.imgur.com/htdCsxi.png - made no difference)
> > Blend file: http://pasteall.org/blend/31928
> >
> > Cheers,
> > Greg
> >
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> > Bf-cycles at blender.org
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> >
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