Another option is to use .onBeforeCompile() to modify shaders of built-in materials, using gl_FrontFacing, THREE.DoubleSide and a buffer attribute for the additional set of UV coordinates for back faces of THREE.PlaneBufferGeometry().

Another option is to use .onBeforeCompile() to modify shaders of built-in materials, using gl_FrontFacing, THREE.DoubleSide and a buffer attribute for the additional set of UV coordinates for back faces of THREE.PlaneBufferGeometry().
