Point clouds of Blickfeld devices are usually recorded in the Blickfeld Point Cloud format with the extension .bfpc. It is based on Protobuf and contains all available meta information, e.g. the used scan pattern or firmware versions, and all additional information per point, e.g. the timestamp in nanoseconds or the scanline ID. The lossless format and the simple Protobuf extensibility with upcoming software upgrades are the main reasons why the custom format was developed and why it is recommended for raw recordings. The dumped recordings can be easily converted with the Blickfeld Recorder to common point cloud formats.
A point cloud dump is structured into three blocks: First the Header message, then a repeating Data block with encapsulated Frame messages, and finally a Data block with an encapsulated Footer message. All blocks are prefixed with a variable unsigned integer field (unsigned, 32 bit version of protobuf Varint type), which states the length of the consequent Protobuf encoded message. The files are stored with GZIP compression to reduce the structure overhead of Protobuf.
The Header contains basic information about the device (e.g. serial number, timestamp, firmware version, etc.) and the recording client (e.g., library version, timestamp, etc.). The Header Protobuf definition can be found at PointCloud.Header.
The Data block contains either a Point Cloud Frame or the Footer, which ends the file. The Point Cloud Frame is also stored as a Protobuf message, which is defined at Frame. The Footer contains further metadata about the recording, which includes statistics, e.g., the total number of frames and points, and configuration events, e.g., active scan patterns in the recording. The Footer Protobuf definition can be found at PointCloud.Footer.
The combination of Header and Footer is referred to as Metadata in the library methods. The Metadata is automatically extracted when loading the Blickfeld Point Cloud recordings and can be used to inspect recordings without parsing all frames in the file.
Expected data sizes
Measurements and expected data sizes will be available soon.