Freeform Align bends a floating object so that the points you pick on it meet matching points on a fixed object. Unlike Align Manually and Registration, which only move and rotate an object, Freeform Align changes its shape. Use it when the two objects really differ in shape, for example a warped or shrunk print against its CAD model, or a scan that is slightly bent.
You find the tool in Transform › Freeform Align.
When to Use Freeform Align
| Situation | Tool |
|---|---|
| The objects have the same shape but lie in different places | Align Manually for a rough fit, then Registration |
| Several scans of one object must fit each other | Global Registration |
| After a rigid fit, one object is still bent or stretched against the other in known places | Freeform Align |
First align the objects rigidly with Align Manually or Registration. Freeform Align should only correct the shape that remains different, not move the object across the scene.
Before You Start
- Select exactly two objects, each a mesh or a point cloud.
- The tool shows the object that is higher in the Scene tree as Floating (red): this object will be deformed. The other one is Fixed (blue) and does not change. Note that this is the opposite of Registration. Click Swap to exchange the roles.
- As in Align Manually, the viewport is divided into three areas: the floating object, the fixed object, and a preview with both.
Deform an Object Step by Step
- Select the two objects and go to Transform › Freeform Align.
- Check the names in Floating and Fixed; click Swap if needed.
- Click a point on the floating object, then the matching point on the fixed object. Each point gets a number, and points with the same number form a pair. The panel reminds you: Click on objects to setup points pair for adjustment.
- Add more pairs. Spread them over the whole object, especially over the areas that must change and the areas that must stay where they are.
- Set Adjustment Grid (see below).
- Click Apply. The floating object is deformed so that its points move to the matching fixed points. Apply becomes available once both objects have at least one point.
- Check the result in the preview. The pairs stay in place, so you can add more pairs and click Apply again. Delete All Points removes all pairs.
Apply changes the geometry of the floating object. To go back, press Ctrl+Z (Cmd+Z on macOS).
Adjustment Grid
The deformation is driven by a grid of control nodes placed around the floating object and the picked points. Adjustment Grid has three values: the number of nodes along X, Y and Z, from 2 to 9 each. The default is 5 × 5 × 5.
- Fewer nodes (2–4) give a smooth, overall correction, such as a slight bend or stretch of the whole part.
- More nodes (6–9) allow more local corrections. Use them with enough pairs spread over the object.
Start with the default and increase the values only if a local difference remains.
Typical Errors
- Areas without pairs change too. The deformation acts on the whole floating object, not only near the picked points. Add pairs on the areas that must stay where they are.
- The surface gets unwanted bumps between the points. Undo, lower the Adjustment Grid values or add more pairs, and apply again.
- The whole object jumps. The objects were not aligned rigidly before. Undo, align them with Align Manually or Registration first, then deform.
For several scans, Global Registration has a similar automatic step, Freeform Adjust, which needs no picked points.
