Infinite Diversity of the Materials
Creating the material is almost half of the Octane. This topic is perhaps the most serious and must be studied continuously. The times you used to create material by imaginary settings are over. It's time to stand on the ground of the real world and look carefully at your surroundings. Because if you want to create a good material, you have to know and understand the interaction between the material and the light in real world. How are the materials in reality? By the simplest definition, light photons hit the surface and act according to the properties of that surface. What affects the appearance of a surface is the structural and optical behavior of it. This behavior determines the way of interaction with the surface and the ray. When light hits a surface, three types of interaction occur:
1- Can be Absorption by the surface.
2- Can be Transmission to the other side of the surface.
3- Can be Reflected from the surface.
The combination of these three interactions usually occur. In reality none of these features are 100%. Because the Law of Energy Conservation always works. According to this law, you can not find the material that reflects or absorbs 100% in nature.
Some materials absorb certain wavelengths of light. They also reflect some of them. This effect is called fluorescence effect. Interaction of the radiance energy to the surface follows the Law of Energy Conservation. Accordingly, the sum of the energies absorbed, transmitted and reflected by a surface equals the sum of the energies coming to the surface. This rule applies separately for each wavelength. So, There is no need to measure of these three energy interactions separately. These quantities are determined in ratio to the incoming energy (ie, relative). These ratios are different for each material and surface geometry. However, these ratios seem to be more related to matter structure. Accordingly, for a material surface, these ratios are called absorbance, transmittance, and reflectance, respectively.
Now that we are traveling infinite variety of real materials, we need to know and understand the tools underneath. Octane was already good at creating the materials, but now it's getting closer to the reality thanks to the new BRDF models. In the upcoming chapters, we will examine Octane's classic materials and new BRDF models in detail.
Remember, all the materials in the real world, no matter how simple they seem to us, actually offers a magnificent world which we want to disappear, discover and enjoy. If you're ready now, let's dive into the depths of this world.