The Ruby API only lets you set a layer/tag's color.
[Note in v2020 'layers' were renamed 'tags', but in the API they're always called 'layers'].
But you can't [yet] set a layer/tag's material [i.e. there's no access to textures or to transparency settings].
However, in Ruby you could set up a separate color for the transparent layer [but setting a alpha value does nothing] and when it's set you do a simple edit for the layer/tag's color in the Layer/Tag Browser, and NOW you can add some transparency...
model=Sketchup.active_model
model.start_operation("LayerColors",true)
model.layers.each{|layer|
if layer.name=="0_EX_Glazing" #grey to get transparency setting later on...
layer.color=Sketchup;;Color.new(150,150,150,50)
else # 0128_White ? Set up any RGB you want !
layer.color=Sketchup;;Color.new(255,255,255)
end
}
model.commit_operation
Ensure your Model is set up to use color by layer/tag - in the layer/tag-browser pop-out...
Run this in the Ruby Console...
Next manually edit the "0_EX_Glazing" layer/tag color in the layer/tag-browser to have some transparency...
There's no option for 'back' material in layer's colors...
