Galvanized steel using procedural maps in 3dsMax

Galvanized steel is a material often used on larger structures like hangars, gates, houses etc. A procedural attempt is useful for avoiding additional unwrapping on background objects for instance.

My target is to create a material with a slightly grey/blue diffuse, which results from different cracks of zinc, a slightly grainy surface and some broad highlight

My main focus on that tutorial is rather on the set up of the desired material than on specific values. Result differing from mine can be rather the rule than the exception, so try out on your own. I used release 6 on this with no plug-ins, except for the lighting where I used the well known e-Light script

A few words about the geometry

Apart from the mighty mighty teapot of death and a cylinder I 'm using a beveled C-ext object on this. You can try out without beveling, but it adds a lot to the desired look and feel. My lighting setup is an e-light and an array of 9 instanced omni light with disabled diffuse lighting to kick the highlights a little bit more.

Diffuse

To get the color information for my basic diffuse color I open the reference picture in PS, drag a selection of my choice with the marquee tool and blur it until there are no more detail visible. Using the eyedropper tool gives me the RGB values which I use for the diffuse of a standard material.
This won't be final, it's just a base to start with, I will explain how to improve later on.

Highlights

For my highlights I use a Glossiness near or equal to zero and a Specular Level around 50.

The grainy surface

For the Bump Map I choose a Noise map, set to fractal. With lowering/increasing the High/Low Threshold to values around 0,5 I increase the contrast of the Noise colors. The size depends strongly on the size of the object, a good rule by thumb is that you should rather kinda 'smell' the Bump map than see it, this requires a little trial and error.

This Bump Map breaks up the clean surface, clearly visible on the edges of the highlights.

At this point the material should be good enough for a quick and dirty aluminum or zinc material, but I' far away from the final version, so let's get it on.

Diffuse

For creating the cracked look of the diffuse I use a Cellular Map with Cell Characteristics set to Chip. The size is a matter of choice, it should match the proportions of the reference picture though. I lower the Spread that much the lines nearly disappear. Into the lower slot of the Division Colors I drag a Noise map, type set to fractal, colors around an RGB 128 and a little tone of blue. I increase the contrast via changing the values of High an Low Threshold. With this map I try to break up the uniform color of the Spread, if it doesn't work, try changing the values for size, levels or coordinates.

One level up - back in the Cellular Map - I equalize the values for the High and Low Threshold toward the Mid Threshold and - last but not least - increase the value for variation. Much better now, but I'm still not satisfied, so I copy the cellular map into the Cell Color slot and open it. In this map I do the same stuff like one level above, instead of using another map in the Cell Color I change the colors to some light grey with a little cyan or blueish tone and change the values for offset, tiling and rotation.

Back in the maps roll out I decrease the value for the diffuse down to 50.

This setting is not final, it should be changed after adding the next step, which is

Highlights

I instance the Diffuse Map into the Specular Color slot and do a test render. If the colors are oversaturated I decrease the values for variation and the saturation of the colors in both Cellular Maps.

The value for the Specular Color can be left on 100.

Instancing the Diffuse map into the Glossiness and lowering its value to around 30 is quite the last step.

The blurred reflection adds a little extra to the material. It increases the render times drastically, but I think it's worth the time.

Add a Mask Map in the Reflection Slot, in the Map Slot I put a Fresnel Falloff Map, in which Side Slot I add a Raytrace Map.

For the Mask Map I use another instance of the Diffuse map, which I invert by checking on the Invert Mask box.

In the Raytrace Setting of the Renderer I lower the Depth to 1 and change the Blur Aspect and Blur Values in the local Fast Anti-alias Settings of the Raytrace map. Especially the last step boosts up the render time.