[Bf-cycles] Efficient sampling of many lights

Marco G digitalbath86 at hotmail.com
Wed Jun 25 21:55:53 CEST 2014

I've seen this back in that forum and tought looked great indeed. Is there any downside about such approach? Because from what i can see it would be great to have. 
Many times in my scenes branched PT isn't beneficial, but with simple PT + many lights it gets impossible when dealing with tens of lamps. So if standard path tracing could be optimized for many lights scenarios with this technique, i really wish someone has the ability to add it  
I'd love to hear Cycles devs opinion. Regards 

> Date: Mon, 23 Jun 2014 16:34:16 -0700
> From: cessen at cessen.com
> To: bf-cycles at blender.org
> Subject: [Bf-cycles] Efficient sampling of many lights
> I had mentioned this to Brecht a while back, but since he won't be
> working on Cycles anymore I thought I'd drop a general note here.
> Currently Cycles either uniformly randomly chooses a single light to
> sample for each ray hit, or it samples all lights for each ray hit.
> The former significantly increases noise as you add more lights to a
> scene, and the latter significantly slows down rendering as you
> approach large numbers of lights.  As far as I know, this is a problem
> common to all path tracers.
> In the process of writing my own toy renderer, I came up with a method
> that significantly improves on this problem and can efficiently sample
> among many light sources.  I outline the technique in this post on
> ompf2, which includes some example before/after renders:
> http://ompf2.com/viewtopic.php?f=3&t=1938
> The technique is not thoroughly tested, as my renderer only supports
> limited light and material types.  And it surely needs more design and
> development work.  But it seems to work well, and especially for
> scenes with hundreds of lights or more it provides an enormous
> benefit.
> I don't currently have any plans for developing on Cycles, but I'm
> noting the technique here just in case anyone is interested in
> attempting to implement it in Cycles.
> --Nathan
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> Bf-cycles at blender.org
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