Base color

Defines the color of a material (sRGB texture or a solid color). Base Color additionally contains a Color Picker to pick a specific color from a selected pixel.   

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Roughness

Is a linear grayscale texture, or a solid grayscale color. Defines how glossy/rough the surface is. 

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Metalness

A linear grayscale texture, or a solid grayscale color. All physically based non-metals (dielectric materials) have the value 0, raw metals have the value 1. Anything between is used for impure metallic materials, such as rusted metal.  

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Normal

A texture that fakes the lighting of bumps and dents. Used to add details without using more polygons. 

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Opacity

A linear grayscale texture, or a solid grayscale color. Defines how transparent the material is. The interesting part comes with an opacity texture, where you are able to create holes in an object, for example, without touching the geometry. Pure black stands for 100% transparency, white for 0.  

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Refraction

Setting refraction to a non-zero value will set the object to transparent, so you are able to create a glass/water like material. Do not lower the opacity for those types of materials. Lowering opacity dims reflections, refraction doesn’t.  

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IOR

When light passes through a transparent surface, the light is typically bent or distorted. This distortion is known as refraction, and the amount of refraction is known as the index of refraction (usually, the more dense object, the higher the IOR value will be). Every transparent material has its specific IOR value (here is a list of measured values for hundreds of materials - https://pixelandpoly.com/ior.html ).  

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Ambient Occlusion

Defines how exposed each point in a material is to ambient lightning (how bright light should be shining on any specific part of the surface). 

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Reflectivity

The intensity of reflections on a material. This value is usually really low – for most of dielectric (non-metal) materials, it’s between 0.02 – 0.05. The reflection of metallic materials is handled with metalness, not reflectivity

Emission

Intensity and color of light emitted from the surface. When an emissive material is used in a scene, it appears to be a visible source of light (therefore, with emission you can create a light bulb, for example).  

Texture Transformations

With texture transformations, you are able to tile (and therefore change the size) textures and adjust their positioning through offset. All of those options are available as a local setting in every material’s parameter which contains texture, or globally for the whole material.  

Double-sided Material

In 3D modeling, single-sided materials are visible (rendered) only from one side. Double-sided material achieves visibility from both sides of a polygon.