Diffuse materials are simple materials compared to the other types. In this material, when the photons hit the surface, they are reflected in many different directions irrespective of the angle of incidence of light. If the surface is a smooth surface, the distribution of the photons is hemispherical, but there is no perfect smooth surface in nature. In reality all surfaces are more or less rough. It is therefore more reasonable to describe the diffuse reflection over rough surfaces. So, when photons hit a rough surface, they are scattered randomly instead of a hemispherical scatter. They do not vary according to the angle we look at, so these surfaces look almost the same according to any direction we look at. Such surfaces are called "Ideal diffuse (matte) surfaces" or "Lambertian surfaces." The directional semi-spherical reflection for the Lambert surfaces is often called "diffuse reflectance" or "albedo".
The above information is correct only if you want to use the diffuse channel. On diffuse surfaces, you may encounter information such as there is no reflectance etc. etc. However, this is partly the wrong information because in reality there is no 100% diffuse surface. In general, all surfaces coexist with Diffuse, Reflectance and Transmission. Some of them may have diffuse features. Surfaces such as carpet, matte paper, asphalt or fabric shows more diffuse properties than reflectance or transmission. But even on a piece of paper, if you look carefully you can see things like reflectance and fresnel. You can even observe Subsurface Scattering when you look at the sun behind that paper. Likewise on a fabric, on a tree leaf. So even creating a simple paper material is not as simple as you might think. For example, while asphalt roads show diffuse properties, they are actually both diffuse and reflectance characters. Just look at the road in a sunny day at grazing angles, you will see the reflectance and fresnel together beside diffuse.
All of these because the dual character of the light: Wave and Particle. Let's hope we find a solid mathematical proof of how these two things work together. Maybe it'll be easier then. But now you are standing right in the middle of the Realistic Render Engines; so we recommend that you observe and practice the features of the light and material you will create.
Now let's explain Octane's Diffuse Material properties:
The Diffuse parameter gives the material its color. In computer graphics terminology this is also referred to as “Base Color” or “Albedo”. Diffuse color can be can set using a value or by using a procedural or image based texture (will be explain in textures section). There are a few options here, let's take a look:
Color: Here you can set the Diffuse Color. If you need to make the colors black or white, do not enter "full black or white" values. There is not exactly white and black material in the real world. Also the following float value is a greyscale value. It is recommended that you use float if you are going to create a color between black and white.
Float: This option actually creates a gray scale value. If the RGB color is zero, this float value creates black for 0 and white for 1. The float here also works the same in Roughness, Bump, Normal, Opacity and Transmission channels.
Texture: With this option you can define a texture on the diffuse channel. These textures can be any of the image or procedural texture types. We will not go into the details here because we will describe the texture types of Octane in the relevant section. However, if you define the texture here, both the RGB and Float values are disabled. You just see the texture. If you want to see a mixture of both texture and color, read the following mix option.
Mix: With this option you can mix both the RGB color and the texture type. Diffuse color is the value you assign to zero, and 1 indicates texture color (or texture type) you assign. Values between 0 and 1 mix these two. The picture below shows exactly the situation.
These 4 options (Color, Float, Texture and Mix) that we talked about here are also used in other material types of Octane. In the following explanations, we will no longer explain what these four options are for. You can look at this section when you need it.
The roughness parameter controls the distribution of the specular highlight on the surface. Higher values are specular highlight sharp, lower values are milder. We will see this phenomenon better in the glossy material section. For example, in a glossy material, the roughness value also blurs the reflection. This parameter works entirely on the grey scale value. In this case, you can only enter the float value instead of the RGB values. The other options and how they work are the same as we talk about in the Diffuse channel. As a final note, depending on the material you will create, it will be your benefit to enter this value correctly. This depends entirely on what your purpose is. For example, if you are doing Motion Graphic, it may be a pleasant value. However, if you create real world material, the diffuse material alone and therefore the roughness parameter will not be enough. Keep this in mind.
With this parameter, you can create detailed indentations on the surface of the material you create. You can use any image or procedural texture, including greyscale. Bump map actually creates false roughened surfaces using texture on the surface. There is no change in the polygons of the object (you need to use displacement for it). For example, when the camera angle is parallel to the surface, the bump may lose its effect. In practice, it is important to use the bump (or normal / displacement) parameter in material creation because each surface is made up of small indentations. For the simplest use of the bump parameter, select image texture or octane procedural texture (eg noise) in the textures section. Then, if you are going to use image texture, load the image and select float from the options. Your use of Vram will be reduced when you choose this. Remember to use float in any situation where you need to use Greyscale image texture. All of these will be explained in more detail in the "Using Texture" section.
