Another common usage of specular block is making glass materials. In that case you usually don’t need the diffuse block enabled, just the specular one. Here is a simple example:
Note that the shape is barely visible. The reason is that all you see at the moment is reflections, and as the N is 1.5 (like plastic or water), you don’t really see a thing. It looks like a soap bubble without those color effects (see below). In order to make it more realistic, we need to tell Koru to simulate refraction, so the material refracts the scene behind. You can do so by increasing the refraction level parameter. Let’s set it to 10:
Now that’s glass. You can tint it up using Transmission parameter, that controls the light going through the layer:
That’s how you make colored glass in Koru. You can make a “frosted glass” effect by increasing the roughness level:
Exactly as with opaque materials, you can have several specular layers to make a more complex material. Use mask and transmission parameters to control the light coming through the layers.