For the specular channel, we want the smooth parts of the object to have stronger highlights than the rest. We can do this by setting the overall value of the specular channel to zero, and then using a "Value" procedural set to 100% masked by a gradient responding to the "Smooth" weightmap.
To add to the realism we can add a Turbulence procedural to add texture to the highlights. Adding this sort of detail to the specularity channel is one of the best ways to make a surface look real.
With specular channel
In the end, I set the Value procedural to 120% in order to boost the highlights further. The "Colour Highlights" parameter on the "Advanced" tab was set to 70% in preparation for creating the colour channel. For details on the other parameters, download the finished object at the end of this tutorial.
Specular Channel:
To colour the anvil, I used these four components in the colour channel (in order from bottom layer to top):
Base Colour - The main colour of the anvil (set in the main surface properties dialog), set to
RGB = (81,70,68)
Smooth Colour - A "Value" procedural RGB = (141,132,126) masked by a gradient responding to the "Smooth" weightmap. Places colour highlights along the smooth parts.
Fractal Noise - A "Turbulence" procedural set to black at 50% opacity to add some dirt and noise to the colour channel.
Slope Based Rust - A gradient that places orange hilights on a particular gradient of slope. This
is then masked by another gradient to make sure it only applies to the bottom
section of the anvil.
With specular channel
Base Colour
Smooth Colour
Fractal Noise
Slope Based Rust
The four pictures above show how the colour changes as each component is added in turn. The picture below shows the colour channel mixed with the bump and specular channels.
With colour channel
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Diffuse Channel:
The diffuse channel helps the object respond to light in a realistic manner. It defines the amount of light that is necessary for the surface to show its colour.
For the anvils diffuse channel, I have used a mix of some of the layers from both the bump channel and the colour channel, so that the diffuse channel is in sympathy with the other features. Put simply, the bumpy bits will appear darker, as will the dark parts of the colour channel. This helps to tie together the overall texturing scheme, and assists in the making the surface look photo real.
With diffuse channel
Reflection Channel:
The final channel that we'll be dealing with is the reflection channel. The scene file that you might have downloaded earlier included a half sphere hidden from the camera to provide a reflection.
Turn on "Trace Shadows" and "Trace Reflections" in the rendering options. The reason shadows are turned on now is because it will plunge the front face of the anvil into darkness (providing you are using my lighting set up) and make some of the reflections easier to see and therefore to adjust.
The main reflection setting is set to 10%, and the texture has a "Turbulence" procedural layer set at 0% with 65% opacity to add detail to the reflective surface, in a similar way to the Turbulence procedural in the specular channel.
Finished Result:
All done! We're left with what you hopefully will agree is a fairly realistic looking metal anvil. I hope you've picked up some tips about using the surface editor and gradient layers along the way.
As I mentioned earlier, the major advantage to this technique is that we have the final surface defined in terms of the models weightmaps. We can adjust them in Modeller and immediately see the surface respond to those changes.
The main reflection setting is set to 10%, and the texture has a "Turbulence" procedural layer set at 0% with 65% opacity to add detail to the reflective surface, in a similar way to the Turbulence procedural in the specular channel.
