Tutorial 2: Advanced Specularity Control

One of Gaffer's main features is its Specularity control. It gives the user enormous influence over the behavior of specular highlights, including defining the exact shape, blending, width, sharpness, anisotropy, edge strength and falloff, and even color of the highlight. Multiple highlights can also be superimposed, which is critical for many surfaces such as paint. LightWave gives you one single control over specularity shape, "Glossiness." Gaffer provides thirty-two separate controls. This much control may seem like outrageous overkill, but in fact it's a necessity to match the behavior of real surfaces.

In our last tutorial we set the stage for surfacing an urn. We'll begin by loading "spec_urn.lws" into Layout. This is what your scene should look like if you completed the last tutorial. What we want to achieve here is to create a very polished and thick lacquered, painted surface. This kind of surface has a distinctive, rich look, even without texturing, due to its complex specular behavior.

We'll start by coloring the urn and starting to move towards the basic characteristics of a red, lacquered paint. Open the surfaces panel and set the urn's surface color to 200-0-0. Set the diffuse value to 75%, specularity to 100% and reflectivity to 10%. For now, let's disable the fill lights so they're out of the way (we'll turn them back on later.) Go into Gaffer's options and set the "boost" value for the "Fills" to 0%.

Gaffer has a small surface preview to help see the effect of different controls, so lets set that up so we don't have to do multiple test renders. We have to tell Gaffer about the kind of surface we want to preview, so in the bottom-left of Gaffer's interface, set the preview diffuse to 75%, preview specular to 100% and preview color to 200-0-0. This matches the basic surface settings that are set in Layout's surface panel. The preview now shows a simple shaded red ball, which will update as we set the more advanced Gaffer options.

A surface such as the one we are trying to create has a very tight hotspot (usually the same color as the light causing the spot since it's actually a reflection of sorts) and a broad underlying hotspot caused by the coating or layers of paint. This is usually reflected as the color of the paint itself. Let's first create the bright, white, center hotspot. Set Gaffer's "primary specularity" to 100% and the color to 225-225-225. Set "Gloss" and "Sharp" to 90%. These numbers were chosen simply by watching the preview as different values were chosen to match the behavior we had in mind.

Now we'll add the second specularity, which has a broader, colored, highlight. Set the "Secondary Specularity" to 100% to activate a second specularity channel. For this type of surface we want this hotspot to be a bit brighter tint than the base surface's color to give it an electric look, so set the color to 225-0-0. The preview shows this effect. We want a slightly tighter highlight than the default (but not as tight as the first, white, specularity) so set "Gloss" to 70% and leave "Sharp" at 50%.

We're ready for a a test render, so close Gaffer's panel and re-enter Layout. Open the camera panel and turn on "Trace Reflections". Render a frame.

Looking at the frame, we're getting there but the secondary hotspot needs more work. It's too narrow and too bright. Go back into Gaffer. By experimenting (and again watching the preview) we set "Gloss" to 80% and "Sharp" to 25%. Bringing the sharp value down will broaden the hotspot while raising gloss will compensate for the difference by keeping the hotspot visible and not allowing it to be washed out. Finally, let's bring the color down a bit, to about 172-0-0. We can do this one of two ways. One is to open the color panel and manually adjust the tint. A second, quicker, way is to right click and drag on the color gadget itself to raise and lower its brightness.

Exit Layout again and render the scene. The urn, with no textures at all, is starting to have some real character. Yet all we've done is tweaked its surface shading! This illustrates how important the shading model really is when you're trying to create photoreal effects.

The next tutorial will keep using this urn as an example, and show the effect of anisotropic shading.