ldt EULUMDAT File FormatDocumentation by Paul Bourke
The following describes the ldt or EULUMDAT File Format for describing 3D Luminaire distributions. It is a purely text format. The original specification has quite tight regulations on the allowed lengths of each line which is generally more relaxed in modern practice.
Here is a sample ldt file. Noting that since they are purely text they can be opened in any text editor or word processor. The 3D geometry is this file looks like the following OBJ file, or rendernig below.