Materialism 1.5 – rough metal

Render1SIG

Render1

There are many types of metal, many uses for it, and thus more than one way metal ages. Here, I’m picking a few arbitrary examples and how I would go about recreating a specific look in 3ds Max and Vray, using an object modeled for my Haussmann series and a more complex material than those I went through in the first Materialism post. While this shader is object-specific, it may yield a few general principles to be applied to a range of metals. The render above shows the final result.

First two references, including a very bad Ipad photo I just made of a vintage kitchen ustensil.

Image1

Image2

Here are a few things we can pick up here:

  1. There seems to be two layers of reflection: a sharp, mirror-like one, that reflects objects in a crisp way; and a blurry one, with a very noticeable bloom effect, particularly around bright highlights.
  2. Because of micro-scratches and the curvature of the surface, the blurry reflections seem to have an anisotropic distorsion, i.e. They stretch more in one direction instead of bleeding around the highlight in a uniform way.
  3. Scratches in the reflective layer of the metal let a dark, dull base layer show through.
  4. There are white-ish spots – perhaps traces of scale where water has dried, perhaps grime. These do not completely obscure the reflective layer, but form areas of lesser reflectivity.

Trying to map things a bit before getting stuck in, this suggests we will need at least four layers:

  1. The underlying base layer – the naked metal, if you like – that appears below the scratches: dark, with low reflection, high glossiness.
  2. The mirror-like layer, with a crisp reflection: high reflectivity, low glossiness.
  3. The “bloom” layer: high reflection, high glossiness in the highlights and vertical anisotropy.
  4. The “scale” layer: whiteish, low reflection, high glossiness, semi-opaque.

Now, these layers will blend in a different way. 2, 3 and 4 will be overlayed over each other, with each new layer letting the layer below show through. Layer 1, on the other hand, will appear only where the metal has peeled off or been scratched. In other words, it will reside at the bottom of the stack of physical layers in the object and let no other layer pierce through below it. In shader language, this means that it will have to reside above all the others, using a contrasted opacity map to govern where it appears.

To make things simpler, I will therefore use two Blend materials. The first (MetalBlendMat) will be a mixture of layers 2, 3 and 4, and the second (FinalBlendMat) will merge this Blend material with the base material (layer 1) using a black and white map as a mix map.

This is how the object appears in the viewport. It is not the best unwrap in the world, with quite a bit of distortion around the “neck” of the vase. But it will do here. The image shown here is the map that will appear in the diffuse channel of all the VrayMtl.

Viewport1

Let’s start with the first layer of MetalBlendMat (layer 2 in the list above), which will deal with the mirror-like part of our metal:

RenderLayer2

This one is a very basic Ward shade.

It has the darkish base-metal bitmap in the diffuse. The same map is plugged into three different ColorCorrection maps and lightened considerably. One of them goes into the the Refl.Gloss. Channel with a value of 1% (hardly any glossiness at all). Two versions, one slightly darker, go into a falloff map, which is itself plugged into the Reflect Channel (100%). This is not strictly necessary but will make the object slightly more reflective at grazing angles, like a Fresnel effect but very subtle and easier to control.

Here are the structure and the settings for this layer:

Layer2

Layer2Mat

Now the “scale” layer (4).

RenderLayer4

This is a less “metallic” layer. I left it as a default Blinn shader. It uses a lightened version of the base layer in the diffuse; the same map as Layer 2 in the Refl. channel, but with only 30% opacity (meaning the white-ish diffuse layer will “show” through more); and a darker version of Layer 2′s map in the Refl.Gloss. channel, a 30% opacity (much glossier reflection). Neither falloff nor Fresnel effect here.

Layer4

Layer4Mat

Below the Bloom/Anisotropy Layer (3)

RenderLayer3

Again, I’m using a Ward here. In fact, this is just a slightly modified version of Layer 2. The differences are: No Falloff in reflection and the Reflect. map at 80%. The Refl.Gloss. map is a new, high-contrast bitmap that gives a rougher look to the glossiness channel (see map below) at 9%. Anisotropy is set at 0,5 (quite subtle) in the Z axis, using the object’s UV coordinates.

