shell.md

title	shell
description	Hollow one connected solid with signed wall thickness and optional openings.
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head	tag content title shell — Code3D TypeScript API reference

Hollow one connected solid with uniform walls. Choose input surfaces as openings, or create a fully enclosed cavity.

Example

import {box} from '@code3d/core';

export const enclosure = box(40, 24, 30).shell(1.5, [4]);

Complete example: solid operations.

Signature

model.shell(
  thickness: number,
  removedSurfaceIds?: readonly SurfaceId[],
): SolidModel<Elements>;

Import the functions and named types from @code3d/core.

Parameters and result

Parameter	Meaning
thickness	Finite nonzero signed wall thickness in model units
removedSurfaceIds	Optional array of input surface IDs to remove as openings

Positive thickness offsets the walls inward, preserving the outside dimensions. Negative thickness offsets outward, retaining the input boundary on the inside; separating offset faces use rounded joins. Omit the second argument or pass [] for a fully enclosed cavity. The App editing default is 1, but TypeScript requires an explicit thickness.

S4 is the unmodified box's +Y face, so the example is open at the top. Its outside bounds remain [-20, -12, -15] to [20, 12, 15]. The bottom and side walls are 1.5 units thick. The method returns a new solid without modifying the box.

Choosing openings

Use IDs from the input solid. IDs are positive integers or paths of at least two positive integers. [4, 6] lists two surfaces; [[1, 4]] lists one inherited surface. Duplicates are resolved once in input order. Unknown or retired IDs throw, and removing every face is invalid: at least one face must remain a wall.

The result retains the input local frame, placement, material and exposed interface. One-to-one inherited topology keeps its complete ID. New offset walls receive new IDs; pick later fillet or chamfer selections from the shell result. Exposed topology references remain useful only while their selected topology survives. See topology IDs.

Limits and alternatives

A shell requires exactly one connected solid. A disconnected union cannot be hollowed as one body. Narrow features, tight curvature, excessive thickness or interacting offsets can prevent a valid cavity. Failed construction throws; errors include the thickness and selected openings.

Some mixed-profile lofts can enclose a cavity but fail when an end is opened, even at smaller thicknesses. Reducing thickness alone does not always resolve unsupported geometry. Change the openings or simplify the source solid. The kernel checks for a valid solid with a cavity and, for open shells, generated wall faces.

Use thicken to build a solid from a face rather than hollowing an existing solid. For the App's opening selection controls, see making hollow parts.