In order to understand Blackbody Emission, first we need to explain the natural phenomenon called "black body radiator". A "black body" is an electromagnetism that is released due to the temperature of the body. Each object emits electromagnetic radiation of certain frequency depending on its energy. The lowest temperature that can be present in the universe is 0 Kelvin (-273.15 Celcius).
All objects radiates warmer than 0 Kelvin. However, since the radiation is not in visible wavelength, we can not see those. As the temperature increases, it begins to emit visible light. It is a good example of the reddish black body composition that is emitted from the spaces between burning hot charcoal pieces. The color of the light depends on the temperature of the coal parts. Even you'll emit a black body, but not visible with naked eyes because it is not in the "visible wavelength".However you can be seen with thermal equipment as a blackbody radiator (as you see in Hollywood movies).
This natural phenomenon is simply formulated in the name of "Blackbody Emission" in Octane. This feature works in regular lights (Area, Targeted Area, IES light), and it is also possible to turn any object in your scene into a light source. From here you can set the temperature of the Kelvin by entering the temperature values (change in the color of visible wavelengths as the temperature increases or decreases). What matters here is not the object shape on scene, but the emission. In the example below, the light you see on the left is the Octane's default "Area light". The other three are the classic Cinema 4D objects. However, when we define "Blackbody Emission" for these objects, they will be "blackbody radiator" and begins to emit light like the default Octane Area Light. These objects are called "Mesh Emitters" in Terminology. Octane Area Light also uses Blackbody Emission by default and is written to create light in a practical way. That's how the Emission feature works in Octane.
How to setup a Blackbody Emission to any object
First create any object you want to be light, for example a disc object. You can set the disk object to the size you want. Then create a Diffuse material and assign this material to the Disc object. Now open the Node editor and drag and drop the Diffuse material you created in the Node editor. Then select "Blackbody Emission" from the "Texture Nodes" menu on the left side of the Node editor and connect it to the "Emission" slot of the diffuse material (setup shown below). That's it. By selecting the blackbody emission node, you can adjust your light settings in the settings window that appears on the right. These light settings are the global settings of the blackbody emission. In the "Octane Light Tag" section we will describe these settings in detail. As you can see, setup is quite simple and you can use it to make "Mesh Emitter" easily.