Entity types

A bimtex file is a flat list. Every line is one JSON object, and the object's t says what it is. There is no nesting, no document tree, no opening and closing of anything.

{"t":"level","id":"g","name":"Ground","elev":0,"height":3}
{"t":"room","id":"kitchen","label":"Kitchen","level":"g","x":0.3,"y":0.3,"w":4,"d":3}

Structure comes from ids. The room says "level":"g" and that is the entire mechanism — the same one that puts an opening in a wall, a roof on a storey and a canopy on a parapet. References are always ids and never array positions, so reordering the file changes nothing.

What you have to know before the table

Three conventions, and then the reference below answers everything else.

Units are metres, always. "w":4 is four metres. There is no unit field on an entity; project.unit records what the drawing is dimensioned in, not what the numbers mean.

Axes are x east, y south, z up. So a bigger y is further down the plan, which matches how you read a drawing and surprises people who expect graph paper.

Ids are yours and they are permanent handles. Name them the way you would name a room on a real drawing — kitchen, w-south, roof-main — because every diagnostic you ever read will quote them back at you.

Where to go next