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AECbytes Product Review (March 31, 2009)

Solibri Model Checker

Product Summary

Solibri Model Checker is used to analyze BIM models saved in the IFC format for potential problems, conflicts, or design code violations. It also includes visualization, walkthrough, interference detection, model comparison, collaboration, and quantity take-off capabilities.

Pros: Only application of its kind; powerful compression technology that reduces model sizes dramatically; ability to combine multiple disciplinary models in one file; well-organized interface that is relatively easy to learn and use; excellent 3D visualization interface; extensive range of rule sets available to use with the application; ability to configure rules to desired standards and to create new rule sets; ability to easily generate presentations and reports showing the checking results; can be used to ensure the integrity of a BIM model for use in other design and analysis tools; provides the foundation for developing automated code-checking and other advanced applications.

Cons: Model import options limited to IFC format only; documentation not sufficiently detailed to speed up the learning experience.

Price: Single workstation license is $6,000; network license is $7,000; pricing includes first year subscription and ½ day of training.

I was first introduced to Solibri Model Checker at an "Interoperability" workshop I attended in San Francisco all the way back in Feb 2001. The event was co-hosted by the Lawrence Berkeley National Laboratory and Pacific Gas and Electric, and it was used to showcase how the open-standards IFC file format could be used to link various analysis tools to the building data in a CAD model (the term “BIM” hadn’t been introduced yet) to check different aspects of the design. Solibri Model Checker was one of the analysis tools that was demonstrated, showing how it could be used to check the building model for modeling errors, such as overlapping walls, as well as for design errors, such as insufficient areas or non-compliance of egress requirements.

A relatively new tool at that time, Solibri Model Checker still remains one of the only applications available for model checking, although its repertoire has now grown to also include model visualization, clash detection, comparison of model versions, and quantity take-off. A number of related products have been developed as well. Solibri Model Checker also remains, to date, one of the few applications that was developed specifically to work with the IFC file format, and is thus an important “poster child” for the interoperability movement. Let’s take a detailed look at how the application works and see what it can do to improve the BIM-based building design process.

Overview of Solibri Model Checker and Related Products

The key value proposition of Solibri Model Checker is finding out potential problems, conflicts, or design code violations in a building model. This is a task much more complex than it sounds—for a start, the model itself has to incorporate a certain level of intelligence and building semantics, so that the model checker can interpret it, analyze it, and then point out any errors in it. This is the one of the key concepts behind BIM (building information modeling) as well, so even though Solibri Model Checker was developed before BIM was officially introduced in the AEC industry, the success of BIM has made Solibri Model Checker a much more compelling and viable product.

As mentioned earlier, the application checks for both modeling errors as well as design errors. Checking for modeling errors is important to ensure the integrity and quality of the model for producing reliable results in other applications in which the model will be used, such as energy analysis, structural analysis, cost estimating, 4D scheduling, multi-disciplinary coordination, and so on. This can be seen as a QA (quality assurance) check for a BIM model. Once all the modeling errors are resolved (this has to be done in the original model authoring application) and the model passes the QA check, it can then be subjected to the more advanced checks for design errors, which can include code requirements, ADA accessibility guidelines, egress requirements, and so on (see Figure 1).


Figure 1. Checking the escape routes for a floor using Solibri Model Checker.

The checking is done on the basis of rules grouped into related “rule sets,” which form a related yet independent component of the application. This allows different rule sets to be developed and used for projects of different types and in different locations. The application ships with a number of default rule sets; others are continuously being developed, and can be accessed from the Solibri website. The rules can be customized by users to some degree, and the company also undertakes the development of fully customized rule sets, if required, on a consulting basis.

In addition to the core model-checking capabilities, Solibri Model Checker also includes various other functionalities: the ability to bring multiple models together and save them in a single, highly-compressed SMC file; the capability for rule-based clash detection as opposed to just the geometry-based clash detection offered by an application like NavisWorks; model visualization and walk-through capability; the ability to compare two versions of a model and see the changes; the ability to generate quantity takeoffs that can subsequently be fed to estimating applications; and reporting and presentation capabilities to capture and share the model-checking results with others.

