I have just submitted an update for my glTF exporter, in version 1.3.0 I have added the ability to overwrite the default material values specific to PBR.
Sketchup materials only support color, texture and transparency, so when rendered the models look flat and dull.
PBR means Physically Based Rendering, and it defines Metallic and Roughness factors for materials.
Metallic: A material can either be a non-metal (dielectric) or metal with full reflectance, or anything in between.
Roughness: A material can range from smooth (and glossy) to rough.
I have also added emissive control, and doubleSided override flags.
This is done by changing the name of the material such that it includes the following:
metallic=nnn, where nnn is in the range 0.0 to 1.0 (sorry, only eleven possible values at the moment, let me know if you need more flexibility).
roughness=nnn, where nnn is in the range 0.0 to 1.0
doubleSided=true or doubleSided=false
emissive=rrr,ggg,bbb where rrr,ggg,and bbb are in the range of 0.0 to 1.0
Emissive materials ‘glow’ with the color that you specify, so are great for car headlights, creepy glow-in-the-dark eyes, that sort of thing.
If, for example, you have gold in your model, you can change the name of the material from ‘gold’ to ‘gold metallic=1.0 roughness=0.0’
Please note: I have a default Metallic-factor of 0.1, and default Roughness-factor of 0.9 in the glTF exporter.
Here is the same model, exported with the default material name, and then exported with the extra definitions in the material name. You may spot a subtle difference.
Here is a 3D Warehouse model, in this case MJC’s model of a Cylon Raider from the 1970’s Movie and TV Series ‘Battlestar Galactica’
In the first instance, the model is exported ‘as is’, and in the second case it is exported with a metallic factor for the hull and emissive factor for the engine exhaust flame.
In this case I’ve changed the name of the hull material to ‘CylonRaider metallic=0.4 roughness=0.1’
You will notice that the second model has a more prominent engine exhaust, and better light reflections from its more metallic surface.
Let me know if you have any requests for the exporter!