t1k:unity:base:pivot-hierarchy

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Field	Value
Module	base
Version	2.2.2
Effort	medium
Tools	—

Keywords: hierarchy, pivot, transform, unity

How to invoke

/t1k:unity:base:pivot-hierarchy

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Unity Pivot & Hierarchy Patterns

Guide for the “empty parent + offset child” hierarchy pattern. Applies to pivot fixing, rotation pivots, orbits, attachment sockets, animation isolation, and DOTS ECS baking.

Scope: GameObject hierarchy restructuring for pivot control. Does NOT cover animation rigging, IK solvers, or physics joints.

Core Concept

1. Create empty parent GO at logical position (feet, rotation center, socket)
2. Add child GO with mesh/visual at calculated offset
3. Parent controls world position/rotation; child controls visual offset

Root (empty)          ← position = feet / rotation center / socket
  └─ Mesh (child)     ← localPosition = (0, offset, 0), has MeshFilter + MeshRenderer

Offset Calculation Reference

Unity built-in primitive half-heights at scale 1:

Primitive	Height	Half-Height	Offset Formula
Capsule	2m	1.0	1.0 * scale.y
Cylinder	2m	1.0	1.0 * scale.y
Cube	1m	0.5	0.5 * scale.y
Sphere	1m	0.5	0.5 * scale.y
Custom mesh	varies	bounds.extents.y	mesh.bounds.extents.y * scale.y

Scale goes on child, not parent. Offset in parent-local space.

DOTS Critical Gotchas

• PostTransformMatrix conflicts with TransformBaker — adding manually in a custom baker causes entity count drops and broken SubScene loading. Only use via TransformUsageFlags.NonUniformScale.
• “Fix the data, not the code” — restructure the prefab hierarchy rather than compensating in runtime systems.
• += offset accumulates per frame — use = (absolute) or fix in prefab.

→ Full use cases (A-F), DOTS baking behavior, ECS parent-child setup, decision framework: references/use-cases-and-ecs.md

Reference Files

File	Contents
use-cases-and-ecs.md	Use cases A-F with code, DOTS baking, ECS gotchas, decision framework