In addition to the main Solibri Model Checker application, Solibri has also developed some related products that are available for free to users. This includes the Solibri Model Viewer, which includes the model viewing, navigation, presentation, and reporting capabilities of Solibri Model Checker, but is missing the checking capabilities. It acts as a free viewer for IFC and SMC files, and also allows the analysis results obtained with Solibri Model Checker to be shared with the extended design team, the client, and other interested parties. Another related application is the Solibri IFC Optimizer, which can be used to optimize IFC files exported from BIM applications, reducing their size to 5-10% of the original. It works by removing all redundancy and duplicate elements. The smaller files are easier to send by email; they also load faster and use less memory in IFC applications. And finally, there is the Solibri Issue Locator, which allows the issues discovered in Solibri Model Checker to be viewed in the original BIM authoring application, allowing them to be fixed more easily and quickly (see Figure 2). The Solibri Issue Locator is currently available only for ArchiCAD, but versions for other BIM applications such as Revit and Bentley are hopefully being developed by Solibri as well.


Figure 2. Opening the Solibri Issue Locator within ArchiCAD to see the list of problems that were detected with the model.

Let’s move to look at Solibri Model Checker in more detail.

Opening and Exploring Models

The starting point for Solibri Model Checker is a building model created in an IFC-compliant application, and saved in the IFC format. This model can then be opened in the application, and subsequently saved in the native SMC format, which is much smaller than both the native file size as well as its IFC version. For example, the Revit model shown in Figure 3-a was close to 19 MB, the IFC file generated from it was 42 MB, and the SMC file generated by opening this IFC file, shown in Figure 3-c, was 1.72 MB. This makes Solibri’s compression capability even superior to that of NavisWorks (see my review of NavisWorks 2009, in which I used the same Revit model and found the corresponding NavisWorks NWC file to be 2.5 MB). You can also bring in multiple IFC models and save the combined model in one SMC file, to achieve the same compression benefits in addition to being able to coordinate the models.

When an IFC file is first opened, the application asks you to confirm the discipline the model belongs to. This is important for the rules to work correctly when checking the model later. Figure 3-b shows how the Revit IFC file has been automatically identified as belonging to the Architectural discipline, so all that is needed is to confirm the selection. The model is then opened in the user interface, ready to be explored and checked. There are three main components to the application, as indicated by the three tabs shown at the top of the interface: Model, Checking, and Presentation. These are respectively for navigating the model, checking it, and compiling the results into presentations if required. In the Model layout, shown in Figure 3-c, you can see the graphics window, model tree, and information about the selected component. As you can see from the Info panel showing the properties of the selected beam, the object attributes from the Revit model are maintained in the IFC file imported into Solibri Model Checker.


Figure 3. (a) The Revit model that is exported as an IFC file for use in Solibri Model Checker. (b) Verifying the default disciplinary selection of the imported model. (c) Exploring the imported model in Solibri Model Checker.

The navigation capabilities of Solibri Model Checker include the usual Zoom, Pan, Spin, and Walk tools. There is also a Game mode that allows you to walk inside the building using typical gaming controls. The Model Tree can be viewed in three different ways: by containment, which was the view shown in Figure 3-c; by object types; or by layers. Double-clicking on any element or category of elements automatically zooms the view to the selection. Using this capability in conjunction with the ability to show unselected objects in a transparent mode, as shown in the top image of Figure 4, provides a useful way to explore different parts of the model in context with other elements. You could also select some elements from the model tree and turn off the visibility of the other elements, as shown in the lower image of Figure 4.


Figure 4. Different ways of exploring the model. In the top image, some objects are selected and the rest are set to transparent, while in the lower image, a whole floor of the model is selected and the unselected elements are turned off.

