I can usually create textures for OBJ files, either by applying a single-colored file or by first using UV Maker, but occasionally I come across downloads that refuse to accept textures, i.e. no pattern shows up on my monitor either before or after rendering. Strangely, some objects do accept a plain-colored, square JPG file, but not a patterned one. How can this be, and how can I effectively texture such illusive objects?