Emission strength was finally added to the principled BSDF node in both Cycles and EEVEE, resolving a small but potent paper cut.
https://twitter.com/cgonfire/status/1306934530104856583
Previously, the principled BSDF node only had an emission color attribute. This forced the user to use workarounds in order to control the emission strength via the sole “emission color” socket. This new feature allows controlling the emission strength more intuitively by exposing an "emission strength" socket.
Alex Strand authored this patch, through which he did some work under the hood in order to make this fix work. Some of the changes he made include removing the hardcoded strength from the Cycles implementation and replacing it with the shader input, and updating the Eevee GLSL code to include an emission strength multiplier.
He is also currently working on updating the DAE, FBX and OBJ importers and exporters to support this change in the principled BSDF node.
This feature has already landed in master, and you can try it out in the latest Blender 2.91 experimental build!
