Spec Writing Guide

[pjcozzi]

As we add more tile formats, 3D Tiles needs to stay consistent.

Terminology

• Tiles are composed of sections such as header and body. Sections are composed of fields such as magic and version.
• "Feature" - indicates one model in a batch of models (b3dm), one instance in a collection of instances (i3dm), one point in a point cloud (pnts), one polygon in a vector tile (vctr), etc.

Fields

• field names are in camelCase.
• Length - a Length suffix on a field name indicates the number of elements in an array.
• ByteLength - a ByteLength suffix indicates the number of bytes, not to be confused with just Length.

Header

• Each tile format starts with a header that starts with the following fields:

magic            // uchar[4], indicates the tile format
version          // uint32,   1
byteLength       // uint32,   length, in bytes, of the entire tile.

Binary

• All binary data, e.g., tile formats, are in little endian.

This is a work-in-progress. There are more guidelines to come.