Roblox animation and characters

Target line: Roblox Studio (October 2026 build) on macOS, driven through the scenario-roblox-expert toolkit.

Expert level here means every clip, layer, IK chain and face is proven in Studio by numbers: which track wins each joint, when each marker fires, what the server sees, and that the stepped pose matches its source. An agent cannot drive the Animation Editor, so it builds clips in code, steps them in Edit, plays them in a playtest and measures joints and tracks before it calls anything done. If a sibling skill named here is missing from your available skills, ask the user to install it (npx skills add scenario-labs/skills --skill <name>); unattended, proceed from tool schemas and flag the gap.

REQUIRED BACKGROUND: scenario-roblox-expert (channels, review loop, toolkit, current-Roblox traps).

Stance (the expert delta)

1. Avatar joints are AnimationConstraint, not Motor6D. The Avatar Joint Upgrade made R15 C0 and C1 read-only (L1, L8). Procedural motion multiplies into Transform in PreSimulation, which applies as a deferred batch and does not replicate (Suphi Kaner, BRYp2-rdpXQ 00:00:33). Code that looks joints up must accept both classes.
2. Load through the Animator, from the side that owns the rig. The owning client plays its character's tracks and the server sees them (L6); the server plays NPC tracks and clients see them (L7). Humanoid:LoadAnimation is deprecated.
3. Priority partitions joints; keys claim them. A higher priority wins only the joints it keys, and an identity key still claims its joint (L4). In clips built in code, parent Poses that are only on the path need Weight 0, or they override lower tracks [added] (L4).
4. Time gameplay with markers, never waits. Use one event name with a parameter (Develuper, d5GGIJJyMpg 00:02:52). GetMarkerReachedSignal fired within one frame (L6); KeyframeReached needs named keyframes (BrawlDev, zSK7bOoxuig 00:25:25).
5. Faces play as clips, not property writes. On a player's dynamic head, a FaceControls write or a finished tween reverts to 0 within 0.5 s, even with every track stopped [added] (L10, L16). A face clip holds, replicates, and survives the mood animation.
6. IKControls are created on the server; look-at weight is 0.999. At weight 1 the neck twists when the target passes behind; IKControl.Priority orders the solves; Pole is set from code (Suphi Kaner, 8fV-XOOj6O4 00:18:56, 00:53:00, 00:54:40).
7. Blender clips are 24 fps, armature only, no scale keys. Leaf bones, NLA strips and All Actions go off; Force Start/End Keying and Simplify 0 stay on (Mykaiju, NI7GXKLwk6U 00:23:45 to 00:27:07). 60 fps doubles the keys for no gain in gameplay (Nisky, EM9u4gIHoRg 00:07:55).
8. Temporary ids are test fixtures. RegisterKeyframeSequence hashes and active:// ids work in Studio only; the shipped game references published rbxassetid:// ids owned by the experience owner (Animation Editor docs).

Establish first

• Rig kind. R15 avatar (AnimationConstraint, BallSocket limits), custom part rig (Motor6D), skinned mesh (Bones), or AnimationController creature. Run P1 instead of guessing.
• Who plays what. Player clips on the client, NPC clips on the server, cosmetic layers locally.
• Server Authority. When on, an Animator keeps at most 8 active tracks, and tracks are looked up each tick with GetTrackByAnimationId, never cached.
• Character Controller Library. When on, movement comes from ControllerManager and abilities; ability callbacks never yield.
• Faces. Is there a dynamic head (Head has FaceControls)?
• Motion source. Blender FBX, a Scenario-generated rig or motion, the Animation Editor, or code.
• Publishing owner. User or group; clips must be published under the experience owner.
• Defaults: R15, Action for gameplay clips, Idle and Movement for locomotion, 24 fps, markers named after the event with a parameter.

Procedure

Code for every step is in references/procedures.md (P1 to P15), with the test that ran it and its numbers.

