Rhino Worksession Guide: Working with Reference Files on Large Projects

In Rhino 8, Worksession lets you split a large project into separate model files and use them as references in a single working session. According to McNeel’s official documentation, the feature allows one team member to work on the active model while viewing other files as references. When a file is open for editing, other team members can view it, but they cannot edit the same file at the same time. This guide explains how to add files through Worksession Manager, save a session, manage reference layers, and limit model scope for better performance.

Which workflows suit Worksession?

Worksession helps you view models together without merging them into one file, which is useful for large projects whose different parts are stored in separate files. Linked geometry is used as reference; it cannot be moved or scaled directly. However, it can serve as input for creation commands such as Copy or ExtrudeCrv. This lets you create new objects based on geometry in a source model without editing the source model itself.

A range of file formats that Rhino can import can be added to a Worksession. However, only .3dm files can be made active; other formats remain linked as references. For this reason, the team should decide in advance which file will be worked on and which files will be used only as sources.

Worksession should not be confused with blocks or the Import command. Blocks are reusable components within a model that behave like a single object; placed instances can update when the block definition changes. Import merges objects from another file into the current model. Worksession, by contrast, keeps different files as references outside the active model. If objects from an external file need to be added as blocks, groups, or individual objects, use the Insert options.

Setting up a Worksession and managing files

1. Open the model you want to edit. Decide which .3dm file will contain the active work. Other supported files can be added to the session as references.

2. Open Worksession Manager. Go to File › Worksession. In Manager, select the files using Attach. Alternatively, drag a supported geometry file from Windows Explorer into the Rhino window, then choose Attach file in the dialog that appears.

3. Check the role of each file. The active model is open for editing; other added files are used as references. Lock Info in Manager shows the linked file’s lock status and information about who has it open. In team workflows, checking a file’s status helps prevent someone from accidentally trying to work on the same model.

4. Save the session. In Worksession Manager, use Save or Save As to save the session as an .rws file. Each user manages their own .rws file; these files are not intended for shared use. The Rhino model files used as references are the ones that need to be shared.

5. Refresh references. To bring changes made to a source file into the session, select the linked file in Manager and use the Update command. When a Worksession file is opened, the models in the session are loaded; the active file is editable, while the others remain references. Opening a new Worksession may close the current model, so pay attention to the save prompt for any changes.

Layers, memory, and content conflicts

The geometry in a linked file appears with its own layers beneath a parent layer named after the file. You can change the color, visibility, and lock status of reference layers, but you cannot add layers to the linked file or delete its layers. Using layers within these limits makes it easier to distinguish between different reference files.

For large reference models, LimitReferenceModel can be used to keep only the area you are working on in memory. The command prompts you to draw a sphere defining the area of interest. Reference objects that are outside the sphere and do not touch its surface are unloaded from memory; this can make the view more responsive or reduce unnecessary visual clutter. For models with previously applied limits, RemoveLimits reloads the Worksession file to restore the unloaded objects.

PurgeRefObjects removes selected Worksession reference objects, but this action cannot be undone with Undo. To reload the objects, either make another linked file active or use Refresh All in Worksession Manager. For this reason, it is important to know how you will restore objects before using purge commands.

When adding or activating files, you may encounter materials, environments, and textures with the same names but different settings. The ImportRenameConflictingEx (import and attach) and PasteConflictOption (paste) values in Rhino’s advanced settings determine how these conflicts are handled.

The values in the table describe the behaviors defined in the documentation; they do not represent a single right choice for every project. In particular, value 2 can replace existing content, so it should be selected according to the team’s standards.

Practical notes for architecture, interior design, and archviz

In architectural projects, you can keep the main model, different project sections, or surrounding geometry in separate files and view them as references through Worksession. The team should clarify which .3dm file is active, where references are stored, and whether everyone can access those sources. Worksession does not make reference geometry editable; any required changes must be made in the source file, after which the linked model should be updated.

When preparing archviz work, it can be useful to create new objects based on reference geometry. However, if you need to move objects directly from the source file into the current model, consider Import or Insert instead of Worksession: Import merges objects into the current model, while Insert offers options for adding an external file as blocks, groups, or individual objects. This lets you choose a file structure based on the type of editing required.

Common mistakes:

• Treating the .rws file as a shared project file: Each user keeps their own session file; the reference model files are what the team needs to access.

• Trying to edit reference geometry directly: Objects linked through Worksession cannot be moved or scaled. Edit them in the source file.

• Expecting Undo to reverse a purge: Undo will not work; you need to activate another linked file or use Refresh All.

• Using Import, Insert, and Worksession for the same purpose: Merging files, adding content as blocks or groups, and working with references are different workflows.

Deciding on these distinctions at the start of a project clarifies file ownership and work boundaries. Worksession is useful because it lets you use different model files in the same working context without merging them into one file; team efficiency depends on file access, active model selection, and careful reference management.