IES size and shape?

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IES size and shape?

Postby Sheiken » Thu Jan 01, 2015 8:35 pm

Sheiken Thu Jan 01, 2015 8:35 pm
Hi,
I just started learning Octane today... after years with Maxwell.
I am a bit surprised abou the way IES emitters work. The power inceses when I scale out the plane. When I make the same plane a cube the power decreases. I suppose that is a bug...
The manual talks about spherical mapping with ies emitters, which we do not have in SU. I assume the plugin handles that, but what should I apply the material to (for accurate results)?

How accurete is Octane with IES & power etc? Can it be used for lighting simulations?
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Re: IES size and shape?

Postby Lewis » Fri Jan 02, 2015 12:21 pm

Lewis Fri Jan 02, 2015 12:21 pm
Not sure how is in Sketchup (but i suppose it won't be much different than other app plugins) but i dont' find it very accurate. I work with IES lights very much on my daily work (light projects/simulations) and IES in Octane work weird and it's not really acurate as tha tit reads Lumens/Lux values. In Octane it's very dependant on scale/size sicne Octane always uses "geometry" lights and doesn't really use Lumens from IES files. so yu can use it to get "nice" effect but don't think it as definite rela world value/intensity.

I also miss IES WEB/Shape in OpenGL. It's really hard to aim/use asymetric IES files when they look like flat plane/geometry

cheers
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Re: IES size and shape?

Postby Sheiken » Fri Jan 02, 2015 5:59 pm

Sheiken Fri Jan 02, 2015 5:59 pm
It is a shame if Octane can not be used for simulation of light. Maybe something that could be possible in the futute?
Having Efficassy and W settings is rather missleadind if the actual Lumens are dependant on the size of the emitter...

Well, I can use Maxell for simulations, but in practise Maxwell is to slow for interior scenes with many IES lights, and you can only observe the result thru a camera, so there is no way of knowing how much light the surfases are actually getting...

Maxwell uses geometry for IES lights, and they are not dependant on the size of the object. So, I am sure Otoy can also do it (even 80% accurate would be great).

Lewis, what do you use as a toll for light simulations?
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Re: IES size and shape?

Postby Lewis » Fri Jan 02, 2015 6:27 pm

Lewis Fri Jan 02, 2015 6:27 pm
Sheiken wrote:Lewis, what do you use as a toll for light simulations?


Dialux for exact Light calculations to se ehow much lux i have by ISO standard on what part of room/wall/desk....and then aproximate instensity with LightWave Photometric Light as close as possible to real world (since LW also don't read Lumens from IES files and it also depends on ColorSpace you are working in but I'm workign with many Luminaires Manufacturers so i often get real lamp samples for testing on site and the i can see/compare how it works/looks in real world and check with Luxmeter how intensive it is and then do it in LightWave native render engine by "eyeballing" to get close as possible. For some manufacturers (like Philips, Schreder, Thorn, Osram, Bega, Zumtobel..... which i used extensive during last 7-8 years i've managed to get some data/numbers which type of light needs whcih multiplyer for LW lights to get close to Dialux but so far I've not yet managed to use those logic in Octane render engine since it works completely different and as i said size of luminaire/polygon affects lightign too much to be taken as accurate).

Also I find Octane rendertimes suffer highly when usign lot of Lights. I've recently had scene with abotu 70 IES lights and dozen of COVE lights (various sahapes) and it takes eternity to render it clean (tied PT and PMC, AO was out of question for that scene due bad quality) and adjustind intensities is very hard/problematic since IPR don't show real intensity instantly but it takes quite some time untill it reaches full power and constant tweakign light sampling rate to see soem before ther is hard job (way to omany clicks/steps).

So i can't imagine usign Octane on heavy light scenes what i had in Lightwave during years, I had scenes with 5000+ IES lights and on my dayjob (Decorative/Street/Bridge Light simulations) i use 500+ light on daily basis for mid sized projects.

So unless they make a better way of OpenGl IES representation (grated this might be plugin specific but not sur eI've seen it any bette rin other softwar eplugin versions?) and some Light Lumens/reading option to be fully intensive as in real workd and instantly visible at IPR instantly as it starts i don't see Octane as viable option for such Light calculations/simulations.

Sorry if that dissapoints you but that's my findigs in last 6 months of using Octane for various tasks/projects.
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Re: IES size and shape?

Postby roy_orengo » Thu May 07, 2020 9:40 am

roy_orengo Thu May 07, 2020 9:40 am
Hello,
some Octane developer could explain this relationship? I think is very important to right understanding lights in Octane to use correctly it,
thanks,
Roy
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Re: IES size and shape?

Postby bepeg4d » Fri May 08, 2020 5:42 am

bepeg4d Fri May 08, 2020 5:42 am
Hi Roy,
you have reopened a very old discussion...what is exactly unclear about lights in Octane?
ciao Beppe
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