LDraw

LDraw is an open text standard for describing LEGO brick models, specifying each piece through part numbers, position coordinates, rotation, and color information to represent the assembly structure. Files use the .ldr or .mpd extension, and the part library is maintained by the LDraw community.

LDraw is oriented toward assembly diagrams and rendering: it records the logical assembly of parts rather than a continuous mesh, so direct use for 3D printing requires merging into a solid mesh first. Model quality depends on the part library version and the renderer used; seams between parts are merged during conversion.