# Python Users: HOOPS Envision for Python

## Setting up the Environment

### Prerequisites

You will need Python to be installed on your system. Version 3.7 to 3.11 are supported. There is a version for each of these python packages. You will also need to install the requests module, eg. pip install requests. On Windows you will also need Visual C++ runtimes (see Deployment section below) which are usually already installed.

### License

To use HOOPS Envision for Python you will need a license. You can generate your license on https://developer.techsoft3d.com/ or by contacting support@techsoft3d.com. When you receive your license, please update the license string in the cee_envision/hoops_license.py file.

You can also do initialization of HOOPS Envision for Python manually and provide you license to the cee_envision.core.CoreComponent.initialize method. See Examples/minimal_core.py for an example on how to do this.

    from cee_envision import core
    comp_instance = core.CoreComponent.initialize(my_license_string)

### Configure your Installation

The only thing you need to configure to run the examples is the license as described above.

The examples scripts use the helpers/setup_environment.py to configure the PYTHONPATH and on Windows the PATH. You can choose to use this helper or in any other way setup the PYTHONPATH (and optionally PATH) for HOOPS Envision for Python to work. PYTHONPATH should point to the root of the HOOPS Envision for Python installation.

## Example Scripts

Minimal Test Example

This example creates a simple geometry with the cee_envision.geo module and exports the model to a PNG image. Run this to verify that the HOOPS Envision for Python installation is ok and that the off-screen rendering using OSMesa works as expected. The script will create an image called script_outputs/minimalImage.png

To run the example:

- go to the ./Examples folder

- using the terminal do:

      python minimal_osmesa.py

Tutorial

This example shows how to use HOOPS Envision for Python to extract information from the CAE file. It is also an introduction to the CAE object model of HOOPS Envision for Python.

To run the example:

- go to the ./Examples folder

- using the terminal do:

      python tutorial.py

Run the Export Examples

The Export Examples is a collection of examples showing how to use HOOPS Envision for Python to export to the Envision free viewers using VTFx, export to a cloud streaming database (CUG) and upload to Ceetron Cloud for remote visualization in a browser.

To run the example:

- go to the ./Examples/ExportExamples folder

- using the terminal do:

      python test-examples.py

If all works well, this will run a number of tests on provided example models located in ./Examples/DemoFiles: Ansys, Fluent, openFOAM and VTK-VTM

Tested functions, all with custom display model configuration:

- Export to CUG
- Export to VTFx
- Send model to Ceetron Cloud account
- Addition of a custom result to example Ansys model
- Export of the example Ansys model to a custom format, producing myFile.txt which is opened automatically

All result output is stored in “example_test_results” which can be deleted afterwards.

Take a Look at custom_vtfx_export.py

The other custom modules (custom_cug_export and custom_send_to_cloud) follow the same pattern: arguments are parsed and verified. A model is then opened, configured and exported to a VTFx file, or CUG folder or sent to cloud.

Note that the configuration of the model is passed as an argument : the user specifies the name of the configuration function and its parameters. For example, the following command line calls the configuration function “setLastStateAndScalar” with parameter “XX Stress*”

    python custom_vtfx_export.py ../DemoFiles/example_ansys.rst example_ansys_xx_stress.vtfx setLastStateAndScalar "XX Stress*"

The same can be achieved within a Python file:

    import custom_vtx_export
    custom_vtfx_export.run("../DemoFiles/example_ansys.rst", "example_test_results/example_ansys_xx_stress.vtfx", "setLastStateAndScalar", "XX Stress*")

Please note that if multiple files need to be opened to get a full model, they need to be specified as the first argument using a “,” as a separator. For example, this command line operates on a Fluent model using two files: example_fluent.cas (geometry) and example_fluent.dat (results)

    custom_vtfx_export.run("../DemoFiles/example_fluent.cas,../DemoFiles/example_fluent.dat",   "example_test_results/example_fluent_all_velocity.vtfx",    "setLastStateAndScalar",    "All Vel*")

Use for Your Own Needs

The customizable part of all these export and shares (VTFx, CUG, SendToCloud) is thus isolated as a configuration function in the configure model. This is where you would write your own display model configuration functions, which can then be invoked by name on the command line as seen above. The functions rely on HOOPS Envision programming, please refer to the documentation or contact Tech Soft 3D for an introductory training to get you up to speed.

## Documentation

HOOPS Envision for Python offers all of the features from HOOPS Envision for Desktop. HOOPS Envision for Desktop is written in C++ and HOOPS Envision for Python is provided as a wrapper layer on top of this. Because of this, all documentation and tutorial snippets are provided in C++ only. However, we believe that reading class/function descriptions and code examples in the C++ generated documentation will be straightforward for a Python programmer.

