Reflective Dispersion

[isoparmesan]

This might be a kind of basic question, but I'm not exactly sure what to search for.

I need to make a material that is a brushed or sandblasted metal. I have a real world example to work with, and I'm noticing that the closer an object is to it, the clearer its reflection. It also has the property of near mirror like reflections when viewing from a glancing angle. I know the second bit is accomplished via the Fresnel parameter, but how would I control the first bit? I've seen this effect described as "dispersion" but when I search for that I mainly find thing relating to refraction which isn't what I'm looking for.

[Intuition]

Are you talking about turning down the glossiness? Glossiness at 1.0 is like a mirror OR if fresnel is on it is like a clear coat. Then you can take the glossiness down to break up the reflection like brushed metal, etc. THEN on top of that you can use anisotropy to help bend the reflection vertical or horizontal essentially helping the brushed metal effect a bit. Use it sparingly along side a glossiness value of 0.600 and 0.780 and you will begin to see the object reflection get blurrier the farther away it gets from the surface.

Dispersion and Aberration have to do with the light getting cut apart by wavelength and you end up with the prism effect.

[Rens]

What you're looking for is the glossiness parameter, which is a measure of how smooth a surface is. Black being very rough and white mirror-like smooth. This by itself has the effect of objects being nearer to the surface appearing clearer or more defined.

The second one is where the light gets less scattered at grazing angles, basically appearing as through the surface is smoother, which it likely is at those angles.
You can do this with two glossiness maps, one for head-on lower smoothness (lower glossiness), and one for grazing angles higher smoothness (a higher glossiness value).
You then need a blend node to blend the two together. For the blend value you need a falloff, samplerinfo type input, so the higher glossiness value gets used for the grazing angles. Don't have maya open so you'll have to figure out the details, but basically you make the material less rough towards grazing angles, that will do everything you described. : )

[isoparmesan]

Does the glossiness parameter actually behave that way though? I'm going to do some tests, but to me it's always seemed like it uniformly blurs reflections regardless of their distance. I'll post what I find.

Thanks for the idea of using the blend node for controlling glossiness based on the viewing angle. I mentioned that I've used fresnel to control this, but then I realized that the fresnel IOR really controls the amount of reflection based on the viewing angle, and not the glossiness. I'll give this a shot too.

[Algehov]

You've probably figured it out already, but yes it behaves that way.

Example:


You actually get abit of a "mirror like" effect at high angles too, but if you wanna exaggerate that effect I suggest you do what the others said. Plugging in a sampler info into a ramp and control the glossiness at the edges and the front that way. Then play around with the anisotropy amount to match your reference (and potentially flip the effect 90 degrees by putting the anisotropy rotation to 0.25)

[isoparmesan]

well, that definitely illustrates the point. Thanks for posting that.