Scene Importer & Exporter

The Simplygon API provides classes for loading and saving various scene file formats. Currently the supported format are

• Alembic (.abc)
• FBX (.fbx)
• glTF (.gltf, .glb)
• Houdini geometry (.bgeo)
• OBJ (.obj)
• Simplygon (.sg)
• USD (.usd, .usdc, .usda)

Importing

Importing scene data is done by the ISceneImporter class. The file information is then stored in an IScene, where both the geometries, materials and textures of the imported file can be found.

void LoadScene( const char* readFrom )
{
    spSceneImporter importer = sg->CreateSceneImporter();
    spScene scene;

    // Set the path of the file to load
    importer->SetImportFilePath( readFrom );
    if( importer->RunImport() )
    {
        scene = importer->GetScene();
    }
    // do stuff with scene
}

void LoadScene( string readFrom )
{
    spSceneImporter importer = sg.CreateSceneImporter();
    spScene scene;

    // Set the path of the file to load
    importer.SetImportFilePath( readFrom );
    if( importer.RunImport() )
    {   
        scene = importer.GetScene();
    }
    // do stuff with scene
}

def LoadScene( readFrom ):
    importer = sg.CreateSceneImporter()
    scene = None
	
	# Set the path of the file to load
    importer.SetImportFilePath( readFrom )
    if importer.RunImport():
        scene = importer.GetScene()
    # do stuff with scene

Exporting

Exporting scene data is done by the ISceneExporter class. The file format is determined by the file name extension.

If the file name does not contain a known supported file extension (see list above) it will output the internal Simplygon binary scene dump format (same as if you export a file with .sg extension), which can then be read by the scene importer. This is useful for integrating the batch tool into your data pipeline or when requesting support, as it contains an exact representation of the Simplygon scene data.

void SaveScene( const char* fileName, spScene scene )
{
    spSceneExporter exporter = sg->CreateSceneExporter();
    exporter->SetScene( scene );
    exporter->SetExportFilePath( fileName );
    
    // For file formats that only supports a limited set of texture coordinate layers,
    // set the name of the primary layer to export
    exporter->SetPrimaryTexCoordName( "tex0" );

    // Some file formats support embedding texture and other data in the main scene file.
    // This flag controls if such data will be embedded or written to separate files
    exporter->SetEmbedReferences( true );

    // Some file formats  support exporting cascaded scenes in the same file.
    // This flag controls if cascaded scenes will be written or ignored
    exporter->SetExportCascadedScenes( true );

    exporter->RunExport();
}

void SaveScene( string fileName, spScene scene )
{
    spSceneExporter exporter = sg.CreateSceneExporter();
    exporter.SetScene( scene );
    exporter.SetExportFilePath( fileName );
    
    // For file formats that only supports a limited set of texture coordinate layers,
    // set the name of the primary layer to export
    exporter.SetPrimaryTexCoordName( "tex0" );

    // Some file formats that support embedding texture and other data in the main scene
    // file, this flag controls if such data will be embedded or written to separate files
    exporter.SetEmbedReferences( true );

    // Some file formats  support exporting cascaded scenes in the same file.
    // This flag controls if cascaded scenes will be written or ignored
    exporter.SetExportCascadedScenes( true );

    exporter.RunExport();
}

def SaveScene( fileName, scene ):
{
    exporter = sg.CreateSceneExporter()
    exporter.SetScene( scene )
    exporter.SetExportFilePath( fileName )
    
    # For file formats that only supports a limited set of texture coordinate layers,
    # set the name of the primary layer to export
    exporter.SetPrimaryTexCoordName( "tex0" )

    # Some file formats that support embedding texture and other data in the main scene
    # file, this flag controls if such data will be embedded or written to separate files
    exporter.SetEmbedReferences( True )

    # Some file formats  support exporting cascaded scenes in the same file.
    # This flag controls if cascaded scenes will be written or ignored
    exporter.SetExportCascadedScenes( True );

    exporter.RunExport()
}

Cascaded scenes

You can output all cascaded scenes when exporting by setting the export cascaded scene flag with a call to SetExportCascadedScenes function. Note that all file format does not fully support cascaded scenes.

Format specific options

FBX

You can control the exported FBX file format version by setting a global string setting "FBXFileExportVersion". The values for the version strings are listed in the FBX SDK "File version compatibility strings", for example "FBX201600" for file version 7.5 which guarantees compatibility with Autodesk 2016/2017/2018 products.

sg->SetGlobalStringSetting( "FBXFileExportVersion", "FBX201600" );

sg.SetGlobalStringSetting( "FBXFileExportVersion", "FBX201600" );

sg.SetGlobalStringSetting( "FBXFileExportVersion", "FBX201600" );

Limitations

Currently there are a number of limitations to features supported in the various file formats

FBX

• Bone data and skinned meshes are not supported
• Selection sets are not supported
• There is limited support for blend modes and custom materials/shaders
• Due to limitations in the FBX SDK, all importer & exporter calls will be limited to one concurrent thread
• The FBX format can only contain one scene per file. Cascaded scene output will be converted into top-level nodes in the FBX scenes, one per cascaded scene in a depth-first pattern.
• Transforms on the root FBX node will be emulated with an inserted node at the top of the Simplygon scene hierarchy

glTF

• Different sampler wrap modes in S/T directions are not supported, S direction is used for both directions
• Cascaded scenes are output as separate glTF scenes in a depth-first pattern, with the top level scene set as the default glTF scene.

Extensions

• KHR_texture_transform is supported
• Any other required extensions will result in an error
• All other optional extensions are ignored

OBJ

• Cascaded scenes are not supported
• Bone data and skinned meshes are not supported

USD

• Only the UsdPreviewSurface material model is supported
• Blend shapes not supported