workaround for display issue 'burning-through'

Sometimes in Google Earth (as well as in Sketchup), semitransparent parts of png-textures look very strange. Instead of the faces behind the png, you see the Google Earth terrain in the background. The png texture 'burns through' all faces.

This can not be fixed by using pngs with only fully or zero transparent pixels, because in GE, pngs are sampled with something like a bilinear filter which always calculates a semitransparent transition between fully transparent and opaque pixels.

When I modelled the European Parliament, I got such an ugly result that I could never ever upload to the 3d-warehouse. More than half of it was burned through and I could see the Google Earth terrain well:

I found out (by chance!) that I need to put all faces behind the pngs in one group (so that all pngs are outside of this group). PNGs seem only to burn through faces that are on the same level in model hierarchy, they do not burn through groups or components.