Advanced

Advanced

Deep‑dive mechanics, edge‑case tweaks, and performance guidelines for shipping projects.

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6.1 Axis Locks & Directional Hits

Concept

Axis locks zero‑out specific axes after the random / directional offset has been chosen. Use them to guarantee that a character never rolls upside‑down or that a turret stays level.

Workflow

1. In your ReactionProfile, set Rotation Axis Mask or Translation Axis Mask (values 0–1).

2. Toggle Use Local Hit Direction in BodyPartReactor to decide whether the mask is applied in bone‑local space (common) or world space (rare).

3. Combine with Use Contact‑Point Direction to switch between origin → bone vectors and projectile velocity.

Tip: For top‑down games, lock the Y rotation (pitch) so hits only spin characters on the Z‑axis.

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6.2 Follow‑Through Chains

Goal

Create natural secondary motion—gear, hair, or child bones lag behind the main impact.

Setup

1. On the primary BodyPartReactor (e.g., Chest) add followers:

   • Drag the Head bone into Follow Transforms list.

   • Follow Rot Weight ≈ 0.25, Follow Pos Weight ≈ 0.1.

2. On Head you can still keep its own reactor for direct hits.

Best Practices

• Chain order: torso → shoulders → head → props.

• Keep weights < 0.5 to avoid double‑moving (follower + self‑reactor).

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6.3 Slow‑Blend for Heavy Impacts

Enable Slow Blend Mode to multiply the profile’s Blend‑In Speed by Slow Blend Multiplier (0–1). This makes the reaction appear heavier without changing strength.

if (impactForce > 120f)
    chestReactor.slowBlendMode = true;
else
    chestReactor.slowBlendMode = false;

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6.4 Performance & GC

Concern	Recommendation
Per‑frame math	All trig done on 3–10 bones → sub‑0.1 ms on modern CPUs.
Garbage	Allocation‑free. Randoms use UnityEngine.Random.Range (no boxing).
Physics cost	System itself adds none; use primitive colliders and pooled projectiles to keep PhysX cheap.
Burst / DOTS	Not required—system is already CPU‑light, but you can port BodyPartReactor.Update() to Burst if profiling shows spikes.

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6.5 Networking / Determinism

Because the system is pure math on floats and doesn’t sample animation curves at runtime, reactions can be reproduced deterministically across clients.

1. Sync only these parameters on hit:

   • partName (string or enum)

   • hitDirection (normalized Vector3, 16 bits per component works)

   • hitPoint (optional—needed only if profile uses contact‑point direction)

2. On each client call React() with the same values.

3. Ensure all clients load identical ReactionProfile assets (GUID match). Prefer AssetBundles or Addressables to avoid mismatches.

Rollback netcode: Because reactions are purely cosmetic, you can skip rewinding bones—simply apply the hit on the presentation frame.

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6.6 Editor Automation & Gizmos

• Coming in a future update: Bone Auto‑Setup Wizard that scans your rig and adds reactors to common bones with a single click.

• Enable Gizmos to visualize hit directions and axis masks while tuning profiles in Play Mode.