Trying to accurately simulate LED lighting and a lense

[cash68]

Hi, industrial designer here.  I am working on a project that has a circuit board enclosed in a clear acrylic lens.  The issue we are having is that the LEDs don't diffuse very much, leaving us with hot spots in the center, and uneven illumination of the decal we will be placing on top.  We tried working with the decal supplier, and they were able to add a diffusion layer which helped a lot, but then the light was too dim.

So, here is the plan:

Simulate what we have currently, in keyshot, using reference photos.   These are the LEDs were are using:

https://www.digikey.com/product-detail/en/kingbright/AA3528SES-J4/754-1571-1-ND/2704776

I tried entering some of this data in Keyshot, I am using a basic 'spotlight' since that lets you adjust the viewing angle, but kind of lost on the rest of it.  Keyshot wants lumens, but the digikey has Microcandela.  I found a convertor online, but it also asks for the angle, so I'm not sure this is correct:

https://www.rapidtables.com/calc/light/mcd-to-lumen-calculator.html

Once I can achieve a rendering similar to real life, I will then CAD model some variations in the lens itself to try to diffuse the light more.   I have googled and come up with the refractory index of acrylic being 1.58, which I can enter into keyshot.  I'm also using the acrylic material from Keyshot, but changed the refractory index to 1.58 from 1.49.

So far this isn't even close to real life; the light looks white even though IRL it looks red.  It's also not scattering enough on the lens.  Help?

[DMerz III]

Have you tried just using an emission shader instead of spotlight?

Spotlight/Area lights are more for 'lighting' other objects. Where as emissive shader might be prone to preserving the hot color of light you're looking for. Not sure if this will solve your issue, but that's where I would start.

[TGS808]

This may (or may not) be of assistance.

https://www.keyshot.com/forum/index.php?topic=21022.msg89449#msg89449

[designgestalt]

hi there,
I would agree with what Mr. Merz the third said: an emissive would have been my first choice here. I would assume, that you have more control over the material tha the spotlight. It also gives you the possibility to mask the material with a color gradient, which would give you that uneven appearance. the colors alway "bleed" out, when you crank them up higher so you need to go for a much darker tone to achieve your final color, if you need that much power in your light.
my second choice would be a point light.
cheers
designgestalt

[mattjgerard]

The tip that worked for me is similar to the above, duplicate the geometry that you are using for the "light" and assign one the emissive to control the visual of the led and assign the other an area light, spotlight or point light to control casting light. Won't ever be able to use one light and get both the visual of the LED and the casting of the light correct. Much more flexible, and works for stuff like this-

[cash68]

Emissive doesn't have a viewable angle tho.  The LED specs say the viewing angle is 120 degrees, emissives are 360 degrees from what I understand, which would skew the results and not help me achieve diffusion.

[cash68]

Here's emissive, which..... looks a lot worse.

[mattjgerard]

Can we see some reference images of what you are trying to achieve? I've given up partially on getting physcially accurate results by just punching in numbers with LED lighting in KS. Just doesn't happen. I deal with light pipes, fiber optics and LED's behind cloudy plastics regularly. There is not really a "formula" that will work every time. The settings that will make red and green LED's look good do not work with Blue, that sort of thing. I've gone to LED chip manufacturers and downloaded the .ies files and tried to use those. Nope, its an art, lots of putzing with material settings, light settings and etc to get the look you are going for, and at the end it doesn't matter the numbers you use, its if it looks right. Frustrating, but that is the way it was with other unnamed render engines as well that I've used. I would love to just punch numbers in and have it work, but for some reason I can't get that workflow to work.

Anyway, if you can share some of the data, other magicians here can play with it and help make suggestions for your particular piece. This one here caused me much pain and anguish trying to figure out, but Dries here on the forum gave me some tips and pointed me to tone mapping which helped the propagation of the color through the cloudy plastic. Its a post production trick, and I was irritated that KS wouldn't work the way I wanted it to, I was hoping to not have to use Photoshop to achieve the look I wanted, but had to.

[DMerz III]

This may (or may not) be of assistance.

https://www.keyshot.com/forum/index.php?topic=21022.msg89449#msg89449

The solution is here, my man. Read this. BDesign (Eric) lays it out so well. Follow what he does, and you'll get what you're looking for, an LED appearance (hot color that doesn't desaturate) and light casting (which illuminates the area around it in colored light).

[mattjgerard]

Hahaha, that's funny, I was just looking for that post, and you beat me to it. That was one b#$tch of a project, and Eric really helped me out. Pretty much the rest of my work has been based on this way of working, so its pretty solid. I'm creating a folder of links to these gems of posts so I can go back and reference them.


Thanks for digging that up David, hope this helps the OP.

[cash68]

Sure, here's a reference image:

You can see the hot spots pretty clearly here.  I'm trying to match this in keyshot, and THEN make modifications to the B-side of the lens to see which approach has the most light diffusion.

[cash68]

How would I share my keyshot file?   Or cad data?

[cash68]

I tried following that link, the issue is a lot of those settings are no longer available in Keyshot 8.  There is not even a point light diffuse material available anymore.   Here's what I could achieve as close as possible to those directions (foreground) with the modified 120 deg spotlights in the background.

[mattjgerard]

CAD file would be great, if you can supply it. That way we are all playing on the same playground

[cash68]

https://grabcad.com/library/warning-light-diffusion-1

Try this, I have a BIP and a .stp

The bottom of the circular elements are LIGHTLY textured, which is in the BIP