Other navigation capabilities include the ability to set the model quickly to several predefined viewing angles such as Top, Right, etc., and a Sectioning tool that can be used to slice the model with up to six clips. This is particularly helpful when exploring the interior of a detailed model made up of several different disciplinary models, such as the one shown in Figure 5. A Dimension tool is also available to measure the distance between two objects or surfaces.


Figure 5. Using the Sectioning tool to view the interior details of a model.

Checking Models and Working with Rule Sets

The checking functionality of the application can be accessed by going to the Checking layout. Here, you would start by loading the specific rule sets that you want to use for checking the model. Solibri Model Checker ships with a large number of rule sets, categorized by discipline to make their use more intuitive. The available Architectural and Structural rule sets are shown in Figure 6. In addition, there are also some MEP rule sets and a few generic rule sets. You can select multiple rule sets against which to check the model. However, a sequential approach to model checking is recommended, where you run some of the basic checks, resolve those issues, and then proceed to the more advanced checks.


Figure 6. The Architectural and Structural disciplinary rule sets that are included with Solibri Model Checker.

After loading the desired rule sets, the checking can be initiated by clicking on the Check Model tool. While the checking is in progress, you can expand the rule tree and start analyzing the results that are completed. The status of each rule is displayed in the table alongside it, showing whether it has passed or if problems were detected, with different icons used to designate the criticality of the problem (ranging from low to high). The results can also be filtered based on status. More details on a rule and all the elements that have not complied with it can be seen in the Info and Results panels respectively, as shown in Figure 7. Selecting specific elements in the Results windows displays only those in the graphics window, along with the footprint of the related building floor to put them in context.


Figure 7. Checking the model against one of the architectural rule sets and viewing the details of one of the instances where the Space Validation rule is not met. This particular issue is caused by the space intersecting with five columns.

Additional options are available by right-clicking on any of the issues in the Results window. This opens up the Result Details dialog shown in Figure 8, where you can make a decision about the issue, and add any related comments. Additionally, you can save this view as a viewpoint for convenient access later, and also save it as a slide in the Presentation module. All the results captured for a rule set in this manner can be automatically converted into a slide show for viewing in the Presentation module, as shown in Figure 9. From here, the whole presentation can be exported as a report in varied formats to share with other team members, and the necessary fixes can be made in the original authoring application of the model. A convenient IFC update option is available, allowing you to update the model with a new version of an IFC file. Decisions, snapshots, and comments stay unchanged for those parts that have not been affected by the update.


Figure 8. Commenting on the result in the Result Details dialog and saving it for viewing in the Presentation module.


Figure 9. Viewing the slide of the saved result in the Presentation module.

Types of Checks   

Now that we have an overall understanding of how Solibri Model Checker works, let’s take a brief look at some of the types of checks that can be done. The “BIM Validation” rule set shown in the previous section can be used for general quality assurance of the model, verifying that all the building components are present and that there are no major issues. This rule set is available for both conceptual and advanced stage models. Once the model passes these validation checks, it can be checked for more specific criteria, such as egress analysis (shown earlier in Figure 1) and accessibility analysis, as defined by ADA and ABA guidelines (shown in Figure 10-a).

Solibri Model Checker also includes a number of rule sets for what it calls “spatial coordination,” which goes beyond geometry-based clash detection alone. This includes the “Space Validation” rule set, which checks that the architectural design has spaces defined according to surrounding walls (see Figure 10-b); the "Structural versus Architectural Models" rule set, which checks the architectural and structural models brought in together to verify that load bearing walls, columns, beams, slabs, etc., are equally located in the two disciplines, helping to avoid misleading issues such as pipes clashing with columns in the structural design but not in the architectural design; and the "Intersections Between Domains" rule set, which checks the structural design and MEP design and finds the clashes on structural elements (see Figure 10-c).


Figure 10. Examples of various other checks enabled by different rule sets. (a) Accessibility. (b) Space Validation. (c) Interference.

Even functions such as model comparison, quantity take-off, etc., are enabled by rule sets. The "Model Revisions Comparison - Architecture" rule set, shown in Figure 11-a, allows you to import the previous version of the design and then the later version and run comparison rules. The results are color-coded, showing what has been added, removed, or modified in the model. A summary report on quantities changed by construction type is also generated. A sample of the results of the “Quantity Takeoff” rule set is shown in Figure 11-b, which can be exported to estimating applications. Another example of a rule set enabling specific functionality is the “Visualization” rule set, shown in Figure 11-c. It color codes different component types, making it easier to spot any inconsistencies.


Figure 11. Examples of other functionality enabled by rule sets. (a) Model comparison. (b) Quantity take-off. (c) Visualization of walls color-coded by type.

Needless to say, all these rules and rule sets are the key to the application and they can be viewed in more detail as well as edited, if required, in a separate component of the application called the Rule Set Manager (see Figure 12). Here you can browse through all the rule sets, and change the parameters of specific rules to configure them to fit project specific needs. For example, you can specify what should be the minimum thickness, length, and height of walls; the ratio of the window area to the floor area of spaces; the maximum allowable distance of any space to the nearest exit when checking for valid escape routes; the allowable overlaps when checking for intersections between any two types of components; and so on. You can also create whole new rule sets from the rules existing in the Rules library, configuring their parameters as required.


Figure 12. The Rule Set Manager Interface for browsing and editing rules.

Analysis and Conclusions

Solibri Model Checker is a unique application that has no real competitor in the AEC technology space yet. The only application with some of its functionality is NavisWorks, but that is focused primarily on coordination and clash detection. For an application that charts such completely new territory, Solibri Model Checker is surprisingly well put together, and is relatively easy to use. The 3D visualization interface is excellent, and the three different components of the application are nicely organized. The visualization of the checking results is particularly well implemented; for example, the sectioning capability can work in conjunction with the results of the spatial coordination, allowing issues to be seen as the model is being sectioned. Solibri Model Checker is well suited to being used by design firms as their internal QA tool to improve the quality and consistency of their models, and can also be used by contractors to validate that the models they are receiving from the design team meet their specific criteria as captured in their own customized rule sets.

As far as limitations goes, the application could do with some better documentation to enable faster learning, particularly on how to edit and create rule sets, which are the key to the application. Also, its near-complete reliance on the IFC file format ties its fortunes too closely with that of the IFC, and it would do well to find ways of working directly with the file formats of all the major BIM applications, as NavisWorks has been able to do. Building interfaces such as the Solibri Issue Locator with Revit and Bentley, in addition to the one currently available for ArchiCAD, is also essential to make the design iteration loop between modeling and checking faster and more efficient.

Solibri Model Checker may not yet be a mainstream product, but that is likely to change as we put our BIM models to more intelligent uses rather than primarily for generating construction documentation, visualization, and clash detection. In my reviews of BIM applications, I have pointed out that most of them do a poor job of guaranteeing model integrity, so an application like Solibri Model Checker will become increasingly critical as we develop more applications to work with BIM models, to ensure that the model has been created correctly for their use. In time, I hope that BIM applications will evolve to a point where they can include their own internal checks for model integrity, allowing an application like Solibri Model Checker to focus most of its development efforts on the more challenging and critical task of checking for design errors.

The automated code-checking initiative in the US is already well underway, and it is powered by a customized version of Solibri Model Checker (see the section entitled “Development and Implementation of Automated Code Checking in the US” in the article on the AIA TAP 2007 Conference). In addition to enabling checking for local code compliance, Solibri Model Checker can also eventually be expanded to include large databases of rule sets for different building types such as hospitals, hotels, offices, etc., allowing designs to be checked against type-specific standards and best practices. The ability to quickly and automatically check a building design for the satisfaction of codes and established design standards is a critical step towards a more intelligent and sophisticated design process, which will allow buildings to be subjected to much higher levels of quality control than those in place today.

About the Author

Lachmi Khemlani is founder and editor of AECbytes. She has a Ph.D. in Architecture from UC Berkeley, specializing in intelligent building modeling, and consults and writes on AEC technology. She can be reached at lachmi@aecbytes.com.

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