IDTF
From Just Solve the File Format Problem
IDTF (Intermediate Data Text Format), not to be confused with Intermediate Data Format (a format used for representing electronic circuit designs), is a format for 3D models. As its name implies, it's a text-based format which is used as an intermediate form during data conversions from one format to another. For instance, converting from PLY to U3D format can go through this format.
Links
- Interactive 3D brains in PDF documents (describes a conversion process)