LDraw

LDraw is an open text standard for describing LEGO brick models. It describes the construction structure piece by piece through part numbers, position coordinates, rotation, and color information. The file extensions are .ldr or .mpd, and the part library is maintained by the LDraw community.

LDraw is intended for assembly instructions and rendering: it records part assembly logic rather than a continuous mesh, so direct use for 3D printing requires first merging into a solid mesh. Model quality depends on the part library version and the renderer used. Part seams are merged during conversion.