Thanks for your replies guys!
I thought about the editing thing or more simply edit the .mtl file of the OBJ. But this adds another per-asset step that I want to avoid. And I don't really like scripting
Actually the reason I want to do that is mainly because I'm lazy: ideally I would have created a set of shaders for every type of material used, regardless of the assets. All the buildings for examples would have all the same shaders, and by just automatically picking up their correct texture, they would have their correct materials. (as I am creating different IDs texture for each buildings to define where each material should be applied).
This is of course the typicall "in a perfect world" situation, and the differences in the textures and colors of each assets already tells me that I will need to do little adjustments to each one of them.
I tried having the textures in the asset folder and it works like a charm! From what I understand it is still looking up the filename of the OBJ defined by the .mtl file, but Terragen is able to look up for this relative texture path, which is very handy. Unfortunatly I won't use it as I have some shared texture between assets like trees, and this would mean unnecessary texture duplicates.
Thanks for this and the precisions about the renderer Matt. I will keep each assets with its own set of shaders. It makes more sens anyway, and I will be able to export a tgo file for each asset that will be ready to render for any other scenes.
I am not worried about the UI thing, as all the shaders are inside the actual object nodes so I never have more that 20-30 nodes on the screen at the same time.
One last thing:
In the default shader, let's say you put the same file in two slots. For example a .PNG file with alpha.
You put the filepath in the Color section and the same path in the Opacity section with "use alpha as opacity".
Would the shader be smart enough to load the texture one time or would it load the file two times?
Also, it seems that it is automatically applying a linear gamma to the color file, which is correct. What about the displacement and specular slots? Is it leaving the gamma as is (no gamma correction)?
I am used to change that manually in the Image Map shader, but I am curious about what's happening under the hood of the default shader.
Thanks again!