Sometime it is necessary to make some areas of a model emit light. For example, we might have a TV screen that needs to glow in the dark.
Reality makes this taks very easy. If we click on the Modifiers tab of any material, we find, at the bottom of the panel, the Light emission modifier, which is enabled by a checkbox:
Enable that option and the material will start emitting light. It’s that simple. Now, if we look at the Light emission panel, we can see that there is room for a texture to be used for the light emission. By default, the light emitted by the material is simply white light. If we want to use the same colors that are used in the Diffuse channel, the channel that gives the surface color, we can achieve that effect by simply linking to the Diffuse texture. This is done by clicking on the gear menu next to the texture and by selecting “Use Existing.” This option allows us to use and existing texture for the channel. When we select it, a window opens showing us the list of available texture for the material, and their role. For example, Diffuse, Bump, or Specular.
So, we can simply select the Diffuse texture and then light emitted will have the colors of the surface.
Now, when people use this option, they generally expect some sort of glow. That is not how light behaves in he real world. Light sabers, if they really existed, would probably look almost completely white. A light emission device, when look straight in front, looks white, especially if photographed. Cameras have much less latitude of the human eye. Light sabers, or many other glowing effects in movies, are created artificially, using digital manipulation and tracking of otherwise dull objects. Since we use a physics-based renderer (PBR), the effect returned is consistent with the laws of Nature and not Hollywood’s 😉
I have prepared a short video tutorial that shows how to make materials emit light. You can find it at out YouTube channel:
Stay tuned for more tips next week.