I want to create a spiral lamp element sort of like a CFL. Which will 
render faster, a series of point lights along the curve, or making the 
object emit light? Thanks!

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On 1/7/2016 6:18 AM, Mike Horvath wrote:
> I want to create a spiral lamp element sort of like a CFL. Which will
> render faster, a series of point lights along the curve, or making the
> object emit light? Thanks!


Or an area light with a "Looks_like" a spiral lamp element. That would 
be faster.

The in built help works with Looks_like. :)


-- 

Regards
     Stephen

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Mike Horvath <mik### [at] gmailcom> wrote:
> I want to create a spiral lamp element sort of like a CFL. Which will
> render faster, a series of point lights along the curve, or making the
> object emit light? Thanks!

That depends on whether you're using radiosity anyway, how close the lamp is to
the visible portions of the scene, and whether it is the main light source.

Generally, scenes illuminated by comparatively small emissive objects require
exceptionally "expensive" radiosity settings. The "importance" mechanism can be
used to counter this to some degree, but not completely.


That said, using an excessive number of point light sources can also slow down a
render tremendously. You might instead want to think about using an arrangement
of 1-dimensional area lights approximating the lamp's shape.

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On 1/7/2016 8:33 AM, clipka wrote:
> Mike Horvath <mik### [at] gmailcom> wrote:
>> I want to create a spiral lamp element sort of like a CFL. Which will
>> render faster, a series of point lights along the curve, or making the
>> object emit light? Thanks!
>
> That depends on whether you're using radiosity anyway, how close the lamp is to
> the visible portions of the scene, and whether it is the main light source.
>
> Generally, scenes illuminated by comparatively small emissive objects require
> exceptionally "expensive" radiosity settings. The "importance" mechanism can be
> used to counter this to some degree, but not completely.
>
>
> That said, using an excessive number of point light sources can also slow down a
> render tremendously. You might instead want to think about using an arrangement
> of 1-dimensional area lights approximating the lamp's shape.
>
>
>

So, area lights are cheaper than an equally sized array of point lights?


Mike

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Am 08.01.2016 um 00:46 schrieb Mike Horvath:

> So, area lights are cheaper than an equally sized array of point lights?

Yes, absolutely: With an array of point lights, POV-Ray needs to perform
shadow tests against every one of them every time. With an area light,
POV-Ray can choose to ignore some of them if it finds that their
neighbors are all shadowed or all unshadowed. It's kind of like
anti-aliasing.

You'll need to use the "adaptive N" keyword to enable this optimization,
where N governs how many of the sub-lights POV-Ray will always test:
POV-Ray will initially render only (2^N)+1 of the sub-lights in each
direction, then render the sub-lights halfway between those that gave
noticeably different results, and then in the same way "drill down" ever
further until it reaches the level of maximum resolution you specified
for the area_light.

Another way in which area lights can speed up rendering is that normally
they only affect shadow testing, while still behaving as a single point
light for diffuse and highlight computations. (If that is undesired, for
instance because the light source is very close to a surface, you can
use the "area_illumination on" keyword to make the area light affect
diffuse and highlights as well.)

And the third way in which you can benefit from area lights is the
"jitter" feature, which can reduce banding artefacts in soft shadows
without having to increase the number of sub-lights.

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