mm2txt and mm2ply now have a --export-fields flag

apps/mm2ply/README.md

@@ -9,6 +9,7 @@ A command-line tool to export the layers of a MOLA metric map (*.mm) file as PLY
 ## Features
 
 - Exports all point cloud layers from a metric map file
+- Selectively exports specific fields in a custom order
 - Supports both ASCII and binary PLY formats
 - Preserves all point fields (coordinates, colors, intensities, etc.)
 - Automatic field name mapping for standard color attributes
@@ -21,14 +22,15 @@ This tool is built as part of the MOLA framework. Please refer to the [MOLA docu
 ## Usage
 
 ```bash
-mm2ply -i <input.mm> [-o <output_prefix>] [-b]
+mm2ply -i <input.mm> [-o <output_prefix>] [-b] [--export-fields <field1,field2,...>]
 ```
 
 ### Arguments
 
 - `-i, --input <file.mm>` (required): Input metric map file
 - `-o, --output <prefix>` (optional): Prefix for output PLY files. If not specified, uses the input filename without extension
 - `-b, --binary` (optional): Export in binary format instead of ASCII (default: ASCII)
+- `--export-fields <field1,field2,...>` (optional): Comma-separated list of fields to export in the specified order. If not provided, all available fields will be exported. Spaces around commas are allowed
 
 ### Examples
 
@@ -50,6 +52,24 @@ Export in binary format for smaller file sizes:
 mm2ply -i mymap.mm -b
 ```
 
+Export only specific fields in a custom order:
+
+```bash
+mm2ply -i mymap.mm --export-fields "x,y,z,intensity"
+```
+
+Export selected fields in binary format:
+
+```bash
+mm2ply -i mymap.mm -b --export-fields "x, y, z, color_r, color_g, color_b"
+```
+
+Export only 2D coordinates and intensity:
+
+```bash
+mm2ply -i mymap.mm --export-fields "x,y,intensity"
+```
+
 ## Output
 
 The tool creates separate PLY files for each point cloud layer in the metric map. Files are named using the pattern:
@@ -62,14 +82,26 @@ For example, if your map contains layers named "raw" and "filtered", you'll get:
 - `mymap_raw.ply`
 - `mymap_filtered.ply`
 
+## Field Selection
+
+When using the `--export-fields` option:
+
+- Fields must be specified as a comma-separated list
+- Spaces around commas are allowed (e.g., `"x, y, z"` or `"x,y,z"`)
+- Fields will be exported in the exact order specified
+- All specified fields must exist in the point cloud, or an error will be raised
+- The tool validates field availability and reports available fields if a requested field is not found
+- Color fields (`color_r`, `color_g`, `color_b`) are automatically mapped to PLY standard names (`red`, `green`, `blue`) in the output file
+
 ## Supported Point Fields
 
 The tool automatically exports all point attributes, including:
 
 - **Coordinates**: x, y, z (float)
 - **Colors**: Automatically maps `color_r/color_rf` → `red`, `color_g/color_gf` → `green`, `color_b/color_bf` → `blue`
-- **Custom float fields**: Exported as float properties
-- **Custom double fields**: Exported as double properties
-- **Custom uint16 fields**: Exported as ushort properties
-- **Custom uint8 fields**: Exported as uchar properties
+- **Custom float fields**: Exported as float properties (e.g., intensity, normals, curvature)
+- **Custom double fields**: Exported as double properties (e.g., time, timestamps) (MRPT ≥ 2.15.3)
+- **Custom uint16 fields**: Exported as ushort properties (e.g., ring, color channels) (MRPT ≥ 2.15.3)
+- **Custom uint8 fields**: Exported as uchar properties (MRPT ≥ 2.15.3)
 
+The specific fields exported depend on the point cloud type in each layer. Use `--export-fields` to select only the fields you need.