Help - how to reproduce emergency/neon colors ? (not neon lights)

dream-weaver

Does anyone know how to properly replicate emergency/neon colors/surfaces like on emergency cars?
Is there a shader available?

For example here the neon yellow

Gordig

The proper way to do something like this would be to make the material retro-reflective, and I'm not sure what setting would do that in Iray.

Matt_Castle

Moderate to high backscattering strength and roughness approximates retroreflective materials; I used the technique in this recent render to alter the default materials on the Road Work Outfit - mostly by moving the metallicity map to be used for the backscatter strength.

This is what lets it catch the light rather differently to the other parts of the jacket around it (more obvious in the shading on the left side of the image).

Charlie Judge

A hard surface neon shader:  https://www.daz3d.com/iray-hard-surface-shaders-volume-four-brights-and-neons

dream-weaver

Matt_Castle said:

Moderate to high backscattering strength and roughness approximates retroreflective materials; I used the technique in this recent render to alter the default materials on the Road Work Outfit - mostly by moving the metallicity map to be used for the backscatter strength.

This is what lets it catch the light rather differently to the other parts of the jacket around it (more obvious in the shading on the left side of the image).

Do you mind showing a screenshot of your surface settings for the neon on that vest?

I was previously experimenting with giving the surface a slight emission value to immitate the signal color effect. But I wasn't really happy with the results.

dream-weaver

Here is what I have come up so far on my own amateur skills. Example and my settings.

The caliper in the light seems somewhat ok to replicate neon orange. But the one in shadow would very likely be brighter in reality with proper neon color painting.

 

Matt_Castle

As far as the retroreflective properties, this is what I had.

As far as fluorescence though, I'm not yet sure how to replicate that well, so I didn't try. Adding emission isn't really accurate, because fluorescence doesn't *make* light, it takes one wavelength of light and then emits it at a lower frequency (usually taking UV or blue light and emitting it as red, yellow or green. Fluorescent blue is rare, as blue photons would have to be activated by UV, which is a small portion of a typical light spectrum). There's no proper function for that in Iray Uber, so I think I would actually need to make a custom shader block that could take intensity from the blue channels and add it to the red or green channels... and I'm not even sure if swapping light between channels is possible.

murgatroyd314

Matt_Castle said:

Fluorescent blue is rare, as blue photons would have to be activated by UV, which is a small portion of a typical light spectrum).

It's more common than you think. Most bright whites (e.g. paper and clothing) have a significant fluorescent blue component. 

Matt_Castle

Component, yes, but it's rare to see something that is *solely* fluorescent blue; the effect is weaker and usually it gets overpowered by the rest of the spectrum. (Almost all cases I've seen of exclusively blue fluorescence have had to be done in a dark environment with a specifically UV source).

The fact it needs to be activated by UV would make it a problem when rendering in RGB colour if it were more significant, but if we accept that limitation long wave length (red, yellow or green) fluorescence could theoretically be simulated based off the blue channel. But that would depend a lot on the inner workings of the renderer.