Rhino 8 CageEdit Guide: Controlled, Smooth Model Deformation

Rhino 8’s CageEdit command lets you smoothly deform captured objects by editing the points of a control object. This guide walks through the Cage, CageEdit, and SoftEditCrv functions described in the official Rhino 8 documentation, for anyone looking to adjust an architectural or interior model globally or within a limited area. The commands are covered only within the scope of the options described in the Rhino 8 documentation; no single ideal cage density or falloff value should be assumed for a given model.

When to use CageEdit

CageEdit lets you make broader, smoother changes using a cage’s control points, rather than moving an object’s control points one by one. According to the Rhino documentation, this method can smoothly deform surfaces with dense control points. On polysurfaces, deformation does not separate the parts at their seams. The effect can extend across the entire object or be limited to a local area.

A control object can be created with the Cage command or be an existing curve or surface. A cage can be a 1D, 2D, or 3D structure, such as a rectangle or a line; its type depends on how it is created and on the object’s bounding box. The Rhino documentation notes that cages with a small number of control points can edit complex objects, with smoother transitions than standard control-point editing.

Deforming with CageEdit: step by step

1. Select the object to edit. The captured objects specify the geometry affected by subsequent cage edits. Curve, surface, or mesh control points can also be selected as captured objects.

2. Select or create a control object. To create a cage, use Transform › Cage Editing › Create Cage or the Cage command. Alternatively, you can use an existing curve or surface as the control object. The Rhino documentation says the cage box can be created relative to the object’s bounding box.

3. Start CageEdit and specify the control object. The command path is Transform › Cage Editing › Cage Edit. After defining the objects and control object, edit the control cage’s points.

4. Shape the edit using cage points. Clicking a cage control polygon selects two adjacent cage points; double-clicking a polygon selects a row of points. This selection behavior helps shape the deformation by applying it to a single point or a wider row.

5. Check the result and, if needed, release the object from the cage. ReleaseFromCage removes selected objects from the influence of the CageEdit control object. The documentation also lists SelCaptives, which finds captured objects associated with the control object.

Influence range and deformation options

Global and Local are two different approaches for defining the reach of the cage’s influence. Global affects objects throughout 3D space; parts of an object outside the cage can also be deformed. The documentation warns that the effect can grow significantly as objects extend beyond the control object. So don’t assume that only the region inside the cage will change.

The Local option defines a Falloff distance extending outward from the control object. Objects or parts of objects beyond this distance are unaffected by the deformation. The cage’s full-influence area, the unaffected area, and the transition between them work together. Local may be more suitable when you need to control where the effect starts and fades out, but the documentation does not recommend a specific numerical distance.

PreserveStructure does not apply to polysurfaces and is not displayed when only a polysurface is selected. Also, for a curve or surface, choosing Yes can reduce deformation accuracy if the object does not have enough control points. No allows the object to be refitted with more cage control points if needed for an accurate deformation. Block instances can be edited with CageEdit, but the documentation states that blocks are always transformed rigidly, regardless of the Rigid setting.

More local curve editing: SoftEditCrv

To smoothly edit an area around a specific point on a curve without using a cage, you can use SoftEditCrv. The command moves the selected point while gradually reducing the change along the curve as distance from that point increases. Select the curve’s edit point, specify a target location, and set the influence distance. Distance is measured in model units; you can enter a value or set the distance by clicking on the curve.

FixEnds=Yes keeps the ends in place, even if the Distance value exceeds the distance to one or both ends of the curve. However, the Rhino documentation notes that on dense curves, this setting can cause an abrupt change near the ends. With FixEnds=No, the ends are allowed to move if the distance extends to them. If the curve’s ends need to remain fixed, check the result of both behaviors carefully.

What to watch for in architectural and visualization workflows

CageEdit can change the overall form of a surface or polysurface without manually moving many individual control points. A Local influence range can be useful when nearby geometry needs to remain intact, while Global can affect a wider portion of the object. SoftEditCrv is another option when dense curves need a local adjustment.

In the workflow, it’s important to ensure that the selection and settings suit the geometry: Fast prioritizes update speed but reduces accuracy; Accurate may run more slowly. The source documentation does not specify hardware requirements, licensing terms, or performance measurements, so no specific hardware or cost conclusions can be drawn. After deformation, checking surface density, curve ends, and how geometry outside the cage was affected can help identify unexpected changes in shape.

Common mistakes

• Assuming that only the area inside the cage will change when Global is selected. Global can also affect areas outside the cage.

• Using Fast without accounting for the loss of accuracy. According to the Rhino documentation, Fast creates less accurate surfaces with fewer control points.

• Assuming that PreserveStructure=Yes will always provide the same accuracy. Too few control points can reduce deformation accuracy.

• Expecting the Rigid setting to change how block instances behave. The documentation describes blocks as objects that are always transformed rigidly.

• Overlooking how FixEnds=Yes affects the result near the ends of a curve in SoftEditCrv. Dense curves can show an abrupt transition.