origin-point.md

title	originPoint
description	Choose a point reference as the local origin of a model or group.
sourceReview	packageVersion sources 0.0.1-alpha.16 path sha256 packages/core/src/library/runtime.ts dcee3d2388a9b7b3819bb4897edd894463daa0e5b519e832a3349fac98c3bff8 path sha256 commit packages/core/src/library/spatial.ts 810c4fa69352c26c32fb04a0e7867f6327698e02f3212669f17d777784322a78 69d231fb775befdb3cd098291b4097ccd52d8966
sidebar	hidden true
head	tag content title originPoint — Code3D TypeScript API reference

Make an existing point reference the local zero of a model or group.

Example

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

const path = line([10, 0, 0], [30, 0, 0]);
export const midpointZero = path.originPoint(path.midpoint);

Complete example: origins and local transforms.

Signature

model.originPoint(point: PointAnchor): ModelForKind<Elements, Kind>;

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

Selecting the point

point must be a point reference: a model's origin or center, a vertex, a curve's start, midpoint or end, an exposed point, or a point model. Raw coordinate arrays are not accepted; use originOffset for a numeric displacement. A non-point reference throws.

The reference is resolved into the receiver's local coordinates. The example's midpoint is [20, 0, 0], so the resulting endpoints are [-10, 0, 0] and [10, 0, 0]. Curve length remains 20.

A carried center is a stable reference transformed with the model; it may differ from the current axis-aligned bounding-box center after rotation or geometry editing. Select model.center deliberately, or use originCenter to recompute the bounding-box center.

Selecting inside groups

Groups support this method without inventing an aggregate vertex numbering scheme. Use a member's actual instance point, or an exposed point reference. Nested instances are resolved in the group frame. Repeated use of the same source can make a bare reference ambiguous; select a specific occurrence. The whole assembled layout is rebased together.

Value and reference behavior

The operation returns a new model with the same kind and exposed member types. The original value and previously selected references keep their meaning. Topology IDs are preserved. Geometry and named references are transformed together; model.origin and model.frame.origin on the result still refer to its local zero. Origin changes preserve directions, lengths, areas and volumes.

These operations work in the receiver's local coordinates. A relation's offset places a part in a composition; it is a separate operation. For an already related model, its own geometry references in stored placement conditions are transformed consistently. See local coordinates for assembly frame rules.