1. Inspect the rig (P1). Run AnimRig.joints, AnimRig.tree and AnimRig.path on the model. GATE: joint classes are known, every animated part has a path from the root, and an Animator exists.
2. Build or bring the clips (P2, P3, P10). Code clips use AnimClip.keyframes or AnimClip.curves, are registered with AnimClip.register and loaded with AnimClip.load, which waits for Length > 0. Blender clips go through blender_roblox_anim.py (audit, export, sample) and AnimClip.fromSamples. GATE: stepped joint angles match the keys within 0.3 degrees; Blender bone tails match within 0.01 studs.
3. Layer and time (P4). Set priorities, weights and fades; key only the joints each clip owns; put markers on contact frames. GATE: AnimClip.tracks(animator) shows the intended winner per joint, and each marker fires once per cycle.
4. Preview in Edit (P5). Call AnimClip.settle first: a clip that ended on its own still blends into the next one (P3). rbx_animation.pose_sheet steps a track with Animator:StepAnimations, captures each time and builds one contact sheet. GATE: read the sheet; the frame differences are above zero; AnimRig.reset leaves no posed joint before the place is saved.
5. Playtest (P6, P8). Play player clips from the client and NPC clips from the server; read the joints on both sides. GATE: the server finds the client's track, both sides report the same joint angle, and a capture shows the pose.
6. Layers, IK and faces (P9, P12, P7). Procedural offsets go into Transform in PreSimulation and skip when Animator.EvaluationThrottled is true. IK comes from AnimIK.reach and AnimIK.lookAt; faces from AnimFace.clip. GATE: the measured neck yaw, IK gap and face values on the server, plus a capture each.
7. Defaults and audit (P13, P14). Replace default animations through the Animate values; run AnimAudit.all. GATE: no error or warning finding; after a state change the client plays the new clip, checked by Length and joint angle, not by id.
8. Publish list. List every clip to publish, its priority, loop and markers, and the owner. GATE: no temporary id in shipped code (AnimAudit rule temp-animation-id).

Numbers

Value	Number	Relative to
Priority order	Core < Idle < Movement < Action < Action2 < Action3 < Action4	Enum.AnimationPriority
Default Animate tracks	idle at Core, mood at Idle	L6, player avatar
Fade	Play(0.4) ramps weight 0.25 per 0.1 s	L4
Same-priority blend	weighted mean: 90 and 60 degrees give 75 at equal weights, 84 at 1 and 0.25	L4
Action at weight 0.5 over Idle	60 degrees between 90 and 30	L4
Marker at 0.25 s of playback	fired at 266 ms, frame 16.3 ms	L6, speed 2
Stopped and Ended	500 and 816 ms for a 0.5 s playback	L6
Natural end, then a new clip	old pose blends in for 0.25 to 0.375 s (31.8 instead of 22.5 degrees at 0.25 s)	L3
First load	Length 0 at LoadAnimation, 14 ms to load in Edit	L2
Neck layer of 45 degrees	41.9 degrees on the joint, head 45.5 degrees off the root	L8
IK reach	hand 0.20 to 0.23 studs from a reachable target within 0.1 s, same on the client	L9
IK limits	4.17 studs from an unreachable target; 1.13 at Weight 0.5	L9
IK SmoothTime 0.5	gap 1.81 to 0.37 studs over 0.6 s	L9
Look-at	Weight 0.999; head within 0.05 degrees of the target	L9; Suphi Kaner
Face write or tween	back to 0 within 0.5 s	L10
Face clip	JawDrop 0.55 on client and server; the open mouth shows in the capture	L10
Blender to Studio	worst bone-tail error 0.0002 studs, 10 bones, 25 frames	L12
Skin weights	at most 4 influences per vertex	skinning docs
Server Authority	at most 8 active tracks per Animator	Server Authority docs
Dynamic head	4,000 triangles; validation checks 5 animations from 17 FACS poses	specs; Roblox Learn, OwhkWzSBnf0

Quality gates

Measurable:

• AnimAudit.all(game) returns no error and no warning (P14).
• Every track the code plays reports Length > 0, the intended priority and WeightCurrent 1 at rest (AnimClip.tracks).
• Each marker the code listens to fires once per cycle at its time, within one frame.
• Server and client report the same joint angles for replicated tracks.
• Blender exports pass audit with no finding, and P10's tail error is under 0.01 studs.
• AnimRig.dirty is empty on every rig before the place is saved.

Visual (contact sheets of at most 1,600 px, rbx_review.contact_sheet):

• Pose sheet of each clip at 4 to 6 times: silhouettes read, arcs, no interpenetration, closed loop.
• Playtest captures: player clip, NPC clip, IK reach with the target visible, face close-up next to a neutral capture.
• Judge with references/critique.md.

