FlatBackgroundGUI provides a background that is loaded from a PNG or JPEG image. The string for backgroundPath should be in "stringImportPaths" specified in dub.json
A destructor is present on this object, but not explicitly documented in the source.
Fill diffuse map with diffuse from background image. Alpha is ignored since ideally a background image will not need an alpha channel. Material and depth maps are zeroed out to initialize them. Otherwise this can lead to nasty errors.