How do you create old and rusted chrome?

[thomthom]

I'm trying to make a render out of an old car. But I'm really having problems making the old rusted chrome look right.

I tried with a low glossy reflection, which turned out noisy. So I increased the subdivisions, but that also greatly increased the render time. And it still didn't look very good.

I tried with a 0.9 Glossy and added a noisy opacity map for the reflection. And I set the diffuse to a light blue-grayish colour. That helped rendertime allot. But still not looking great.

I've been looking on the net, but most just describe perfect polished chrome. Best I could find is http://features.cgsociety.org/story_...?story_id=2613 but it only roughly describes the concept, which was what I was trying to do myself anyway. But I just can't get it working properly.

I'm using an HDRI for background and GI so there'd plenty of stuff to reflect.

Some reference pictures: http://jalopnik.com/cars/down-on-the...oll-273476.php

Anyone got some tips?

[thomthom]

Re: How do you create old and rusted chrome?

I came across this tutorial; http://asgvis.com/index.php?option=c...d=30&Itemid=57
I'll try it tomorrow. But I'm still interested in hearing other suggestions and methods.

[40th]

Re: How do you create old and rusted chrome?

Thanks for the tutorial link, very useful.
Good luck with the car material, anxious to see the result.

[stefanq]

Re: How do you create old and rusted chrome?

It's a good idea to start not with chrome material...I think...you should try for example, platinum blurry, and then apply the steps from that tutorial.

[thomthom]

Re: How do you create old and rusted chrome?

That tutorial seems to have set me in the right direction. But there's a couple of things that's unclear still:

1. In that tutorial about old metal, the first fresnel layer have a 50% gray. And an IOR of 20. But what should the second reflection layer have? Identical? or should the reflection be 100%?

2. Why is the IOR of the two layers be the same? If they are, then I don't understand why you can't just use a single fresnel layer with a glossiness that lies inbetween the two described in the tutorial.

3. Is the refract IOR important? I thought it only mattered for transparent materials.

[40th]

Re: How do you create old and rusted chrome?

1. According to the tutorial the reflaction should be in both refl. layers the same (50% / 125). The difference between the layers shows in the Reflection & glossiness highlight, one layer should have Reflection & glossiness highlight>0.98 and the second layer>0.8

2. The IOR is the same because it sets the amount of the reflection, but for this effect he used to different highlights of reflection and glossiness.

3. The higher the IOR (in ref. layer) then more reflective the material.

p.s. all i wrote is how i understand the things, if i'm wrong please correct me.

[thomthom]

Re: How do you create old and rusted chrome?

3. The higher the IOR (in ref. layer) then more reflective the material.

I thought that's what the reflection IOR did...?

[40th]

Re: How do you create old and rusted chrome?

3. The higher the IOR (in ref. layer) then more reflective the material.

I thought that's what the reflection IOR did...?

I'm sorry Thom, I didn't understood if it's a question ?

[thomthom]

Re: How do you create old and rusted chrome?

I thought it was the reflection IOR that defined how reflective the material was. And I was wondering what the refraction IOR did.

[40th]

Re: How do you create old and rusted chrome?

Of Reflection IOR i believe you thought right.
Quote from spot3D.com:
Refraction IOR - index of refraction for the material, which describes the way light bends when crossing the material surface. A value of 1.0 means the light will not change direction

Here you can find examples http://www.spot3d.com/vray/help/150S...refraction_ior