Here you will find an explanation and best practices for solving Unsupported Data related synchronization errors.
Category: Unsupported
"Unsupported" typically refers to a situation where the selected Synchronizer does not support the data or file format you're trying to work with.
Info message: Failed to convert [<element description>].
Issue:
The above warning occurs when the connector has converted an element but cannot add that element to the iModel.
Cause:
After preparing the element, the connector attempts to add it to the iModel. If the element shares a code that already exists, the connector automatically clears the code and retries, so a duplicate code alone does not cause this warning. This warning is reported only when the element still cannot be added after that retry — typically because the element's class, category, or model is not valid or available in the target iModel, or the element does not satisfy the iModel's data rules. This is reported as a Warning, so synchronization of other elements continues; any child elements of the affected element are also skipped.
Solution:
Info message: "Permeability property value 55.400 ng/(Pa·s·m²) of Permeability dimension is ignored due to disputable Revit units."
Issue:
The permeability property value for the element is missing in the iTwin Viewer.
Cause:
In Autodesk Revit, permeability values are not a direct parameter or explicitly calculated property. Instead, Revit uses the concept of materials and their properties to simulate the behavior of real-world materials in a building environment. Permeability, in the context of building materials, typically refers to how easily water or other fluids can pass through them. According to Autodesk Revit Architecture Forum, this value may not always be calculated correctly, and for this reason, it is ignored during synchronization to the iModel. Keep in mind that the availability of certain features and tools in Revit can change with different versions, so the calculation of this value in Revit may be improved and included in the iTwin synchronization functionality in the future.
Solution:
This message is for your information only. We always recommend calculating permeability based on specific building parameters.
Please refer to Bentley support if you're sure this is wrong. If you have comments about the software (features or improvements you'd like to see), please visit the new iTwin Services Ideas portal to let us know. You can also vote on ideas others have posted, so be sure to let us know if an idea you see there is important to you.
Warning message: "Shared cell exploded due to non-uniform scale. Please consider changing the shared cell named [Name] to have a uniform scale."
Issue / Cause:
Shared cells in MicroStation significantly optimize DGN files through single-time storage of cell definitions, enabling efficient element management and decreasing file size. For comprehensive information on shared cells in MicroStation, please consult Bentley Systems' documentation. When synchronizing designs into iModels, it is essential to understand that iModels employ geometryparts as the equivalent of shared cells, yet they do not accommodate non-uniform scale geometry parts. This constraint necessitates the conversion of such shared cells into individual geometry elements to preserve data integrity and mitigate impacts on performance and workflows.
Solution:
To enhance iModel performance, it is advisable to employ shared cells with a uniform scale.
Warning message: "Element contains external geometry data which is not supported currently"
Issue:
One or more elements in the Navisworks (NWD/NWC) file contain geometry stored as an external geometry reference rather than as embedded primitives (meshes, lines, points, cylinders, etc.). The connector cannot read this geometry type, so the affected element is synchronized to the iModel with its properties and position in the model hierarchy, but the external portion of its geometry is omitted. If the element consists solely of external geometry, it will appear in the iModel with no graphics.
Cause:
Navisworks can store geometry for some components as an "external geometry" record, typically produced by certain source-format exporters or by referencing geometry held outside the normal fragment data. The underlying file-reading toolkit used by the connector does not currently expose the contents of these records, so the synchronizer has no geometric data to convert. This is a limitation of the current implementation, not corruption in the source file. The message is a warning only; synchronization of the rest of the file continues normally.
Solution:
Warning message: Large BRep processed as surfaces.
Issue:
The source file contains a 3D solid (a boundary representation, or "BRep," object) that is too large or complex to be brought across as a full solid. In order to not loose this geometry, it was converted as a set of surfaces representing the outer shell instead of a watertight solid.
Cause:
Effect:
Solution:
Additional Information:
Warning message: Root model <model identifier> is not a 3D model. Therefore, no spatial models or elements will be converted. Drawings and sheets may be converted.
Issue:
Cause:
Effect:
Solution:
Additional Information:
Error message: 2D attachments to 3D are not supported. 3D:[model name]. 2D:[attachment name].
Issue:
2D attachments to 3D are not supported. 3D:[model name]. 2D:[attachment name].
Cause:
This error indicates that a 3D source model contains a reference attachment to a 2D model. The iModel synchronization process requires a consistent 3D coordinate space for all spatial models. Attaching a 2D model into a 3D space is an invalid configuration for creating a spatially accurate iModel. Because this configuration is not supported, the connector must skip processing the 2D reference attachment, and its content will not appear in the iModel.
Solution:
Modify the source DGN file to remove the invalid 2D attachment from the 3D model.
Error message: Failed to create references subject. Parent[<parent model>]. Attachment[<attachment description>].
Issue:
While discovering the spatial models and their reference attachments, the connector tried to create a "References" Subject element in the iModel to represent a reference attachment, and that Subject could not be created. The References Subject is the organizational node under which the referenced model is brought into the iModel; without it, the connector cannot bring that particular reference attachment into the iModel. The parent model and the attachment description are included so you can identify which attachment was affected.
Cause:
This message is typically produced for one of the following reasons:
Effect:
Solution:
Error message: "While reading the IFC model, it was not possible to find a supported version of the IFC schema. It is also possible that the IFC file provided was not complete or corrupted: <schema version>"
Issue:
The IFC schema version of the model provided is not currently supported.
Cause:
The IFC schema version of the model provided is not currently supported.
Solution:
Please refer to this link for more information on which versions of IFC are currently supported. In order to synchronize the data, it must be re-exported from the source application using one of the supported IFC versions indicated in the above link.
Error message: Unknown or unsupported raster file format: <file name>
Issues:
While converting a raster attachment referenced by a DgnV8 file, the connector inspected the raster file and could not determine a known image format for it. Because the format is unknown or unsupported, the raster cannot be read and converted, so that attachment is skipped. The conversion of the rest of the file continues; this is reported as an error for the affected raster only, not a fatal error that stops the whole job.
Cause:
This error typically occurs for one of the following reasons:
Effect:
Solution:
Additional Information:
Warning message: "While reading the IFC model, it was not possible to find a supported version of the IFC schema. It is also possible that the IFC file provided was not complete or corrupted: <schema version>"
Issues:
The following warning occurs when the connector encounters a Detail view (detail callout) that it does not convert. Message can appear as either:
Cause:
The connector's dynamic view converter only supports projected views — sections, plans, and elevations. Detail views (detail callouts) are not supported, so they are intentionally skipped during synchronization. This is a known limitation, not a data error; the warning is informational. The underlying content referenced by the detail (its model/drawing geometry) is still converted through its own model.
Solution:
No action required in most cases: Detail views are expected to be skipped. The graphics they reference remain available through the drawing/model they belong to.
If the detail view representation is needed in the iModel: this is a current product limitation of the dynamic view converter — capture the requirement with Bentley Support so it can be tracked; there is no source‑side setting that forces Detail callouts to convert.
To reduce the warnings: if the Detail callouts are no longer needed in the source design, removing or replacing them in the DGN will stop them from being reported.
Locating the items: each skipped Detail is listed with its view name, element id, and source file (in the consolidated entry, the full list is provided in the attached CSV) so you can identify them in the source file.