Hidden lighting

[Peter Milner]

Okay, so what's the best way to create hidden LED lighting without getting reflected light sources and millions of "fireflies"?

[Roy Hirshkowitz]

You might try modeling them with a hidden, rectangular, area light. Many of these LED strip lights are encased in a plastic diffusing tube for this very reason.

Make sure the light is facing the right direction.

[Peter Milner]

Most hidden LED strip light is now sold from a roll by the metre. This is the sort of stuff we use.

I've tried using a rectangular area light, but that gives me an unrealistic rectangular reflection.

I may have to resort to Photoshop to fake it.

[Roy Hirshkowitz]

Yep-- these sometimes do exhibit discreet reflections.  Does the hybrid engine do any better with these?

[Peter Milner]

I'll give it a whirl tomorrow.

[Jan Verzelen]

this s what i get when trying to simulate led strips. i used rectangular hidden and visible area lights with the path tracer.

[Roy Hirshkowitz]

It works pretty well for this-- where the surfaces are diffuse.  Peter's got a more reflective surface which probably would show reflections of the individual light sources in the roll.  It's an interesting problem (and an actual one faced by designers, not just simulators/renderers.)  LED lighting is more discretized and less diffuse than other forms of lighting.

[Jan Verzelen]

okay, but why should one try to draw each separate light source? As you mentioned before, most of the time these are behind a diffuse cover.

[Roy Hirshkowitz]

If they're behind a diffuser-- yep-- modeling the diffuser as a light source will get you most of the way there.  The type of lighting that a lot of folks are using, though, is these exposed 3M lighting strips.  They resemble Christmas lighting a little bit and may be difficult to simulate adequately.  We'll see.

[Sampdoria]

Hello Peter and Roy.

I use the Rectangular Area Light, in my case Im not creating the renders for light precision. I do end up however having to always play with light channels to my advantage and also separate Render Engines and overlay.