Comparing Models in 3D

Feature Overview

The model comparison feature enables comparing .IFC and .Tekla models visually in 3D. It detects changes in objects that are uniquely identified by a GUID. Changes are detected in the object geometry and part level properties. The comparison feature is based on the “diff model” concept. A diff model is a special model created by Trimble Connect and it contains only the differences between the models or model versions that are being compared. In other words, the comparison result is always a diff model. The user can choose to view the comparison result temporarily or save the comparison result in a Connect project folder.

Selecting Models for Comparison

You can select for comparison any two versions of a single model or any two models in the project.

Launching Model Comparison

Select 1 or 2 models in the models panel and click the compare icon:

In the “Choose versions to compare” dialog, you can change the models and/or model versions before clicking the Compare button. If the “Hide other models” option is selected, all other models will be hidden and the ghost mode will be turned on: This enables you to view the comparison result in context of the original model, but in a way that the original model is not selectable so you can focus on viewing the changes only.


Alternatively, you can select 3 or more models and launch a batch comparison by clicking on the compare icon. The batch comparison automatically compares the latest versions of the selected models with their previous versions and saves the comparison results in the Connect project under a folder called “Model Comparisons”.


Viewing Comparison Result in 3D

After clicking the Compare button, the comparison panel opens and the comparison result is displayed in 3D. The different types of changes are shown with different colors:

  • Inserted objects = Green

  • Changed/Modified objects = Grey (with red outlining highlighting how the object geometry has changed between the compared models)

  • Deleted objects = Red

  • Objects with only property/attribute value changes = Blue


In the comparison panel you can

  • See the model names and versions that are being compared

  • Show and hide the ghost objects by selecting/deselecting the Ghosts checkbox

  • Close the comparison result


Close comparison button has 2 options associated with it:

  • Unhide other models: If the option is selected, the models that were hidden when launching the comparison (using the “Hide other models” selection) will be shown again

  • Save comparison: see section “Saving comparison result” below.


While a comparison is active, there is a yellow message box floating in the top of the 3D view (“Model comparison is ongoing”). You can zoom into the comparison result and return to the comparison panel by clicking the “Go to Comparison” button in it.

Different types of changes are placed into separate layers in the comparison result. To explore the different types of changes in their respective layers, open the Objects panel and Group by Layer. Alternatively, open the comparison result in the browser 3D viewer, open the Layers panel and toggle the visibility of the layers. Note that the comparison result must be saved in the project folder before viewing in the browser. The available layers and the object colors in the layers are listed below:

  • Inserted: Green

  • Removed: Red

  • Changed - New: Grey (the new geometry)

  • Changed - Old: Red outline (the old geometry)

  • Changed - Properties: Blue (contains objects where only property value was changed without a geometry change)


Saving Comparison Result

When saving the comparison result, a new folder gets automatically created in the Connect project. The name of the folder is “Model Comparisons”. The comparison results (e.g. diff models) are saved in the folder using an automatic naming convention. For example, when comparing “panorama.ifc” version 2 to version 1, the comparison result name is “panorama.ifc_2-1”. The “Model Comparisons” folder and the saved comparison results are normal folders/models. They are synchronized with the online Trimble Connect project and are available to other project members for collaboration.

Comparing Properties

The changed part level properties are included in the comparison result. You can view the changed properties in the Connect for Windows properties panel or in the Connect for Browser 3D viewer data table. The comparison result must be saved in the project folder before viewing in the browser.

Asterisk in the end of the property name denotes a change in a property value.

To view the properties of a comparison result in Connect for Windows, double click an object in the 3D view to open the properties panel.

To compare properties in the Connect for Browser 3D viewer data table, open the data table and configure the columns to show the changed property values (the properties with the asterisk in the end of the property name):

What is detected as a change?

Keeping in mind the foundational characteristics that a) model format must be .IFC or .Tekla, b) objects must have a GUID and geometry and c) only part level properties are checked by the comparison, then a change is detected if the change is above the tolerance values listed below:

  • When an object with a GUID has a geometry change more 0.01 mm

  • When a numerical length property value changes more than 0.6 mm

  • When a numerical mass property value changes more than 0.1 % and more than 1 g

  • When a numerical area property value changes more than 0.1 % and more than 1 mm2

  • When a numerical volume property value changes more than 0.1 % and more than 1 mm3