Reflective Paint Question

[joelly3d]

What makes street line paint, worker vests and warning tape so highly reflective?

Here's an image example of what I mean: https://img.alicdn.com/imgextra/i3/3...400x400q90.jpg

Seems like it can be done with a high IOR, but there si probably more to it I am guessing. Has anyone tried to mimic this type of material?
Any thoughts appreciated!

[fixeighted]

I found this quite easily, though there are other techniques https://reflectivetape.info/how-is-r...cro-prismatic/

[joelly3d]

Yeah I ran into that. After thinking on it, I am thinking it may be possible to make a more accurate representation of it with a flakes material, with a huge amount of flakes.

[DaveKW]

How would you get the reflected ray to bounce back in the same direction as the incident ray?

[joelly3d]

Not sure it is possible with existing materials, could be an interesting thing to explore for a programmer to try out though. I'll just make a stupid high IOR material for now and move on. I don't have any R&D time on this job unfortunately. Can't get caught up in the weeds when i have a ton more big picture items to tackle! That documentation provided by fixeighted is pretty interesting though. Looks like a Siggraph paper waiting to be implemented!

[joconnell]

Someone in work has a retro reflective jacket and it looks like something's gone wrong in a render - i'd be inclined to use a falloff map and invert it so it's more reflective in the centre. See can you get a sample, wrap it around a cylinder so you get from 0 - 90 degrees and take a few photos of yourself shining a torchlight on it from front on to side on as ref.

[dgruwier]

My colleague Dan Andersen showed me a way to do a perfect retroreflective material in Maya (I'm sure the process is identical in Max):
Route the ray direction of a samplerInfo node into a multiplyDivide node with the blue channel set to -1000 (need to use the connection editor to make that connection for some reason), then pipe that into the bump map with Map Type set to screen space. That'll flatten the normals in the direction of the camera. Bump mult controls how strong the effect is.

I'm still not quite sure why it works, but there you go, that'll give you a very nice and clean retroreflective material.

[joelly3d]

That is pretty clever and I'll give it a whack! it'll be different in Max, but the concept is the same, I use Maya too, so I follow the logic.
Thanks DG!

[kosso_olli]

There was a challenge over at shader xyz for exactly that kind of thing: https://forum.shaders.xyz/d/2532-cha...roreflector/66
Some people gave details on how they've done it.

[DaveKW]

I can't for the life of me figure out how to apply any of that in Max.