Rhino 8 CageEdit Guide: Controlled Deformation for Architectural Models

Rhino 8’s official documentation describes CageEdit as a tool for smoothly shaping models by editing the points of a control cage. It works with two- or three-dimensional control objects and can apply changes to an entire object or limit them to a specific region. The steps, options, and usage notes below are based on the Rhino 8 documentation.

What can CageEdit be used for?

CageEdit lets you change a model’s shape by moving the points of a control object, rather than editing the geometry’s individual control points. Create a control object with the Cage command, or select an existing curve or surface for this purpose. You can also use an edge of the same object or a face of a polysurface as the control object.

The command also supports selecting the control points of a curve, surface, or mesh as captives. When polysurfaces are deformed, their surfaces remain joined at the edges. CageEdit creates editing history regardless of the History setting.

The documentation notes that a cage with a small number of control points can be used to modify more complex objects. Compared with standard control-point editing, this approach can provide smoother transitions. The result depends on the cage structure and the selected deformation options, so it’s worth testing on a representative copy before using it on production geometry.

Creating and editing a cage: step by step

1. Select the geometry to capture. In CageEdit, select the objects whose shape you want to change as the geometry that will be affected by the control object. You can also select the control points of a curve, surface, or mesh as captives.

2. Create or select a control object. To create a new cage, run the Cage command, select the objects, press Enter, and draw the cage box. Alternatively, use an existing curve or surface as the control object. A control object created with BoundingBox can be a line, plane, or three-dimensional cage, depending on the bounds of the input geometry.

3. Set the cage’s point count and degree. PointCount (XYZ) sets the number of control points in the different directions of a line, rectangle, or box. Degree (XYZ) specifies the cage’s degree in those same directions. Entering a number at the “Cage parameters” prompt applies an equal point count to all directions of a rectangle or box; the degree settings are adjusted automatically.

4. Edit the cage points. Clicking a control polygon selects two adjacent cage points; double-clicking selects the points in a row together. Move the selected points to shape the captured geometry.

5. Choose the deformation type and scope. Is the goal to preserve the surface structure, get a result with fewer control points, or limit the area of effect? The table below summarizes the options described in the documentation by use case; it does not recommend universal default values.

PreserveStructure applies to the control-point structure of curves and surfaces; it is not available when a polysurface is selected. Rigid changes the position of a captive without changing its shape. This setting works on a per-object basis; the same control object can affect some objects rigidly and others non-rigidly. To change an object’s rigid behavior, capture it again with the same control object. Objects within a group transform as a whole. Block instances preserve their shape and transform rigidly, regardless of the Rigid setting.

How do Global, Local, and Falloff distance work?

Global does not limit the control object’s effect to geometry inside the cage. Even if only part of an object is inside the cage, the change can extend to the rest of the object. The effect can also grow on objects farther from the control object. As a result, Global may produce unexpected results when you want to modify only a limited section.

The Local option lets you define a Falloff distance around the control object. It creates a transition between the region where the cage has full effect and the area where it has no effect; objects or parts outside the falloff distance are unaffected. You can also define a sphere, cylinder, or box to constrain the effect to a specific volume around the object. This gives you greater control over where the deformation is applied to the model.

For a two-dimensional object, ObjectPlane aligns the rectangular cage with the object’s orientation in 3D space. If the cage is no longer needed, ReleaseFromCage removes the selected objects from the control object’s influence. SelCaptives helps select objects linked to a specific control object. Listed as new in Rhino 8, ExtractOriginalCaptives restores the original, undeformed object to its initial position without affecting the deformed object. The Explode command converts the control object into normal geometry.

In architecture, interiors, and archviz workflows

CageEdit can be useful when a larger shape change is needed for a massing model, facade surface, or interior element. The fact that polysurfaces remain joined at their edges can be helpful when working with multi-surface models. However, keep in mind that block instances do not stretch when edited with a cage.

In offices, comparing Global and Local on a copy of the model first can help confirm that the change stays within the intended area. When choosing a setting, also consider that Accurate can slow updates, while Fast may produce surfaces with fewer control points and less accuracy. The documentation does not specify hardware requirements, pricing, or licensing terms; check these separately for the Rhino version and license you use.

Common mistakes

• Assuming Global means a local effect: Geometry outside the cage may also change, and the effect may grow with distance.

• Expecting the highest accuracy from Fast: This option creates surfaces with fewer control points, and the result may be less accurate.

• Looking for PreserveStructure on a polysurface: This option is not shown for polysurfaces.

• Assuming block instances will stretch: These instances always transform rigidly during cage editing.

• Leaving the control relationship in place: Use ReleaseFromCage to remove objects from the cage’s influence.