In this tutorial we will look at what PBR is, how the fundamental Textures are used to define a PBR Material in Substance, and most importantly, how they work together.
Video Transcript
Hello everyone! If you are here, you probably already know that Substance Painter is a software application that allows you to create Materials and Textures for 3D models. The 3D model files are imported into Substance Painter and, here, you can create Texture images, mapping them onto the geometries, and export those images so the object, complete with Textures, can be used in game engines such as Unity or Unreal to create video games or applications with virtual or augmented reality, in animation and rendering software such as Blender 3D, 3D Studio MAX, and Maya, or in real-time 3D visualization systems on the Internet such as Sketchfab, and much more.
Before continuing, actually before even talking about the program interface or importing a 3D model into a new empty Substance Painter project, we first need to explain what is meant by a Material.
A Material is a set of information that, when applied to a 3D object, defines how it will behave when illuminated and rendered in a virtual scene. Rendering, meaning the final image visible on screen, whether static or in real time, is the result of the interaction between light and surfaces in a virtual scene. On one side, we have the light sources, of various types, from virtual lamps to lighting environment Textures, and on the other side we have the surfaces, or in some cases the volumes, of the objects. Post-production effects can then be added to this initial result, but as the name suggests, these are actually effects and filters applied after the rendering process itself.
Alright, so a Material is a collection of information... but what kind of information?
Depending on the theoretical model, or "scheme", "method", or "paradigm", used to create the rendering, different types of information can be specified, each with its own characteristics. Substance Painter, in particular, allows us to define Materials that follow the Physically Based Rendering model, or PBR. Sometimes you may also find the acronym PBS, which stands for Physically Based Shading, referring to the shading of object surfaces.
In this tutorial, we will not go too deeply into PBR theory, which we will cover in a dedicated tutorial. Here, we will simply look at the fundamental Textures used to define a PBR Material in Substance and, most importantly, how they work together. Understanding these concepts is essential for creating and customizing our Materials confidently, without relying on guesswork while changing the parameters of one Material information channel or another.
To avoid making this video too theoretical, I will explain the fundamental elements of PBR and how they are implemented in Substance using a 3D model that already has Materials and Textures created in this software.
The Physically Based Rendering paradigm, as the name suggests, is based on a physical approach, meaning it is inspired by how things behave in the real world.
Materials can be specified using two workflows: Metallic and Specular.
In the Metallic workflow, surfaces are divided into metallic and non-metallic materials and, based on this distinction, all the other channels behave differently.
In the Specular workflow, instead, the intensity and possible color tint of the specular reflections are defined to determine how light interacting with the surface of the object will behave.
In particular, in the PBR Metallic workflow, which is the one used in this example, the appearance of a surface is determined by several characteristics, the most important of which are:
its nature, first of all distinguishing whether it is a metal or a non-metal, also called a dielectric;
its Base Color, which in a metallic object defines the intensity of the light reflections, while in non-metallic objects it actually represents the true surface color, without lighting effects;
the level of smoothness, or Glossiness, or conversely the level of Roughness of the surface across its various areas.
To these characteristics observed in the real world, additional features useful in the virtual world are added. For example, by using specific Texture images such as Normal Maps or Height Maps, it is possible to simulate the presence of details without actually modeling them into the geometry, saving vertices, edges, and faces, and therefore computational resources during rendering, especially in video games and other real-time applications.
The wooden barrel I am using in this video allows us to examine, within a single object, how these basic pieces of information are translated into Textures and combined together in a Substance Material.
To display the preview of the complete Material applied to the object in the 3D View, I press the M key, for Material, or select Material from the drop-down menu at the top right of the 3D View.
As you can see, we have both metallic elements, made of iron, and non-metallic elements, made of wood. This will allow us to appreciate the differences in how these two types of materials are handled in the PBR paradigm, especially regarding their Base Color definition and the colors of the specular reflections.
To display the individual information channels, which correspond to the different Texture images applied to the object surface, we can press the C key multiple times or choose the desired channel from the drop-down menu at the top right of the 3D View.
Let's start with the Metallic channel, which defines which parts of the Material should be treated as metallic and which should not, using a grayscale image where white represents a pure metal and black represents a pure non-metal. In the case of this barrel, we also have gray areas because the material used for the metallic parts, "Iron Old", is meant to represent worn old iron, perhaps covered with dust or rust, which lowers its "metallicity", so to speak.
The wooden parts, on the other hand, appear completely black, meaning non-metallic, as expected.
Let's move on to the second fundamental PBR channel, Base Color.
As you can see, this information channel displays the base color of the object using a color Texture, without lighting or shading effects. These are, so to speak, "flat" Textures. The colors of the metallic parts and the wooden parts have similar intensity levels. The colors are different, of course, but visually they do not seem radically different, even though they belong to completely different substances.
