# Importing Point Clouds

## How to import

Open a point cloud file using one of these methods:

- **Menu**: Point Cloud > Import...
- **Ribbon**: Point Cloud tab > Import button

A standard file dialog appears. Select one or more files in any supported format. TunnelCAD reads the raw data, converts it to its internal IQPC format, and displays the result on the Point Cloud canvas tab.

## Format details

### LAS / LAZ

LAS is the industry-standard binary format for LIDAR point cloud data, defined by the ASPRS (American Society for Photogrammetry and Remote Sensing). It stores point coordinates, intensity, classification, RGB color, and return information.

LAZ is the compressed variant of LAS, typically 5--10x smaller on disk. TunnelCAD uses the **liblaszip** library to decompress LAZ files transparently during import.

### E57

E57 is the ASTM E2807 standard for storing 3D imaging data from laser scanners, structured-light systems, and other 3D measurement devices. It supports multiple scans in a single file, point coordinates, color, intensity, and scanner metadata.

TunnelCAD uses the **libE57CWrapper** library to read E57 files.

### PLY

PLY (Polygon File Format, also known as Stanford Triangle Format) is a simple format for storing 3D vertex data. TunnelCAD reads the vertex positions and optional RGB color attributes. Both ASCII and binary PLY variants are supported.

### PTS

PTS is a text-based point cloud format commonly exported from Leica scanners. Each line contains space-separated values:

```
X Y Z Intensity R G B
```

Intensity is a reflectance value. R, G, B are 0--255 color components.

### XYZ

XYZ is the simplest text-based format. Each line contains space-separated coordinates:

```
X Y Z
```

Some XYZ files include additional columns for RGB color (X Y Z R G B). TunnelCAD auto-detects the column count.

## Import behavior

- The import process runs in a background thread with a progress indicator. Large files (tens of millions of points) may take several seconds to load.
- Once imported, the point cloud is cached as an **IQPC** file alongside the project. On the next session, TunnelCAD reloads the cached IQPC file instead of re-parsing the raw format.
- The point cloud appears immediately on the **Point Cloud** canvas tab after import.
- Multiple point clouds can be loaded simultaneously (e.g., separate scans of different tunnel sections).

## Removing point clouds

To remove a loaded point cloud from the project:

- **Menu**: Point Cloud > Clear

This unloads all point cloud data from memory. The cached IQPC files remain on disk and can be reattached later.

## Working with large datasets

TunnelCAD supports point clouds with millions of points. The Point Cloud canvas uses **Level of Detail (LOD)** rendering -- when zoomed out, a subset of points is displayed for smooth navigation; as you zoom in, progressively more detail is shown. The full dataset is always available for section extraction regardless of the current LOD level.

```{tip}
For very large scan datasets (100M+ points), consider splitting the data into per-station or per-zone files in your scanning software before importing. This lets you load only the relevant portion when working on a specific section of the tunnel.
```