surface.md

title	surface / surfaces
description	Select finite surface references from a body or face model.
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head	tag content title surface / surfaces — Code3D TypeScript API reference

Select finite surface references from a body or face model.

Example

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

export const bodyS = box(20, 10, 14);
export const topFace = bodyS.surface(4);
export const endFaces = bodyS.surfaces([3, 4]);

Complete example: topology and references.

Signature

receiver.surface(id: SurfaceId): Surface;
receiver.surfaces(ids?: readonly SurfaceId[]): readonly Surface[];

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

Receivers and result

Solid and face models provide surface selection. Solid and Surface references provide their contained surfaces. Groups do not supply a shared surface numbering scheme. A selected Surface references a finite trimmed face; it does not create a FaceModel that can be extruded or thickened directly.

The example selects the unmodified box's S4, its +Y face, with area 280. Use its ID in shell to select an opening. Use the reference in align, wrap, directional bounds and measurement.

Surface properties

kind is surface and id is its SurfaceId. A surface is a FaceAnchor with center, area, flip(), six directional bounds, and vertex/edge/surface selection. Area measures only its finite trimmed region, subtracting holes.

flip() reverses normal sense for reference operations while keeping the finite geometry, position and reference axes. It does not construct a face model with reversed BRep geometry. See flip and reverse.

A Surface need not be planar. Geometry alignment uses the complete supporting surface and can ignore trimming; wrap instead requires its finite trimmed domain to contain the mapped layout. Use the model's plane reference when a planar constructor intentionally publishes an infinite plane.

IDs and selection order

IDs belong to the original geometry's topology namespace, not to an array index or the entire application. A valid ID is a positive integer or a readonly path of at least two positive integers. [1, 4] as a plural selection requests two IDs; [[1, 4]] requests one inherited path. Display labels such as E2 or S[1,4] are not accepted as string IDs.

Omitting the plural argument returns all available elements in topology order. An explicit ID array preserves authored order and duplicates. An empty array returns []. Malformed, unknown or retired IDs throw. Selecting through a child reference also checks membership: an ID elsewhere on the body cannot be selected through an unrelated surface or edge.

Child queries retain the original namespace rather than renumbering from one. Booleans and other construction operations may prefix inherited IDs with their input position; local edits preserve surviving IDs and retire replaced ones. Use the current result's topology after an edit. See topology lineage.