Tutorial 3: Anisotropic Specularity

Another great feature of Gaffer is Anisotropic Specularity. This allows for realistic shading of surfaces such as scratched or polished metals, hair, or threads, where the surface has a very complex specular behavior due to the fine detail on their surface. In this tutorial we will create two surface types that in real life would show this type of specular behavior, a brass surface and an aluminum alloy surface.

Load "aniso_urn.lws" into Layout. This is the scene as we left it from the last last tutorial.

Anisotropic highlights are broadened in certain directions. You define these directions by the use of an auxiliary object that can be positioned and rotated to tell Gaffer the behavior you want. We'll start by adding this control object, so open the objects panel and choose "Add Null Object". Parent the null to the urn, and stretch the null along its +Z axis so we can clearly see which way it is pointing. (This stretching is unnecessary but helps us see the direction much easier.) Rotate the null 90 degrees in pitch. This makes the null's Z axis point along the Y axis of the urn. We'll be adding a "Cylindrical" anisotropic geometry, causing the highlights to be broadened along this axis.

Now we'll set up the surface to have a brass-like behavior. Open the surfaces panel and choose the urn's surface. For this example set the surface color to 225-175-0, set diffuse to 50% and reflectivity to 0%. Open Gaffer's options.

We want to turn on those fill lights, since metals respond much better to multiple lights. Set the "boost" of the Fill lights to to 50%. As before, let's set our preview up to show the surface. Set "Preview Diffuse" to 50%, "Preview Specular" to 100% and the "Preview Surface" color to 225-175-0.

Now we'll define the anisotropy itself. In the "Anisotropy Direction" section of Gaffer, type in "Null" (it's case sensitive) for the "Control Object" and set the type to "Cylindrical". If you've done everything correctly so far you will notice the green "Y" next to the "Control Object" field. This means "YES, I've found the object." If you've misspelled the object or the object doesn't exist, you will get a big "N" for NO.

This type of surface is much easier than the previous lacquered surface. A single fairly broad highlight with a similar tint to the base surface works very well. Set the "Secondary Specularity" to 0% to disable the second highlight. For the "Primary Specularity" section, enter a color of 225-175-0, gloss of 60%, sharp of 20% and "Anisotropy" of 100%. Looking at the preview, this looks great. Return to Layout and render a frame. Applied to our urn, we can see the more subtle effects of the shading. The highlight could be a slightly brighter tint, so back in Gaffer, right click and drag on the specularity color gadget to raise its brightness a bit.

The next example depicts an aluminum alloy as seen on thermoses, camping utensils, sprockets, gears, and all kinds of other fixtures. We've covered the features needed to get a surface such as this in the last two examples, so we'll just load a ready-made surface. LightWave's saved surfaces can include plugins like Gaffer with no problem!

Load "aniso2.srf" onto the urn's surface using LW's "Load Surface" button. Open up Gaffer's options and see how this surface is defined. We've used two specular hotspots in combination with anisotropy for each. Experiment with various settings to suit your tastes! We hope we've given you enough information in the last few tutorials to get you started with realistic specularity with Gaffer.