My general approach to metal has been this: (for a polished chrome)
VRayMTL
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diffuse - dark gray
reflect - 255,255,255
fresnel on
IOR - 7.0
gloss - 1.0
for something like a brushed aluminum I might do this
VRayMTL
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diffuse - dark gray
reflect - 255,255,255
fresnel on
IOR - 7.0
gloss - 0.7
However after looking over IOR Charts, I realize that aluminum has an IOR of 1.4. If I put this in my aluminum’s ior it barely reflects and just looks terrible.
Clearly for metals I am jacking up the IOR to get the proper reflectivity, however I must be doing something fundamentally wrong. Can anyone enlighten me?
Far as I know aluminium and other metals are electric materials so they don’t use Fresnel laws - again I’d go with a reference of what it’s supposed to look like and work towards it rather than relying on tables.
Joconnell - Many thanks, this is what I was hoping to hear, and it’s what I’ve been doing.
What works well for both of you? I’ve seen your brilliant renders and was just curious how you attack it. Falloff maps in the reflect slot? How would you make a polished chrome material? or a brushed aluminum?
If you’re going to use a low IOR on a metal, like the 1.4ish for aluminum that you mentioned, then you’ll want to turn off fresnel reflections and use normal reflections instead.
How are you guys changing the IOR for the reflection? It’s not available (greyed out). I’m sure this is a simple thing, but I’ve been stumped on this for a while now.
To be honest, I’ve never bothered with IOR for metals. To be even more honest, I don’t really understand why metals *have* IORs - its not as though they are refracting, is it??? I thought IOR only came into play in the bending of light ‘through’ a material.
Quite right richard - apparently there’s three things that the energy can do, be reflected, refracted or absorbed. The ior will affect the amount of absorption as well as the reflection / refraction but this only happens in the case of dielectric materials where fresnel laws apply. In the case of electric?* materials such as metals they don’t have any fresnel incidence angle effects.
Right. We learn something new every day…and promptly forget it!
I may start to look into IOR and fresnel in future projects to see how it affects things, but at the moment, I am happy faking it using falloff in the reflect slots.