Layer3map
Layer4
Layer3Mat

Now let’s see how these three layers blend together in the first Blend Mat (MetalBlendMat) below. Notice the “scale” stains and the way the reflection bleeds in an anisotropic way above and below the highlights (more visible around the neck of the vase). There is also this interesting mix of crisp and blurred reflections that we saw in our reference photos. By now the render is getting noticeably slower.

RenderMetalBlendMat

As you can see in the settings below, I am just superimposing the mirror layer and the anisotropy layer using the default blend value of 100%, but the “scale” layer is on top of the stack and uses a new, high-contrast grey-scale bit map as a mix map, so that it is only visible in these areas where the “scale” or “grime” stains are visible.

MetalBlendMat
MetalBlendMatmat

We are almost done. We only need the final dull-metal “base” layer (1), which, on the object, would be below all the metal layers and, therefore, in our final blend mat, will sit on top of everything else and bring the final worn-off feel.

Here is how it looks like applied on its own to the object:

RenderLayer1

This is a Blinn mat, with a Fresnel effect applied, more akin to a plastic than to a metal, although it retains a certain reflectivity. The diffuse map is the same as for all the other VrayMtls (though duplicated here for clarity). This same bitmap is plugged into the Refl. and Refl.Gloss channels (100% and 50% respectively) via to separate ColorCorrection maps.

Layer1
Layer1Mat

All that remains is to plug MetalBlendMat and Layer1 into our FinalBlendMat using a new, high-contrast grey-scale bitmap to define where the scratches and worn areas would appear.

FinalBlendMat
FinalBlendMatmat

Here is the final result again.

Render1

… and the object (with a slightly different shader) in context:

Baron Haussmann

Hopefully this will be useful for other types of materials, and not just metals. Some of these effects can be applied to vintage plastics and even glass. Alternatively, other types of metals can include additional layers, such as rust, at the bottom or the top of the stack. One thing to remember when doing this kind of work is always to start from a real-life example and deconstruct it in a logical way before translating this outline into Vray language.

31 Responses

  1. This is a material tutorial I have been looking for. The only thing I miss here, is the textures like the “Tabletop” and MetalSweepHarsh.jpg which you show in the basic material editor. If I knew how those images looked, I could find somthing alike, but I do not.

    Anyway I have made somthing simular, but maybe you could add those texturemaps so we could see them.

    Kind regards
    Michael

  2. Sammy says:

    Fantastic! Thanks for your tutorial. Could you provide the screen shot about the fall off in reflection and colour correction in reflective glossiness dialog??

  3. BBB3VIZ says:

    Tom: Yes, definitely, UV-unwrapping is a hugely important part of material creation. This is essentially where modeling and shading meet. I am planning an hour-long talk at the SOA Academy in October on material creation and it will include some info on UV mapping and unwrapping, using UV sets, going back and forth between Max and PShop, etc. While this will be an SOA exclusive, it is definitely an issue that will be addressed on the blog in the future.

  4. Tom P says:

    Hello Bertrand, first off your work is amazing and very inspirational. The tutorials and tips that you have posted so far have been great.

    I was wondering, as part off your materialism series are you intending to do a tutorial on uvw unwrapping?

    I know there are plenty of tutorials on the web, but I am interested to see how you approach this, as you have a unique way of dealing with materials. I am very interested to see how you deal with the overall process as a whole.

    Tom

  5. Mike says:

    Hi there, why don’t you use fresnel on the sub-layers?
    Those metals look a bit plastic in the render below (apart form the rustic tin).

    The glass on the other hand is awesome :)

  6. Jakub Čech says:

    Hello Bertrand,
    I would love to ask about materialism, how do you know when each texture have the right lightness, saturation and contrast? How do you figure this out in your test, hdri scene?
    Thank you.

    Jakub

  7. Mathias says:

    Hi,

    I really enjoy the materialism miniserie. Thanks for providing insight. I am a hobby modeller.

    Greetings from Frankfurt am Main,
    Mat

  8. Hazem B says:

    Hey there, spectacular material there, rather realistic metal, i’m curious as to how you’d go about reproducing this material with maxwell material system,

  9. Awesome as usual Bertrand. Can you share with us anything about your photoshop work? How do you manage the texture creation for that great custom textures you use on your shaders and anything about normal maps creation? Thanks in advance…your work is so inspirative to many of us…keep pushing man!

