How to build a Shader for Anodized Aluminium

Question

I have modelled this smart phone based on Iphone 6 reference images. The rendered image of the back of the phone looks like this:

If I look at real life images of this "Iphone 6 Space Gray" I feel that "my phone" misses some fine grain and a "metal sheen". Like these images

My shader looks like this (like suggested here)

I would like to build a shader that gives a realistic look of the apple iPhone space gray material. I also had a look here ... this shader is based on an anisotropic shader which I feel that should be the way to go. It also has the fine grain ... but I don't think it is the solution (and this is also too complicated for me; I would like to understand it). So .. how to build a realistic shader for this apple material ?

Concerning the proposed solutions: I really like the solution suggested by PGmath. When applying his material to my iPhone this is the result.

As I am intrigued by Physically Based shaders I picked up the suggestion of Paul Brachmann and proposed a PBS based solution using the work of PGmath

Answer 1

Here's what I have come up with.

The shader consists of a little bit of diffuse mixed into some fairly rough gloss, with a smoother Fresnel gloss mixed in at the end. I also noticed that the gloss on you reference image has a very slight, yet distinct, variation in reflectance across the phone. To simulate this I added a noise texture controlling the roughness of the two glossy shaders.

Here is my node layout:

Click to enlarge.

A few notes:

• I am using Geometry > Position as mapping coordinates for the noise texture to get even scaling. Using generated coordinates on an object with a non-cuboidal bounding box results in stretching.
• I use an RGB Curves node to bump up the contrast.
• All the math nodes just remap the [0,1] range of the texture to the desired ranges for the glossy roughnesses.
• The colors in the above node layout are for the gold shader on the right of the render. The silver one just uses grey in all 3 shaders (light grey for the glosses and slightly darker for the diffuse).

Answer 2

I came up with this physically based shader:

Basic Setup (including custom pbr node groups):

I hope you can use it as a starting point for your final shader. But of course it largely depends on your lighting situation how the shader actually will look (although pbr certainly helps).

Answer 3

Maybe a bit stupid to answer my own question but both the answers of PGmath and Paul Brachmann have made me try to work out a third option. Recently I watched these videos of Physically Based Shading and I rebuild the Metallics shader explained in this tutorial. Now as suggested by Paul Brachmann I have added the noise texture node to this shader. For this I used the work of PGmath as explained in his answer. This is the resulting "PBS Anodized Aliminium Shader". I hope I have understood the PGmath shader correctly and rebuild the Metallics shader correctly.

Anyway this is the result of the render (using the test setup of PGmath). The silver object has the PBS shader, the gold object the PGmath shader.

Answer 4

I stumbled on this old thread when reading about anodized aluminium.

Am I completely on the wrong track by saying that the recently (2016?) introduced Anisotropic shader does exactly what the shader by @PGmatch does above? (And by extension also the principled shader, if used mostly for it's anisotropic slider?)

In the screenshot below I just downloaded @PGmaths blender file, added a HDR texture instead of the lights and duplicated one of the cubes with a simple Principled shader?