FreeCAD MultiTransform: What It Is and How to Use It

This article provides a concise overview of the MultiTransform feature in FreeCAD's Part Design workbench, explaining what it does, why it is advantageous for parametric modeling, and how to apply it step-by-step. You will learn how to combine transformations such as linear patterns, polar arrays, and mirrors into a single operation, keeping your model tree clean and your workflow efficient.

What is the MultiTransform Feature?

The MultiTransform tool in FreeCAD allows you to apply multiple transformations—such as Mirrored, Linear Pattern, Polar Pattern, and Scaled—to one or more base features in a single, unified operation.

In standard workflows, applying a mirror, followed by a linear array, followed by a polar array creates three separate feature dependencies in the model tree. MultiTransform consolidates these sequential modifications into one container. This keeps the construction tree organized, reduces file complexity, and minimizes the risk of topological naming issues caused by deep dependency chains.

Available Transformation Types

Within a single MultiTransform container, you can add any combination of the following operations:

  • Mirrored: Reflects the feature across a designated plane or face.
  • Linear Pattern: Duplicates the feature along a specified direction vector with defined spacing and occurrences.
  • Polar Pattern: Rotates duplicates of the feature around an axis over a defined angle.
  • Scaled: Changes the size of the feature relative to a center point (used less frequently, but available for specific geometric needs).

How to Use MultiTransform in FreeCAD

Follow these steps to set up and configure a MultiTransform operation:

1. Create and Select the Base Feature

Ensure you are in the Part Design workbench. You must have an active Body containing a base solid and a feature you want to duplicate (such as a Pocket, Pad, or Hole). Select the feature in the tree view or in the 3D viewport.

2. Activate the MultiTransform Tool

Click the Create a MultiTransform icon on the Part Design toolbar (or select Part Design > Apply a pattern > MultiTransform from the menu).

3. Add Transformations

Once the MultiTransform task panel opens on the left:

  1. Locate the Transformations box in the Task panel.
  2. Right-click inside the blank area of the box.
  3. Select the first transformation type you wish to apply (e.g., Add Linear Pattern).
  4. Configure the parameters for this pattern (e.g., direction, length, number of occurrences).

4. Chain Additional Transformations

To apply subsequent transformations:

  1. Right-click inside the Transformations list again.
  2. Select the next transformation (e.g., Add Polar Pattern).
  3. Set the axis, angle, and number of occurrences. The second pattern will act upon the results generated by the first pattern.
  4. Repeat this process for as many operations as required.

5. Adjust Order and Finalize

The sequence of transformations matters, as each step operates on the outcome of the preceding step:

  • To change the execution sequence, right-click an item in the list and select Move up or Move down.
  • To remove a step, right-click and choose Delete.
  • Once the preview in the 3D view is correct, click OK to apply the transformation.

Key Considerations

  • Order of Execution: Applying a Linear Pattern before a Polar Pattern yields a very different geometry than applying a Polar Pattern before a Linear Pattern. Plan the geometric hierarchy before adding steps.
  • Overlapping Geometry: Ensure that duplicate features do not create non-manifold intersections, which can cause the Part Design engine to throw an error.
  • Performance: Complex combinations involving large numbers of instances can increase recomputation time. Test patterns with smaller instance counts before scaling up.