Point Cloud File I/O

Point Cloud File I/O

Read and write 3-D point cloud data in MATLAB using Lidar Toolbox file I/O functions, covering PLY, PCD, LAS/LAZ, sensor PCAP, E57, and IDC (Ibeo) formats.

When to Use

• Loading a point cloud file from disk into a pointCloud object
• Saving a pointCloud object to disk in any supported format
• Deciding which reader or writer function to use for a given file format
• Reading LAS/LAZ files with selective filtering (ROI, classification, GPS time)
• Extracting or preserving lidar point attributes (classification, GPS timestamps, scan angle)
• Reading Velodyne, Ouster, or Hesai PCAP sensor recordings frame-by-frame
• Reading multi-scan E57 files with indexed access
• Reading Ibeo IDC sensor recordings with message-based access
• Converting between point cloud formats (e.g., LAS to PLY, PCD to LAZ)

When NOT to Use

• Streaming live sensor data in real time (use velodynelidar, ousterlidar, sicklidar)
• Processing or filtering point clouds after reading (use pcdownsample, pcdenoise)
• Reading or writing surface meshes (use readSurfaceMesh, writeSurfaceMesh)
• Saving point cloud variables to MAT-files (use save)
• Visualizing point clouds (use pcshow, pcplayer, pcviewer)

Must-Follow Rules

1. Route by file extension, not by habit — pcread ONLY supports .ply and .pcd files. For .las/.laz use lasFileReader + readPointCloud. For .pcap use the sensor-specific file reader (velodyneFileReader, ousterFileReader, or hesaiFileReader). For .e57 use e57FileReader. Calling pcread on a LAS or PCAP file produces an error, not a warning. Similarly, pcwrite ONLY writes PLY and PCD — for LAS/LAZ output use lasFileWriter + writePointCloud.

2. PCAP file readers require a mandatory device identifier — never guess it — velodyneFileReader requires a DeviceModel string (e.g., "HDL32E"). hesaiFileReader requires a DeviceModel string (e.g., "PandarXT32"). ousterFileReader requires a CalibrationFile path (JSON). If the user has not specified the device model or calibration file, ASK — do not assume a default. There is no default value; omitting it causes an error.

3. Use two-output syntax to get point attributes from LAS/LAZ — [ptCloud, ptAttributes] = readPointCloud(reader) returns a lidarPointAttributes object containing Classification, GPSTimeStamp, LaserReturn, NumReturns, ScanAngle, and more. The single-output form discards these attributes permanently. Intensity is on the pointCloud object (.Intensity property), NOT on lidarPointAttributes.

4. Preserve attributes with three-argument writePointCloud — writePointCloud(writer, ptCloud, ptAttributes) preserves Classification, GPSTimeStamp, and other lidar attributes in LAS/LAZ output. The two-argument form writePointCloud(writer, ptCloud) discards all attributes. If the user has attributes from lasFileReader/readPointCloud, always pass them through.

5. PLY only supports ascii and binary encoding — Calling pcwrite(ptCloud, "file.ply", Encoding="compressed") throws an error. Only "ascii" and "binary" are valid for PLY. The "compressed" encoding is exclusive to PCD format. Defaults (R2026a+): PLY="binary", PCD="compressed".

6. Always use string syntax — Use double-quoted strings ("text") for all literal text arguments (filenames, device models, encoding values, Name=Value values). Use Name=Value syntax for all name-value pairs. Never use character vectors ('text') or legacy 'Name','Value' pair syntax.

Preflight Procedure