A DMM is 1 millimeter viewed at 1 meter away. It’s an angular unit that follows a MM into the distance.
“I recently watched a great talk by the Google Daydream team about designing screen interfaces for VR. Adam Glazier and Chris McKenzie dove into some of the challenges and pitfalls around creating two-dimensional screens within the VR space. Their team needed a way to design screens that could be easily read at any distance. To help solve this, they came up with “Distance-Independent Millimeters” or DMMs. The following are my summarized notes from their presentation at Google I/O 2017.”