How do I get transparency to work with the Principled BSDF shader? How do I get the Cycles Principled BSDF shader to support a base color image such as a 32bit png with alpha or a tga with an alpha channel, and get the transparency to work. I don't see anywhere on the Principled BSDF shader that handles transparency.

Without success, I have tried:


Properties Editor>Render tab>Film rollout>Transparent
Properties Editor>Material tab>Settings rollout>Viewport Alpha (changing to other than Opaque).
Adding a Transparent BSDF and Diffuse BSDF after the base
color image node and using a Mix Shader to combine them.
The principled shader can be combined just like any other shader.
Adding a Transparent shader and using the alpha channel to control the mix will make the black sections of the Alpha become transparent.



Read also: 
Add a transparent image on top of a material