iModel Display Extents represents a bounding box or the volume of interest of the iModel's coordinate system, and all geometry of an iModel must be contained within such limits. Individual iModels can have separate extents within an iTwin.
Image 1 - iModel with shown Extents
In this manner, multiple iModels can be oriented relative to one another and relative to external reality models, cartographic and geographic information systems, etc.
While there typically are no hard limits imposed on the size of the Extents, we would recommend not exceeding these maximums:
Please refer to the individual product documentation to determine if any limitations are imposed.
When you create an iModel in various Bentley products, you might have seen functionality to define Maximum Extents as 2D rectangle. We always recommend setting those up, as this will optimize viewing performance, making elements outside the interest area not shown. Refer to the Potential data issues chapter to learn more.
Image 1 - Maximum Extents example in ProjectWise 365
If you synchronize files using iTwin Connectors, the actual Extents will be statistically determined based on your data (as long as it is within the defined Maximum Extent area), and it could be smaller than the area you set up as Maximum Extents. In subsequential synchronizations, when a lot of new data is found, the original Extents might be adjusted to cover the probable new interest area.
Image 2 - Extents determined by iTwin Connectors
If iTwin Extents were set or adjusted manually, the iTwin Connectors will always honor those values and will not modify them further independently of your actual data.
Please refer to the individual product documentation to determine if and where such Extents functionality is exposed in the interface. For example, in some viewers, that might be under Diagnostic Tools, as shown in an image.
Image 3 - Extents exposed in Design Review
For developer resources, you can find more documentation on the iTwin.js iModels overview page or try the "Visualize Project Extents" sandbox.
Image 4 - Visualize Project Extents sandbox
There are cases where the result is not as expected after synchronizing BIM files to an iModel. Examples:
Your design file may have contained a few elements far from the model's origin. In such a case, you would not see them in iTwin-based viewers by default, as they would be outside of Extents. iTwin Connectors would identify statistically outlying elements. Such issues would be exposed in the Synchronization Report interface as errors:
Depending on your needs and practices, you should update the source files to place such elements correctly or delete them.
There could be different reasons if you notice missing models when visualizing the data.
Image 5 - Partially visible iModel
Image 6 - Models or all iModel is outside of Extents
If iModel is in the wrong location, adjusting Extents will not move the iModel itself. You need to update the source files to place data correctly. You can find best practice guides on bringing spatially aligned data to an iTwin here.
We are researching the requirements for iTwin Realignment Tooling, which could help adjust iTwin Extents and move iModel or individual models into correct locations if that can not be done by editing the source files with design applications. If you are interested in participating in such research or providing feedback in usability lab sessions, please fill out this form: https://forms.office.com/r/FBY5FYSy1n, and we will contact you with more details.
Revit_0021. Severity: Info
Error message: The file was published without geo-coordinates reprojection. Its Survey Point got -38.11425 145.13616 coordinates instead of 42.41486 -71.25807 with reprojection usage.
Revit_0023. Severity: Info
Error message: This file was reprojected to (170964.2, -284817.8, 0.0) from the original location (0.0, 0.0, 0.0) in WGS84 42.99100 -71.46100 geo-coordinates at (0.0, 0.0)
Dgn_0205. Severity: Error
Error message: Element(s) were considered statistical outliers and were excluded from the project extents. They may not be visible in this project. This often indicates corrupt elements or transforms.
Dgn_0200. Severity: Info
Error message: 562 Outlying elements were ignored when calculating project extents.
Dgn_0203. Severity: Info
Error message: In ModelName: <model name> elements out of range < [Element_Name,Element_Id]>
Dgn_0204. Severity: Info
Error message: In ModelName: <model name> and FileName: <file name> elements out of range < [Element_Name,Element_Id]>
For optimal viewing performance, the iModel display system uses a range of elements to be included in the display. If the data synchronized with an iModel connector is not well-formed, you may see some of the following issues:
iTwin Spatial Alignment articles will help you validate data positioning and make required changes to design applications based on your data type.
Refer to the error "Elements were excluded from the Extents" description.
DgnV8_0191, Dgn_0215. Severity: Error
Error message: Project Extents have been adjusted to exclude outlying elements - Element Id: <element ID>, Model Name: <model name>, File Name: <file name>.
If any of the issues listed below are shown in the Synchronization Report, there are issues with your current data. As a result, the Extents volume could not be appropriately supported and will affect display performance.
Image 7 - Extents volume issues
Revit_0016. Severity: Warning
Error message: Geo-location point (Survey Point 0.000, 0.000) was moved to local zero coordinate (Project Base Point 320000.002, 5813100.035) due to too large distance 5822 km between them to provide more accurate elements placement. But it's better to follow suggestions from Autodesk to fix this right in the source file: http://help.autodesk.com/view/RVT/2018/ENU/?guid=GUID-3F79BF5A-F051-49F3-951E-D3E86F51BECC
Ifc_0010. Severity: Warning
Error message: Site located (336.607,5779.87,0.002666) km from coordinate system origin. It is too far and globe placement may be inaccurate. Consider re-creating the input file with better positioning.
DgnV8_0000. Severity: Error
Error message: "Failed to convert [Error: Geometry in the published model is too far away from the origin, please keep your elements centered around the design file origin]"