We can say that this parameter is more advanced than bump. The difference from Bump is the use of surface normals through the Red, Green, and Blue channels to create detailed indentations on the surface. To create a normal map you need to use software such as ZBrush, Mudbox, Bitmap2Material or Xnormal. In the Normal Map, there is also an intervention using only normals on the surface of the object. It does not change the topology of the object though.
Unlike Bump and Normal, this parameter changes the vertexes of your object using a greyscale image and creates a real surface based on the image you are using. For your Displacement Map to work well, your object must have a UV map. It is also very important that you have enough vertices / polygons of your object. The advantage of this parameter is that it creates extremely realistic surface indents. When you look at the camera from any angle, your surface will look detailed in every sense. Do not think of using Displacement just to create small indentations. For example, you can displace your object using a complexly shaped image of only black and white colors, and you can get rid of some modeling at this point. Unfortunately, every good thing has a price: Displacement is a process that requires a lot of computation and Vram. We recommend that you fully determine your purpose and use it. Displacement will be described in more detail in the chapter "Using Textures / Displacement".
info: Octane uses only greyscale images for displacement. There is also use of procedural textures with the help of Baking Texture feature. It will be explained in the textures section.
This parameter is for setting the transparency of your object. It uses only gray scale value. Black makes your object transparent. White makes it opaque. Between black and white, it becomes a semi-transparent image. So if you use the RGB channels, the colors outside the greyscale are insignificant. In this case, we recommend using Float value. Opacity channel is also open to creative use. For example, let's say you want to put a logo on a part of your object. In this case, after setting your diffuse color, if you put a logo with any alpha channel in the texture section of opacity, you will see the result in Lv. Do not forget to select "alpha" in the texture settings.
In this parameter, the Indirect Light photons in the scene react according to the color you define on the Transmission RGB channel. Outside of these, diffuse color is used. In other word, Diffuse RGB and Transmission RGB are mixed according to the Indirect Light. With this option you can create fake Subsurface Scattering. It's pretty fast in Render. However, creating a real subsurface Scattering is a very difficult process and it is not possible to produce with this parameter. You need to use the Medium parameter for this.
This parameter is used to convert any object in the scene to a light source. Also called Mesh Emitter. The use of this parameter is actually like simulating a similar phenomenon called "black body radiation". The black body is the electromagnetism which is released due to the temperature of the body. Each object emits electromagnetic radiation of certain frequency depending on its energy. This is what the emission material is supposed to simulate. In this way it is possible to turn any object in your scene into a light source. For more information about this parameter, please refer to "Octane Light Tag / Emission" section.
This parameter is used to create complex translucent materials. Such as wax, leather, skin, milk or leaf are created with this parameter. Also, the actual Subsurface Scattering effect we mentioned before in Transmission is also created using medium variants. This topic is also a complex one, you can find more detailed information in the "Mediums" section.
Shadow Catcher: With this option you can turn any object into a special object called "Shadow Catcher" in your scene. For example, let's say you have 2 objects in your scene. A and B objects. You want the A object to cast a shadow over the B object. In this case, create a diffuse material and tick the Matte option in the Common section. Then assign this material to the object you want to shadow. In Lv you will see that this object now only renders shadows. It is a very useful option. In some places you can get rid of render pass and compositing using this feature (not completely).
Smooth: The Smooth parameter is a Boolean (meaning that it is a toggle that turns the feature on or off) which smooths the transition between surface normals. If this option is disabled the edges between the polygons of the surface will be sharp giving the surface a faceted look.
Affect Alpha: When using specular material, you can use this option to show the refraction parts of your material as alpha. For example, you might want an HDR environment that you use in the refraction parts of your glass cup object to have a different look in compositing. Use this option in such cases. For this parameter to work, you have to activate "Alpha Channel" in Kernel settings.
Rounded Edges: The Rounded Edges parameter bevels the edges of the surface at render time automatically without the need to alter or subdivide the geometry. Using this option can enhance the realism of objects by eliminating overly sharp edges. The value refers to the radius of the rounded edge. Higher values for this setting produce rounder edges.
C4D Shaders: You can also adjust the Cinema 4D shader quality here. A detailed description of this topic can be found in this section.
Vertext Map Resolution: This parameter works internally. Default value is recommended.
We assume that you know this part because this parameter consist of the classic Cinema 4D's material editor options. If you want to learn the details, you can look at the corresponding section in the Help file of Cinema 4D.
If you click on it, you will be directed to the corresponding section of this Help file.
From here you can see which objects you have assigned to the material you created.