A new light: the focused emitter

[Micha_cg]

Hi,

I'm working on my train interior scenes like this one, there a long thin emitter is placed on the edge of the luggage rack:

http://www.mobility.siemens.com/mobi...taet-large.jpg

and my problem was, that the light is focused to the ceiling. Yesterday I got an idea and created an emitter based on an angular blend material. At 1.05.29 this material cause crashes, but at the 1.5 beta it works. The lighting from the emitter can be focused and so I get my focused linear light.

Attached a Rhgino 5 file with the materials. A second material got an extra emitter layer that is angle independent so that the emitter is from all sides visible.

Ciao,
Micha

[renee81]

Great trick Micha !

[ledisnomad]

Sounds like a cool idea... but I don't get it. Micha, would you mind explaining it a bit more? I understand what you did, but I don't understand why. Wouldn't a long, rectangular light, rotated to point in the direction you want, do the same thing? Or a standard emissive material on a plan also pointing the direction you want? What am I missing? I'd like to know more to learn more about your material and how you're using it.

[Micha_cg]

The advantage is, that the light can be focused. A standard emitter material is sending light in all direction, in the example the whole "ceiling" would be homogeneous lighted.

[ledisnomad]

Just gave it a try and that's a pretty cool trick! Thanks for the trick and thanks for the additional explanation.

[kostenurka]

Very useful, thanks!

I suspect your problem is due to the closest distance between the emiter and the ceiling? In the reality this kind of light rather indicates only..
Dangerous place for the light by the way, I think it will be protected from the top anyway otherwise suitcases will not forgive it

Thanks for sharing!

[Micha_cg]

Today I played with the material again and here an interior with hundred emitter spots instead full raytraced spot lights.

[fooprobe]

super useful - great tip!

[Micha]

Could be nice if for emitter materials there would be an option to direct control the light distribution. Today I installed 48 focused emitters instead spot lights at an interior - works perfect. So I saved a lot of spotlights and calculation power for raytracing. Why not implement it as a feature?

[BIALOSKY_PARTNERS]

how does this affect rendertime/quality? I've always been under the impression that a emmissive material was very taxing when trying to use as the sole way to light a scene and that the quality was much more noisy. Have I been mistaken all these years?

[Micha]

Small emitters with a high intensity are difficult to sample for the random sampling of the GI calculation, that's right. But for example if you have a well lighted interior and like to add 48 wall lamps with focused light for a nice local light effect on the wall than you would need 96 raytraced spot lights (one up, one down). This would bring down the calculation time. Emitters are like simple objects and doesn't need more calculation time.
Attached an example how my focused emitters are working behind the wall lamp shape (I can't show the project rendering). In my case I render a train interior and the IM sampling is set at 150 subdivs, the focused emitters are well sampled.

I wished I could focus rectangle lights, that would help a lot too. Most I prefer rectangle lights and the option "store with IM". This keeps the render times low too.

[fpedrogo]

Hi Micha
In V-Ray for Rhino 3.0 we will have a directional option for the rectangular light and Probabilistic light. With the directional option you will be able to reduce focused the light and with probabilistic light you will be able to reduce the shadows ray calculation.

[Micha]

Great news.