  10. Irakli says:

    First of all thanks for great lesson.

    I’ve got one question:

    after using Color Correction, textures are losing their information and they become something like monochrome color (at least that was in my case). If it’s normal, will it be OK to simply use something like VRayColor?

  11. BBB3VIZ says:

    Elias, Def: You’re right in the sense of “glossiness values”. I.e. a high value of 0,99 would show crisper reflections than a lower value of 0.6. I guess I meant high glossiness as in being blurrier. Sorry if that created confusion.
    And yes, my understanding of a 100% mix @ RGB128 is that both mats would mix 50%. Feel free to correct me if I’m wrong. I would not use additive mode since it breaks the laws of physics and may make your mat look weird.

    tOm: Believe me, I know the problem. It’s always a struggle to find the time.

  12. def says:

    Well actually I had the same question as “elias” but since no one else noticed, I guessed I was wrong in a way.. :) but, crisp reflections need high values of glossiness..
    furthermore, I have a question about the “blending” of the various layers/materials: you mention that you blend “the mirror layer and the anisotropy layer using the default blend value of 100%”.. but you use no blending map and the value is 128 (grey color).. doesn’t this mean that the result will have half the strenght of each layer’s reflectivity? Would it be correct to use “additive mode”?

  13. elias says:

    Great tutorial! I need a clarification though where you say:
    “2. The mirror-like layer, with a crisp reflection: high reflectivity, low glossiness.”
    Did u mean “blurriness” instead of “glossiness”?

  14. tOm says:

    Hi Bertrand,
    Thank you for sharing your knowledge, it is much appreciated as always :)
    You say “go ahead and explore the concepts with your own assets”: well I would like to do so but I have to say that most of the time I have to fight with tight deadlines for earning fewer and fewer money due to global economic crisis and clients that refuse to pay an honnest price for 3d renderings. Sad and hard times we go through. If I would spend less time doing commisioned works, I would have more time to spend for exploring material concepts like this one. So I just wonder how you can find time to write such tutorials ? I think that every 3D artist, even the youngest one, has something interesting to share with the community. And I would like myself to have time to write tutorials on a blog just like you do. Don’t you never sleep ? Or, are you married with a super rich woman ;)
    Who knows what activity would we be involved in today if we were living at Durer’s times …
    Seriously man, you rock.

  15. BBB3VIZ says:

    Glad if this is being useful.

    Hany, Todd: To me, the point of this is not so much to assemble pre-made elements to reproduce the exact same image, but more to go ahead and explore the concepts with your own assets. In any case, most of the textures are modified versions of CGTextures photos, which would be pretty easy to reproduce. You could even try this with standard Grunge maps.

    CC: Good question. I think bump is a pretty crude effect most of the time. Although it certainly has its uses and I do use them, they don’t often tend to add much to a material and can even break the spell if overdone, which easily happens. Whenever I use them, I keep the effect as subtle as possible. When the material demands some more pronounced ruggedness, I tend to prefer normal maps and, of course, displacement maps, which I use a lot.

    Tsivolas: I do have a pretty long beard. But I’m only 84 years old.

  16. exwhyzee says:

    Great tut B. as always. I’m curious what cases you pick for materialism 2 (wood?, glass?,metal?, something else?)? And yeah, show you face, show you face! :D

  17. tsivolas says:

    Untill now I had in mind an old bald man with long white beard, around 100-120 years old according to his 3d knowledge and wisdom….
    Thanx again B.

  18. cc says:

    Very nice tutorial. Do you think that bump maps would add some more realism and detail, especially at short distances?

  19. Vini says:

    I’ll read this soon as I can, I have much respect for you for spending time creating this little tutorials! Thanks a lot for this. Best Regards!

  20. Great tutorial Bertrand! I really appreciate in-depth experiments in creating realistic shaders like this.

    Would you be able to post the texture maps for this shader. I’d like to try replicating this shader in the Blender Cycles rendering engine.

  21. Guif says:

    Pareil, j’attendais une partie 2 au materialism, mais la partie 1.5 est vraiment très intéressante. Donc merci.

  22. Hany says:

    Its Gr8 tutorials But without all textures its a bit hard to for us to follow step by step your tutorial and compare results

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