iModel Display Extents

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.

Size recommendations

While there typically are no hard limits imposed on the size of the Extents, we would recommend not exceeding these maximums:

  • For the height of the Extents, the recommended maximum is 2 km.
  • For the length and width of the Extents, the recommended maximum when a GCS is defined is 350 km and 20 km for iModels that are not map projections (only ECEF transform defined). 

Please refer to the individual product documentation to determine if any limitations are imposed.

Set the Extents

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.

Visualize the Extents

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

 

Potential data issues

There are cases where the result is not as expected after synchronizing BIM files to an iModel. Examples:

  • Source models had very distant elements

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:

  1. Elements were excluded from the Extents
  2. Extents volume issues

Depending on your needs and practices, you should update the source files to place such elements correctly or delete them. 

  • Partially visible data on iModel

There could be different reasons if you notice missing models when visualizing the data. 

  • If the whole model is not visible, it is possible that the source file was in a distant location or had a wrong geographical coordinate system. You may need to apply a transform to place it correctly or change the origin or coordinates in the file so that it comes into the correct location when synchronized.

  • If some data from iModel looks like 'cut,' it is possible that the wrong spatial root file was specified, resulting in false original Extents values. You may need to adjust the Extents to match the boundary of the project as needed.

Image 5 - Partially visible iModel

Image 6 - Models or all iModel is outside of Extents

  • iModel is in the wrong location

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

Change the Extents

Bulb 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.

Synchronization Report

The file without geo-coordinates projection

Revit_0021. Severity: Info

Diamonds 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

Diamonds 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)

Elements were excluded from the Extents

Dgn_0205. Severity: Error

Diamonds 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

Diamonds Error message: 562 Outlying elements were ignored when calculating project extents.

Dgn_0203. Severity: Info

Diamonds Error message: In ModelName: <model name> elements out of range < [Element_Name,Element_Id]>

Dgn_0204. Severity: Info

Diamonds Error message: In ModelName: <model name> and FileName: <file name> elements out of range < [Element_Name,Element_Id]>

Issue: 

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:

  • Missing elements 
  • Fuzziness in the map display 
  • Inferior performance 
  • Non-functional fit/rotate function 
  • Invalid or displaced geolocation 
  • Misaligned elements within the Model 
  • Oversized extents in viewing. These may be detected by the Diagnostic tool; refer to the Visualize Extents.

Causes: 

  • Incorrect Data Location: The global origin of the file could be distant from the modeled data location. 
  • Geo Coordinate Issues: Absence or misuse of geo coordinate information in the iModel. 
  • Wrong Seed File: Using the wrong file to initialize the iModel can lead to problems. 
  • Incompatible Geographic coordinate system (GCS) Definitions: Care must be taken with GCS definitions during synchronization. 
  • Reality Data Concerns: Import reality data with compatible GCS definitions. 
  • Invisible Stray Elements in Applications like MicroStation: These may cause synchronization problems in an iModel. 
  • Input Design Data without GCS: The location cannot be deduced from it. 

Solution:

  • Review GCS Systems: Ensure there are identical GCS systems in the source files. Fix any inconsistencies. Each design application will have specific information about setting and using GCS data. You can find more information in the iTwin Spatial Alignment articles or directly in design applications documentation. In the case of dgn files, file referencing support could be used as a technique to locate incompatible files. 
  • Check Design Elements: Ensure elements are near the main design file and not more than 2 km above sea level. Refer to size recommendations. You can identify any outlier elements by viewing the synchronization report.
  • Define Maximum Extents if needed: If you can't fix the input data, use this guide on creating an iModel that will help constrain the iModel extents. 
  • Synchronize Files in the Correct Order: 
    • For Reality Data: Synchronize with a defined GCS first, a DGN with an identical GCS second, followed by other models. 
    • For non-DGN files: Synchronize a DGN with a defined GCS first, followed by non-DGN models next. 
    • For files without a GCS defined: Synchronize a DGN with a defined GCS first, followed by models with an undefined GCS next. 

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.

iModel Display Extents have been adjusted

DgnV8_0191, Dgn_0215. Severity: Error

Diamonds Error message: Project Extents have been adjusted to exclude outlying elements - Element Id: <element ID>, Model Name: <model name>, File Name: <file name>.

iModel Display Extents volume issues

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

Potential errors:

  • Diamonds Error message: Project extents are too tall: <value> meters (expected less than 900 meters). Element geometry this expansive will affect display performance and often indicates corrupt elements or transforms.
  • Diamonds Error message: Project extents are too low: <value> meters (expected greater than 11000 meters). Element geometry this expansive will affect display performance and often indicates corrupt elements or transforms.
  • Diamonds Error message: Project extents are too high: <values> meters (expected plane dimension less than 9000000). Element geometry this expansive will affect display performance, and often indicates corrupt elements or transforms.
  • Diamonds Error message: Project extents are too high: <values> meters (expected less than 8850 meters). Element geometry this expansive will affect display performance, and often indicates corrupt elements or transforms.
  • Diamonds Error message: Project extents are too narrow: <alues> (ratio of largest footprint dimension to height; expected greater than 0.10). Element geometry this expansive will affect display performance, and often indicates corrupt elements or transforms.
  • Diamonds Error message: Calculated extents along z is too big 48554.598741 x -68.050667 = 48622.649408 m. Clamping it to 33085.601622 x 15389.523222  SPx_0002. Severity: Warning. 
  • Diamonds Error message:  Element '' is excluded due to invalid extents: too small height 0.00 mm. Please try to re-publish this Review file from original source again.

Solution:

  • Check Design Elements: Update the source files to correctly place or delete elements depending on your needs and practices.
  • Review GCS Systems: Ensure identical GCS systems are defined in the source files. Fix any inconsistencies. Each design application will have specific information about setting and using GCS data. You can find more information in the iTwin Spatial Alignment articles or directly in design applications documentation. In the case of dgn files, file referencing support could be used as a technique to locate incompatible files. 

Geo-location point moved to the local zero-coordinate

Revit_0016. Severity: Warning

Diamonds 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

The site is located too far from the coordinate system origin

Ifc_0010. Severity: Warning

Diamonds 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

Diamonds 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]"

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