Whats the procedure for a Linear workflow in TG3?
Do you have to apply a gamma correction on the shaders? I assume you would need to on any SRGB texture files.
In all versions of Terragen 2 or 3, the Image Map Shader has a built-in "convert to linear" setting which defaults to gamma 2.2 (which is an approximation to sRGB). This assumes you are loading an sRGB texture and want a linear workflow. If your texture is linear (e.g. an EXR) then you should set "data is linear" or set the conversion gamma to 1.0.
In the professional version will the render view window display linear files?
Or will you need to save the Liner file out and view it in an external viewer that will convert it to SRGB?
In all versions of Terragen 2 or 3 the Render View uses whatever gamma is set in the "Effects" tab of the render node. It defaults to 2.2. The whole setup is designed for a linear workflow and display on a gamma 2.2 display by default. However, this display gamma is baked(*) into the 8-bit or 16-bit low-dynamic-range image which the Render View displays, so if you want to change the gamma you'd need to re-render, but if you want a linear workflow you shouldn't need to change the gamma. EXR output is *always* linear, and ignores the gamma on the render settings.
(*) We might be able to make this dynamic in future.
You might see differences between the Render View and an external EXR viewer because Terragen has some built-in tone mapping controls (on the "Effects" tab) which affect the low dynamic range image, but not the EXR. If you turn off "contrast" and "soft clip effect" it should be perfectly linear.
I hope that makes sense. Let me know if you'd like anything explained differently.