Not so much a question as an answer I hope. Scroll down to the bottom if you want to get to the important bit about how to do it. Very slowly I am putting together a BJS Guide as a companion to the official documentation and working on materials I came across reflectionTextures and MirrorTextures.and got well lost. With some help from @Deltakosh I sort of got it for coordinatesMode and started on mirrors and couldn't make them work. So after a search or two I found @Luaacro 's bo