The Python wrapping targets Python 3.7 to Python 3.11.

You may wish to consider using Anaconda, which is a friendly Python distribution including a large variety of packages used in the engineering community.

### Modules

HOOPS Envision for Python is provided as a Python module named cee, which contains one submodule per C++ namespace.

Python module | HOOPS Envision | C++ namespace
cee_envision.core | CeeCore | cee
cee_envision.vis | CeeVisualization | cee::vis
cee_envision.geo | CeeGeometry | cee::geo
cee_envision.ug | CeeUnstructGrid | cee::ug
cee_envision.plt | CeePlot2d | cee::plt
cee_envision.rep | CeeReport | cee::rep
cee_envision.exp | CeeExport | cee::exp
cee_envision.imp | CeeImportCae | cee::imp
cee_envision.osmesa | CeeOSMesa | cee::osmesa
cee_envision.vtfx | CeeVTFx | cee::vtfx

## Getting Started with HOOPS Envision for Python

Once the python components are all set you can verify your installation by launching the script minimal_osmesa.py within the Examples/ folder. The documentation for each C++ namespace translated into Python modules are found in the main C++ documentation.

Please read a list of topics before starting. This will help you understand the main concepts of HOOPS Envision for Desktop, license, CloudIds and others (see Topics). The HOOPS Envision for Desktop components overview are found in Components Overview.

## From C++ Documentation to Actual Python Code

The C++ namespace are translated into Python Modules.

    # C++
    using namespace cee::app

    # Python
    import cee_envision.app

walking through the library

    # C++
    cee::Str fileName = "path/to/my/file";
    cee::ug::Error error;

    cee::ug::Model* model = cee::app::Models.open(filename,  &error);

    # Python
    from cee_envision.app import models
    fileName = "path/to/my/file"

    model = models.open(fileName)

Accessing methods by pointers in C++ become dot in Python.

For instance, the visibility for an object is typically accessed using visible()/setVisible() in C++.

    # C++
    # class cee::ug::PartSettings
    int partId = 1;
    size_t globalGeometryIndex = 1;
    cee::ug::PartSettings* settings = model->partSettings(globalGeometryIndex, partId);
    settings()->setVisible(false); // request to hide part on the view

    # Python
    partId = 1
    globalGeometryIndex = 1

    settings = model.partSettings(globalGeometryIndex, partId)
    settings.setVisible(False)

As you can see, the translation is very straight forward. Please check the tutorials in Tutorials and come back to this section to help you translate the C++ code into python.

### Inheritance

Due to limitations in the Python wrapper layer, there is a special handling of inheritance in the Python version of HOOPS Envision for Desktop. The problem is downcasting objects that are fetched from within HOOPS Envision for Desktop.

For instance:

    myGeo = GeometryModel()
    myView.addModel(myGeo)

    model = myView.model(0)                                    # Get myGeo as a Model from the cee_envision.vis.View instance.
    geometryModel = GeometryModel.castFromBaseClass(model)     # Cast to a GeometryModel using the provided method
    markupModel = MarkupModel.castFromBaseClass(model)         # This results in markupModel being None

In this scenario, in order to obtain an instance of GeometryModel when getting a Model from the view, we have provided casting methods for all such classes. Using the static castFromBaseClass will always give you a correct cast. For an invalid cast, the returned value will be null.

### Identity Operator

Due to the wrapping mechanism of underlying C++ objects, the Python “is” operator does not provide the expected behavior when objects are passed on to C++, for example to be stored in C++ pointer collections. In these cases, if identity needs to be tested, a specific operator named swigis has been implemented in the cee_envision.core module.

    ...

    from cee_envision.core import swigis

    ...

    resources = ImageResources()

    image1 = Image()
    res.addImageResource("image 1", image1) # object image1 will be stored in a C++ object collection

    image2 = res.imageResource("image 1") # retrieving the same object

    print(image2 is image1)         # unexpectedly False (Python objects wrapping the C++ are different)
    print(image2 |swigis| image1)   # allows to compare underlying C++ objects

## Deployment

For HOOPS Envision for Desktop, the development language is C++, which means that any product developed using one of our toolkits must are depending on Visual C++ redistributables. For more information on deployment of Visual C++ based applications, see Deployment in Visual C++

Using the redistributable packages is recommended because they enable automatic updates of the Visual C++ libraries. The latest Visual C++ Redistributable Packages for Visual Studio 2015-2022 can be downloaded using this permalink for the latest supported x64 version: https://aka.ms/vs/17/release/vc_redist.x64.exe

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