Unity Package for MDAL

The Mesh Data Abstraction Layer (MDAL) is a C++ library for handling unstructured mesh data released with MIT license. It provides a single data model for multiple supported data formats. MDAL is used by QGIS for data access for mesh layers.

MDAL is from the same "stable" of DALs as GDAL and has a dependency upon GDAL.

This repo is a Unity Package for using MDAL in a project.

This Package is part of the ViRGiS project - bringing GiS to VR.

Installation

The Package can be installed from Open UPM. If you use this method, the dependencies will be automatically loaded provided the relevant scoped registry is included in your project's manifest.json :

scopedRegistries": [
    {
      "name": "package.openupm.com",
      "url": "https://package.openupm.com",
      "scopes": [
        "com.openupm",
        "com.virgis.geometry3sharp",
        "com.virgis.conda-extensions"
      ]
    }
  ],

The Package can also be installed using the Unity Package Manager directly from the GitHub Repo.

The UPM package is based on the Conda package which has dependencies on other Conda packages but that is not apparent to the user.

Version numbers

This package is a wrapper around a C++ library. We want to keep the link to the library version. However, we also need to be able to have multiple builds of the package for the same underlying library version. Unfortunately, UPM does not have the concept of a build number.

Therefore, this package uses the version numbering proposed by Favo Yang to solve this. This adds two digits for build number to the SemVer patch value i.e. 3.1.1 => 3.1.100, 3.1.101, 3.1..102 etc.

This has the unfortunate side effect that 3.1.001 will revert to 3.1.1 and this means :

Package	Library
3.1.0	3.1.0
3.1.1	3.1.0
3.1.100	3.1.1.

Development and Use in the player

NOTE For the avoidance of doubt, conda is NOT required on machines running the distributed Unity application. The required libraries are automatically included in the distribution package created by Unity.

The scripts for accessing MDAL data are included in the Mdalnamespace and follow the MDAL C Api.

For more details - see the documentation.

The MDAL library is loaded as an unmanaged native plugin. This plugin will load correctly in the player when built. See below for a note about use in the Editor.

This Library works on Windows, Mac and Linux platforms.

Running in the Editor

This package uses Conda to download the latest version of GDAL.

NOTE - When installing Miniconda on Windows, you should select the option to add to the Windows Path. This is not the preferred option but IS required for this package to work.

For this package to work, the development machine MUST have a working copy of Conda (either full Conda or Miniconda) installed and in the path. The following CLI command should work without change or embellishment:

conda info

If the development machine is running Windows, it must also have a reasonably up-to-date version of Powershell installed.

NOTE - recent versions of Miniconda for Windows by default create a "Conda Shell" for running conda commands and have not included the conda executables in the general Windows path. For this package to work, the command listed above MUST work in the general Command Prompt and thus conda must be in the path. If the path entry is not created during the Miniconda install, this usually (if Miniconda was installed for one user only) means that the following must be added to the path environment variable in Control Panel: %USERPROFILE%\miniconda3\condabin. If Miniconda was installed for All Users, the actual path will be different and this entry should be updated accordingly

The package will keep the installation of GDAL in Assets\Conda. You may want to exclude this folder from source control.

Documentation

See the API Documentation.

A typical sample program :

using Mdal;
using g3;

  List<DMehs3> features = new List<DMesh3>();

  // for MDAL files - load the mesh directly
  ds = Datasource.Load("...SourceFileName");

  for (int i = 0; i < ds.meshes.Length; i++) {
      DMesh3 mesh = ds.GetMesh(i);
      mesh.RemoveMetadata("properties");
      mesh.AttachMetadata("properties", new Dictionary<string, object>{
      { "Name", ds.meshes[i] }
  });
      // set the CRS based on what is known
      if (proj != null) {
          mesh.RemoveMetadata("CRS");
          mesh.AttachMetadata("CRS", proj);
      }
      if (layer.ContainsKey("Crs") && layer.Crs != null) {
          mesh.RemoveMetadata("CRS");
          mesh.AttachMetadata("CRS", layer.Crs);
      };
      features.Add(mesh);
  }

Use with Unity Cloud Build

As of release 1.0.1, this package will work with Unity Cloud Build.

You will need to add a pre-build script to your build configuration in Unity Cloud Build to load Miniconda.

For Windows configurations - the following script works well:

https://gist.github.com/nimaid/a7d6d793f2eba4020135208a57f5c532

For Macos and Linux, something like this:

echo starting conda install

curl https://repo.anaconda.com/miniconda/Miniconda3-latest-MacOSX-x86_64.sh -o conda.sh
bash conda.sh -b -p ~/local/miniconda3
echo completed conda install