How to Use Rhino CageEdit: A Guide to Controlled Deformation

What will you learn in this guide?

In Rhino 8, the Cage and CageEdit commands let you change an object’s shape by editing the control cage around it, rather than moving individual control points. This method can be used for an overall shape adjustment or to affect a specific part of a model. When the cage’s control points are moved, captured objects deform accordingly.

This guide first covers the sequence for creating a control cage and linking an object to it. It then explains the cage type, accuracy, structure preservation, rigidity, and influence-area settings. The goal is to understand how each option affects the result when making a controlled shape adjustment to an architectural mass, interior element, or visualization model.

An important feature of CageEdit is that it deforms polysurfaces without separating their surfaces at the joins. The command also lets you select the control points of curve, surface, and mesh objects as captured objects. However, the result depends on the selected geometry and settings; the same number of control points or level of accuracy may not suit every model.

Requirements and preparation

The source documentation describes Rhino 8 commands. It does not specify separate account, plug-in, hardware, pricing, or licensing requirements for CageEdit. You can start in a Rhino project file with the object whose shape you want to change and a control object. The control object can be created with the Cage command or can be an existing curve or surface.

For an initial test, it’s helpful to choose an object whose response is easy to see and preserve the current state of the file. According to the Rhino documentation, CageEdit includes history information regardless of the History setting. Rhino 8 also includes the ExtractOriginalCaptives command, which restores a copy of the undeformed captured object at its original location without affecting the deformed object.

CageEdit workflow: step by step

1. Choose the object to edit. In the first step of CageEdit, select the object to deform—the captured object. Control points of curve, surface, or mesh objects can also be selected. The fact that surface joins on polysurfaces do not separate during deformation is worth noting when working with a unified model.

2. Create or select a control object. The Cage command creates a box-shaped cage for deforming other objects. In the command steps, you select the objects and then draw the cage box. In CageEdit, you can select an existing control object; the documentation notes that it may have been created with Cage or may be an existing surface or curve.

3. Set up the capture relationship with CageEdit. After selecting the objects to edit, select the control object that defines the region. You can then edit the control points of the cage. Clicking a cage control polygon selects two adjacent cage points; double-clicking selects a row of points. This selection behavior is useful when you want to make a change along a row rather than to individual points.

4. Assess the cage shape and point count. The cage can be a line, plane, or 3D cage based on the object’s bounding box. For box or rectangular cages, PointCount (XYZ) sets the number of control points in each direction, while Degree (XYZ) defines the degree in each direction. Entering a number at the Cage parameters prompt uses the same point count in every direction of a rectangular or box cage, with the degree options adjusted automatically.

5. Choose deformation accuracy. Accurate can slow updates and may produce denser surfaces when the deformed objects are refitted. Fast produces surfaces with fewer control points, but the result may be less precise. If responsiveness matters during an initial shape exploration, consider Fast; if shape accuracy is the priority, assess the effect of Accurate.

6. Check the structure-preservation and rigidity settings. PreserveStructure=Yes preserves the control-point structure of a curve or surface; if the object does not have enough control points, deformation accuracy may decrease. With No, the object can be refitted as needed to allow more accurate deformation. PreserveStructure does not apply to polysurfaces and is not shown when only polysurfaces are selected. Rigid changes the positions of captured objects without deforming their shapes. This setting applies per object; objects in a group are transformed as a unit. To change the rigidity state, recapture the objects with the same control object.

7. Set the influence area. Global does not limit the control object’s influence to the area inside the cage; objects that are partly inside the cage can also be deformed in their entirety. The effect may increase noticeably on objects farther from the control object. Local instead defines a Falloff distance around the control object. Objects or parts of objects beyond this distance are unaffected by the deformation. The falloff distance defines the area of full influence, the area with no influence, and the transition between them.

Common mistakes and things to watch for

Expecting the cage’s influence to stay inside the box: With Global, the effect is not limited to this area. Parts outside the cage may also change, and the result can be stronger than expected, especially on captured geometry farther from the control object. If you need to limit the effect, check the Local and Falloff distance options.

Mistaking a Fast result for final accuracy: Fast can produce surfaces with fewer control points and less precision. If the surface quality is insufficient, consider Accurate—but account for potentially slower updates and denser surfaces.

Looking for the PreserveStructure setting for every geometry type: This option relates to the control-point structure of curves and surfaces; it does not apply to polysurfaces. It is expected behavior for the setting not to appear when only polysurfaces are selected.

Assuming block instances will be deformed: According to the documentation, block instances always transform rigidly during CageEdit, regardless of the Rigid setting. Checking whether the elements to be deformed are block instances can help determine the expected result.

Worrying about losing the original geometry: In Rhino 8, ExtractOriginalCaptives restores the original captured object to its initial location when you select the control object; the existing deformed object is unaffected. This command can be used when comparing different shape explorations.

What does this mean for architectural and visualization workflows?

Architects, interior designers, and visualization artists can use CageEdit to change the overall proportions or a selected region of a mass, furniture form, or another part of a model. This is particularly useful when you want to work with a broader control area instead of manipulating individual model control points. The Local setting can help isolate the change from surrounding geometry, but the appropriate falloff distance should be tested based on the model’s scale and the intended effect.

The fact that polysurface joins do not separate can be useful for unified form adjustments. On the other hand, choosing between Accurate and Fast involves a trade-off between surface density and update speed. Because the documentation does not provide details about specific hardware, licensing costs, or compatibility with other software, you should also check the Rhino version and file workflow used in your project environment.

Next steps

After your first test, compare Local and Global on the same model, then examine how Fast and Accurate affect the surface. If the control-point structure matters, assess the PreserveStructure setting. When working with groups or block instances, keep rigid transformation behavior in mind. If you need to restore the original geometry, consult the Rhino 8 documentation for ExtractOriginalCaptives.

Sources and licensing

This guide is based on McNeel’s documentation for the CageEdit and Cage commands in Rhino 8. K1 and K2 are offered for free use on the source pages; the content has been retold in Turkish and adapted to the workflow.