[Bf-cycles] Distance Culling of Lamps?

Matthew Heimlich matt.heimlich at gmail.com
Tue Feb 3 22:22:46 CET 2015

This is already done to a certain extent by cycles automatically.
On Feb 3, 2015 4:19 PM, "Zauber Paracelsus" <zauber at gridmail.org> wrote:

> Would it be possible, through a new lamp setting, to support
> distance-based culling of lamps?  The basic idea is that lamps would not
> be sampled if they are far enough away from the area being sampled,
> thereby cutting down on rendering time.
> This can already be done to a degree by using nodes via the Ray Length
> output of the Light Path node, and I find that in complex scenes with
> numerous surfaces and several lamps over a large area, it can reduce
> rendering times by roughly half.
> However, there are two flaws with this approach:
> 1) Ray Length only measures the length of the current ray, meaning it
> could still be sampled despite being a greater distance away.
> 2) Ray Length is supplied after a bounce is calculated (I think),
> meaning it would not be fully sufficient to stop the lamp from being
> sampled.
> If distance culling for lamps is supported directly within blender,
> however, then it would perhaps unlock larger performance gains because
> it would stop the lamp from being sampled before any bounces are
> calculated.
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