I just came across a blog post by archivist Andrew Berger about a cache of stereoscopic photos of WWI at the Sterling Memorial Library, Yale University. Stereoscopic photography, like our eyes, uses two lenses in parallax to create a pair of simultanous, side-by-side images of a subject, which are then viewed in a stereograph device to create a single image with a 3D effect. The format dates back to photography's beginnings during the 19th Century. I believe TU has some stereoscopic photos of WWI, if anyone cares to research them.