The reason is that the distinction during shading and rendering is made by Substance using the Metallic channel and its related Texture, which tells Substance that light reflections must be handled differently depending on whether the surface is metallic or non-metallic. The gray values in the Base Color of the metallic parts define the intensity of the light reflections and any possible color tint applied to those reflections.
The Iron Old material is a "dirty" material, so the effect is not very noticeable, but look at how things change in the various channels and in the final result if I insert a Substance "Aluminium Pure" Material between the wood material and the metal material and disable the underlying Iron Old material.
In the final result, meaning the Material view that combines all the information channels, the metallic parts appear MUCH more reflective than before.
In the Metallic channel, the metallic parts are pure white, representing a perfectly pure metal.
In the Base Color channel, the metallic parts are almost white, indicating that the intensity of the specular reflections in those areas will be at its maximum and without any color tint.
Now look at what happens if I set the Metallic parameter of Aluminium Pure to zero: the metal bands become white, they no longer reflect like before, and they look like white plastic objects.
Now let's set Metallic back to 1, but reduce the Base Color value: the bands maintain the typical reflectivity of metal, but gradually become darker.
This is the key point: in the Metallic workflow, like the one used here, the Base Color of an object alone is not enough to define how reflective a surface will be, because we also need to specify whether it is a metal or not. In a metal, the intensity of the Base Color is also the intensity of the light and specular reflections, while in a non-metal the Base Color only defines the actual surface color, as happens with the wooden parts of the barrel.
I am keeping the Aluminium Pure material enabled and Iron Old disabled to show you the effects of the third fundamental Material channel: Roughness.
Roughness, which is the opposite of smoothness, is represented like the Metallic map using a grayscale image, where white represents maximum roughness and black represents a perfectly glossy, fully reflective surface. In fact, a perfect mirror is implemented in PBR using a metallic Material with pure white color and Roughness set to 0, as I am showing on screen right now.
By increasing the Roughness value, we make the surface less smooth and therefore its specular reflections become more diffuse, or blurred, in a sense. This applies to both metals and non-metals.
I am now removing the Aluminium Pure Material and reactivating Iron Old to return to the original project configuration and take a look at some additional information that, in Computer Graphics, allows us to add surface details during rendering without physically modeling them into the geometry.
I then select the "Normal + Height + Mesh" option from the selector at the top right of the 3D View.
This view shows the combination of multiple information channels that influence the simulated details on the surface of an object. Without these details, the surfaces of the object would appear smooth and not very believable, especially in the wooden areas.
In particular, in the example shown on screen, the surface details are mainly implemented in the wooden parts by the "Fibers" layer. To observe the differences in the appearance of the surface with and without those details, simply enable or disable the corresponding layers in the Layers panel while observing the differences both in "Normal + Height + Mesh" mode and in "Material" mode in the 3D View. The differences become more noticeable when the object is illuminated with side lighting rather than frontal lighting.
Similar effects are also present in the metallic parts, implemented using the Height and Normal information channels of two Iron Old layers, Iron and Edges. As you can see, these Textures make some surfaces much more interesting, whereas without them they would appear unrealistic because they would look too smooth and too flat.
A Material is a set of information implemented through images, some grayscale and some color, mapped onto object surfaces and combined according to a specific method, which in our case is the PBR Metallic paradigm. This information defines how the object surface and the light sources interact to produce the final image.
PBR is based on material characteristics observed in the real world and implemented in Computer Graphics by properly combining Textures that represent those characteristics.
The PBR method includes two workflows: Metallic and Specular. In this tutorial, we examined an example using the Metallic workflow.
In the PBR Metallic workflow, the first step is defining, through a grayscale Texture, which parts of a surface are metallic and which are not.
In metallic areas, the Base Color information, which is a color Texture, defines the intensity and possible color tint of the specular reflections. In non-metallic areas, Base Color only represents the true surface color, without lighting or shading effects.
Roughness indicates the degree of surface roughness. With low Roughness values, reflections are very sharp and well defined, and in a metallic surface with a white base color the material behaves like a perfect mirror. As the Roughness value increases, light reflections become progressively more diffuse and blurred. Roughness is the opposite of Glossiness.
Normal Textures, which are color images, and Height Maps, which are specific grayscale images, make it possible to simulate the presence of surface details during object visualization and rendering. They are useful for saving geometry and therefore computational resources, especially in real-time applications such as video games or virtual and augmented reality applications.
Alright, for this introductory videotutorial on the basic elements of PBR, Materials, and Textures in Substance Painter, we will stop here with these first four information channels. I will create additional tutorials in which I will analyze individual channels separately, such as Height and Ambient Occlusion, or alternatively examine all the channels of a Material together to see how they combine to produce specific effects, depending on the case.
Feel free to leave questions, comments, and requests in the comments section of the video on YouTube. See you next time!