Common mistakes

Mistake	Symptom	Fix
Clip at Core or Idle	plays but the default idle wins	Action for gameplay clips
Action clip keys the legs	legs freeze while walking	key only the joints the clip owns
Code-built clip with Weight 1 parents	upper body overrides idle and walk	Weight 0 on path-only Poses (AnimClip.keyframes)
Playing right after a fresh register	nothing moves, Length 0	AnimClip.load waits for Length > 0
C0 writes on avatar joints	"Property is read only"	multiply into Transform in PreSimulation
FindFirstChildOfClass("Motor6D") on R15	nil on upgraded avatars	AnimRig.joint accepts both classes
Tweening FaceControls	expression flashes, then neutral	AnimFace.clip played on the Animator
task.wait for hit timing	hits drift with speed and lag	markers with parameters
Preview left posed in Edit	saved place shows the pose	AnimRig.reset(rig)
rig.HumanoidRootPart on a Custom skinned import	nil: the importer names the root RootPart (2 x 2 x 1), and bones never collide	AnimRig.prepareImport; clips authored before it still bind (references/characters.md)
Measuring right after another clip ended	first 0.3 s blends toward the old end pose	AnimClip.settle in Edit; deliberate fades in game
Checking a replaced default by its id	id matches while the old clip plays	check Length and the joint after a state change
60 fps or scale keys in Blender	heavy clips, scale ignored	24 fps, rotation and location only
LookAt Weight 1	neck twists when the target is behind	0.999
Shipping a temporary id	works in Studio, fails live	publish under the experience owner
Animator created on a client for a shared rig	others never see it	create it on the server

Handoffs

• Receives from scenario-roblox-assets: imported rigs and skinned meshes, including rigged characters and motions generated by scenario-3d. Motions arrive as FBX or Blender files and go through P10; rigs arrive as Models that P1 inspects.
• Delivers to scenario-roblox-gameplay: clips with markers at contact frames and their parameters; gameplay owns the hitboxes, state and NPC behavior that call them.
• Delivers to scenario-roblox-vfx-audio: marker names and times for footsteps, impacts and trails.
• Works with scenario-roblox-networking: look direction replication, Server Authority track rules, client-only cosmetic layers.
• Works with scenario-roblox-performance: Animator counts, NPC culling (anchor and disable Animators out of range, RDC 2025 rwLEnBtXr30 00:09:24), stepAnimation cost.
• Works with scenario-roblox-architecture: where animation controllers live (client modules for player characters, server services for NPCs).
• Asks the user to publish the listed clips; agents never upload.

Current Roblox notes

• Avatar Joint Upgrade: R15 avatars spawn with 15 AnimationConstraint joints and 14 BallSocketConstraints (L1).
• Workspace.AuthorityMode is not readable from plugin-level Luau (RobloxScript capability): ask the user whether Server Authority is on.
• Character Controller Library is opt-in. With it off, require("@rbx/AvatarAbilities") never returns on the client and returns a table on the server (L15).
• Adaptive Animation: HumanoidRigDescription:AutoRig needs RobloxScript capability; joint mapping and T-pose are set in the Adaptive Animation tool (GUI). Mapping joints from code did not retarget a clip onto renamed parts (L14).
• AnimationGraphDefinition exists; graphs are edited in the Graph Editor (GUI).
• The Animation Editor opens from Avatar > Clip Editor in the current UI.

References

• references/procedures.md: P1 to P15 with full code, test ids and results.
• references/characters.md: Custom skinned import to a rig, player and NPC playback scripts, creature foot planting, dynamic head cages and validation, FBX import checks, character cost.
• references/expert-notes.md: principles by expert, with timestamps.
• references/critique.md: the rubric for judging animation work.
• references/gui-paths.md: Animation Editor, import, faces and beta toggles for a human or computer-use agent.
• references/sources.md: every source with credentials and timestamps.
• scripts/rbx_animation.py: kit inlining, Blender wrapper, sample loader, Edit pose sheets.
• scripts/blender_roblox_anim.py: headless Blender test rig, audit, FBX export, re-import and samples.
• scripts/agentkit/animation/: AnimRig, AnimClip, AnimAudit, AnimIK and AnimFace Luau modules.