Finally got a working version of tuhopuu and tried the Blinn shaders, trouble is I can’t work out what exactly the Drough and Srough and IOR do…
One seems to make the material darker when increased and one makes it lighter when increased, other than I that I can’t see the difference. (And how can a solid material be affected by altering a value of index of refraction???)
So my question is, what do these properties do and what are the advantages of using Blinn?
Does anyone know if there any tutorials anywhere on this topic? I haven’t been able to find any.
Well, since I implimented the feature, I suppose I can answer your questions.
Yes, the names are rather confusing. Unluckily, there isn’t enough room in the interface to have larger buttons with more explanitory names. The button names should be: Specular Roughness (SRough) and Diffuse Roughness (DRough).
SRough: The higher the SRough, the more broad and “rough” the specular highlight will be; the lower it is, the sharper the specular highlight will be.
DRough: The higher the DRough, the rougher the diffuse aspect of the material will look. This is a concept that a lot of people are unfamiliar with, but is very important. A good example of a “rough” surface is the moon: the next time you see a full-moon, notice how it is lit very uniformally over its surface. That is because it has a very rough surface (and it doesn’t have any significant specular highlight).
The reason that increasing DRough makes it darker is because of microscopic shadowing. On the microscopic scale, rough surfaces are kind of like a vast mountain range, thus when light is cast on the “range”, the “mountains” cast shadows on each other, darkening the average intensity of the surface. But the darkening (from those shadows) is only one of the effects of the roughness.
BTW: you can compensate for the darkening by increasing the “ref” value.
IOR: Well, it turns out that the amount of light that bounces off of a surface is dependant on its IOR. It’s basically a more physically accurate version of the “spec” slider. Of course, you will notice that the spec slider is still there as well (under the “ref” slider), just incase you want to use that, too.
BTW: an IOR of 1.0 gives no specular reflection, and the higher the IOR, the brighter the specular highlight will be. However, even at an IOR of ten-zillion, it will never reflect more light than is hitting it. So, to get even brighter highlights, you can set the “spec” slider to more than 1.0 (the specular brightness is multiplied by the “spec” value).
