[andyjacobs]

Hi,

I have a project where I need to included a retroreflective material like this: http://bowiestie.files.wordpress.com/20 ... -5_001.jpg

I saw an old thread from V1 where someone attempted this, but didn't get anywhere. All I could find online was a reference to a index of refraction of 2.

Anyone have any ideas?

[tom]

I guess you may start with one of these.
http://resources.maxwellrender.com/sear ... v2=0&tipo=
http://resources.maxwellrender.com/sear ... v2=0&tipo=

[eric nixon]

He said retroreflective, not reflector.

here is a retroreflective attempt;



There are two geo's inner object is a rough shiny metal, OUTER OBJECT HAS SSS, low nd (1.15), high coef (90000), high POSITIVE assymetry (0.85)

[tom]

He said retroreflective, not reflector.

Am I missing something?
http://en.wikipedia.org/wiki/Retroreflector

[eric nixon]

Is wikipedia wrong

Well, maybe the correct term is not retroreflective.. But thats the effect he wants..

Anyway I forgive you

[tom]

Why do you think he doesn't mean retroreflective but something else?

[eric nixon]

I was thinking that sss with positive assymetry could give this effect;

Now I see that they are the same thing., you were right... but do you mean to say that a normal map can do it? I mean the SSS way seems to work?

[eric nixon]

I tried it with 2 geo's and a normal map, and no sss, it appears to work, but only with HDRI not emitters.

render was 5min to sl18.. needs a better normal map.



Now I know the sss render is nonsense, sorry about that, I did it a long time ago, thanks Tom, I've learnt something,.... cant wait to test the new maxwell...

[andyjacobs]

Thanks for the suggestions.

- Tom sorry I did a search for reflective not reflector. My bad.

I'm yet to model the object and try myself. I have a request from a client and was wondering if anyone had achieved it yet. Ill try today and let you know how I get on.

[andyjacobs]

Hi Eric,

Thanks for your suggestions. I think that would be the right approach if I was trying to model an object like this





But Im looking to have it as a detail on an item of clothing so more similar to the link I posted previously.



I like your mirror layer with the reflection being bright at 0º and dark at 90º I had a play with that really quickly today and its not bad.







I think the easiest would be if there were some way to fake it with a material that had an emitter as the 0º colour and dark on the 90º I tried a few things with emitter layer combined with the mirror layers in different strengths, but wasn't able to produce anything convincing.

[Mihai]

Are you sure that picture is not exaggerated in any way, what exactly are they reflecting so strongly? Is it a big emitter behind the camera? It's not like they can emit more light than they receive.....

[tom]

http://www.simonedecker.com/WorksWhitening3.html

[eric nixon]

Andy, I think the effect is the same but at different scales, even the fine fabric retroreflect is effectively a LENS on the outer surface.. This is needed to achieve the effect of light coming back out from the direction it went in - (think cats-eyes).

[tom]

It's quite hard to simulate this material accurately using normal/bump mapping. Ideally, it requires to be modeled accurately down to the microns or needs a dedicated shader.

[Bubbaloo]

I tried to model a single retroreflective lens (#2), but it's not working so far.



My failed attempt: