News December 04, 2020

There is more than one way to Clash-Check a model.

Table of Contents

Lewis Guy, Captain Awesome and Implementation Service Manager

A Time before Detection.

Thirteen years ago, when I started using Revit, life was a very much a heavy mix of 3D models and 2D drawings. It was very rare to have all disciplines modelling in 3D on the same project. During this period “clash detection” was still pretty much an unknown buzz word. Simpler times.

Ten years ago, 3D models were becoming more commonplace. With it came a plethora of complaints asking why Structural Columns were located in the middle of Architects Doors or why Pipes were going through a Wall, especially considering that there was an opening in the wall merely 500mm to the right of the Pipes location. For me, this is when I first heard about this mythical software solution “Navisworks”. Apparently, “Navisworks” was going to solve these problems by bringing them to our attention a lot sooner and helping us review the progress continuously throughout the project.

Oh, were there problems.

At the time, this was revolutionary. You can see every instance where an object hits another object. Wow!!! The issue with this was that because we were still coming to terms with 3D models, we often had a lot of problems. A LOT OF PROBLEMS. But as time went by, we all got better at this, and quickly we had very useful information within Navisworks. We didn’t necessarily have a great way of sharing this with others at this point, but we made it work, and our models were getting more and more coordinated as we went.

For a lot of people, this is still the main process for carrying out clash detection and there is nothing wrong with that at all. Then you add Revizto into that process and it more than solves the issue of sharing the information from within Navisworks with the rest of the teams.

Then, in 2013, this new software came across my desk. We had been asked by a client to coordinate using this tool called Solibri. Solibri is a tool that can do an incredibly advanced version of clash detection (as well as a simple clash detection) but also check data in the models. The biggest difference between Solibri and Navisworks is that Solibri only reads in IFC files whereas Navisworks lets you bring in native models from most modelling tools as well as IFC. By this point, across Europe at least, IFC files were becoming a regular deliverable on projects so this wasn’t an issue for us. So we started using it.

Solibri for Clash Detection

When you first open Solibri and start looking around the Rulesets it is quite daunting. But once you start spending more time in the Ruleset Manager it all begins to make sense and becomes a very intuitive tool to use. In Solibri the Rulesets are typically predefined, and you then start customising them to be more specific to meet your needs. You can start to classify groups of objects similar to Navisworks Search Sets which allows you to make the existing Rules more specific. And, because IFC files largely have their data structured in the same way it didn’t matter which authoring tool was being used, the rules worked.

In Solibri, the basic clash detection rule is very similar to how Navisworks does clash detection. You specify what your first component is and what your second component is. As with Navisworks, this can be an entire model (Structural Model) vs an entire model (MEP Model), it can be an object category (Wall) vs an object category (Duct) or it can be an object that meets specific criteria (Wall + Fire Rating > 30) vs an object that meets specific criteria (Ducts + Width > 100). It may look different, but this is the same as Navisworks SearchSets being used for clash detection.

Solibri then goes off on its own with its much more advanced version of clash detection. This advanced clash detection, at first glance, can look complicated, but once you spend the time getting to know it it is actually really simple but extremely powerful.

We can specify rules that check the maximum or minimum distances between objects from a face of your choosing.

We can start the check that objects like Doors and Windows have enough free space in front of them so that they can open properly without coming into contact with another Door or Window or even worse a Pipe or a Duct.

We can even start to check buildability and health and safety issues. Like, making sure that every edge with a drop has a handrail or balustrade to prevent someone or something from falling.

For me, the thing that takes the most getting used to, especially if you are coming from a Navisworks background is how Solibri lists the results.

You can switch between a Category Hierarchy (Default) view and a List view. The Category Hierarchy view has a predefined priority order meaning that it doesn’t matter what is Component 1 and what is Component 2 in the clash detection rule it will group it the same way.

In my example, “object category (Wall) vs object category (Duct)”, the Wall is the object it groups the results by. We can then see all the clashes on the screen at once

All the clashes with one wall.

Or the individual clash.

Solibri has the same issue as Navisworks whereby it’s great inside the tool but how do you share the information with the wider team? Solibri works with slides and presentations. Slides are images of the issues and presentations are collections of slides. These can be shared out as XLS or PDF reports but also they can be shared through a BCF and this is where Revizto can help with this process.

Whilst it may not be as slick as Navisworks using the Sync Clashes tool it really isn’t that different. The only extra step required in the Solibri workflow is applying a section box around the components before you create the slide.

Once the slide is created you can set information in Solibri or you can wait until it is in Revizto and make those changes there.

We can then import this BCF file into Revizto and it will then show up in the Issue Tracker. The data set in Solibri has transferred through but you could also set everything in here as required.

From Revizto we can now switch back to our modelling software so that we can fix the issue.

There is more than one way to check a model.

Typically, when you think of Clash Detection, you think of Navisworks, and that is fine. Navisworks is fine. But there are other tools out there that can do it. And yes, Solibri is restricted to IFC files, and yes, at first glance it doesn’t have the same simplicity as Navisworks. But as the complexity of our buildings change and we get more advanced at modelling them, maybe our clash detection tool needs to change as well.

And who knows what is around the corner in the world of clash detection. Watch this space…

About the author
Lewis Guy

Lewis Guy is a 14-year Construction Industry veteran from the UK and was a Revit Modeller and BIM Lead/Manager for years. He played a major role in overseeing Rambolls UK’s switch from Microstation to Revit and led Ramboll UK’s BIM Team and was the UK Lead of Ramboll’s Global BIM Coordination Team, and has worked on multiple, iconic global projects like the Al Rayyan Stadium for FIFA 2022 World Cup. At Revizto, he Focuses on strategic placement of Revizto within various industry workflows for client-specific needs, as well as helps train and document processes for each client.

There is more than one way to Clash-Check a model. Thirteen years ago, when I started using Revit, life was a very much a heavy mix of 3D models and 2D drawings. It was very rare to have all disciplines modelling in 3D on the same project. During this period “clash detection” was still pretty much an unknown buzz word. Simpler times.Ten years ago, 3D models were becoming more commonplace. 2023-11-14
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