Scenario Godot Animation

Godot animation (animator and technical animator)

Target: Godot 4.7.2.stable, macOS, Forward+ with Jolt Physics. Every procedure in references/procedures.md was run live in 4.7.2 on 2026-10-02 against a procedurally built humanoid, so nothing needs a download.

Stance

• Measure motion, do not eyeball it. A walk has one correct ground speed: the speed at which the planted foot stops sliding. Measure it from the clip (anim_motion.gd:foot_speed) and use that number for BlendSpace points and the controller. On a retargeted body the speed scales with Skeleton3D.motion_scale (a 1.15x body walked 1.38 m/s on a 1.2 m/s clip).
• Code decides, the animation layer presents. Gameplay owns velocity and state; the AnimationTree only reads them through advance expressions or parameters. The controller must still work with the tree removed (Fair Fight, jzuvd0Lstuw 00:05:46).
• Look at exact times. Seek or step to fixed times and open a contact sheet (gd_anim.pose_sheet). Real-time captures land on random frames.
• A layer must say which bones it owns. Partial clips do not stay partial: glTF export pads every clip with every animated joint, and an unfiltered OneShot under the default deterministic blending snaps every unlisted bone to RESET. Filters, not missing tracks, define layers.
• Choose the driver per motion. Velocity-driven locomotion with in-place clips keeps control responsive; root motion suits one-shot moves (dodge, climb, vault) where the feet must stay planted [added]. A tree suits a normal locomotion set; very large move sets or many procedural layers favor code plus SkeletonModifier3D layers (the experts disagree: Fair Fight against trees, xpoPfUKI9tw; RiftOfNostaria, Bitlytic and Chris for them). Tweens for runtime values with unknown starts, AnimationPlayer for authored multi-property curves (Queble, KUyQzjpRsU8 00:01:48).
• Silent failures are the norm here. A BoneMap naming bones that do not exist, an expression transition at advance mode Enabled, a missing RESET key: each produced no error in 4.7.2. Audit after every import and every tree change. 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.

Establish first

Ask once, then run:

1. Source of motion: Mixamo or other FBX, Blender glTF, mocap, hand-keyed in Godot, procedural only.
2. Rig: humanoid (SkeletonProfileHumanoid fits) or custom; T-pose or A-pose rest; real Root bone or not.
3. Locomotion model: velocity-driven (in-place clips) or root motion; target speeds if the design fixes them.
4. Layers needed: upper-body actions, aim or look-at, foot IK on uneven ground, hit reactions.
5. Characters sharing clips, and their height range.
6. Cutscenes: length, camera count, whether gameplay must be frozen, dialogue system in use.
7. Physics tick, renderer and target hardware (for IK and modifier cost).

Workflow with gates

1. Kit and project. gd_anim.install_animkit(P); confirm project.godot has Jolt for 3D and the brief's renderer. Gate: the kit's jobs return ok.

2. Import. Name cycles with a loop hint (Walk-loop), import once, then set options in the .import file (gd_anim.set_import_options, P3) and run --import. Turn on animation/import_rest_as_RESET. Gate: gd_anim.audit has no flags; every cycle loops; RESET exists.

3. Retarget. Build the BoneMap from the imported bone names (anim_import.gd:make_bonemap, P4); : becomes _ on import. Gate: skeleton is %GeneralSkeleton, bones renamed, sampled poses within 2 mm of the source.

4. Share. Import clips As Animation Library, give each body its own BoneMap, attach with anim_setup.gd:share_library (P5). Gate: 0 unresolved tracks, identical track layout.

5. Speeds. foot_speed per cycle and per body (P9). Gate: controller and BlendSpace speeds within 2 percent.

6. Tree. Build in code (anim_tree.gd, P6): BlendTree root, StateMachine inside, BlendSpace1D with sync, OneShot with a filter, TimeScale. Gate: drive with scripted input gives the expected state list and times; tree audit clean. The transition helper that passed the drive test:

   static func transition(expr: String, at_end: bool, xfade: float) -> AnimationNodeStateMachineTransition:
       var t := AnimationNodeStateMachineTransition.new()
       t.xfade_time = xfade
       t.advance_mode = AnimationNodeStateMachineTransition.ADVANCE_MODE_AUTO   # default Enabled never auto-fires
       if at_end:
           t.switch_mode = AnimationNodeStateMachineTransition.SWITCH_MODE_AT_END
       if expr != "":
           t.advance_expression = expr        # read on tree.advance_expression_base_node
       return t
   # sm.add_transition(&"Ground", &"Fall", transition("not on_floor and not jump_pressed", false, 0.2))

   Drive it from gameplay with tree.set("parameters/sm/Ground/blend_position", speed) and the state node's properties; fire actions with tree.set("parameters/act/request", AnimationNodeOneShot.ONE_SHOT_REQUEST_FIRE).

7. Layers and IK. OneShot filters (P7), FootPlacer plus TwoBoneIK3D (P10). Gate: foot within 2 cm of the target on a step, a hole and a 15 deg slope, read in skeleton_updated. Modifiers run in child order, so the placer (targets and hips) goes before the solver:

   var ik := TwoBoneIK3D.new()
   skeleton.add_child(ik)                       # after FootPlacer
   ik.setting_count = 2
   for i in 2:
       var side: String = ["Left", "Right"][i]   # := cannot infer from an array index
       ik.set_root_bone_name(i, side + "UpperLeg")
       ik.set_middle_bone_name(i, side + "LowerLeg")
       ik.set_end_bone_name(i, side + "Foot")
       ik.set_target_node(i, ik.get_path_to(targets[i]))
       ik.set_pole_node(i, ik.get_path_to(knee_poles[i]))      # 0.6 m in front of the knee
       ik.set_pole_direction(i, SkeletonModifier3D.SECONDARY_DIRECTION_PLUS_Z)
   skeleton.skeleton_updated.connect(_check_feet)   # final pose, after every modifier and influence

   Lower influence while running and set it to 0 in the air, so authored motion shows through (Lukky, MbaPDWfbNLo 00:09:30).

8. Camera and cutscene. SpringArm3D with a sphere shape (P12); one AnimationPlayer timeline (P13). Gate: call order and times, camera at checkpoints, animation_finished, section playback.

9. Look. Pose sheets: T-pose front and side, 8 walk phases, each state, IK terrain, cutscene timeline (P14). Gate: every sheet opened and described.

Expert checklist (state these in the plan)

• Modifier output is rolled back every frame (Fair Fight XFZQNsFejwk 00:02:04; P10 reads the animated pose a frame later). Fine for post effects; when modifiers own the pose, put pose_persist.gd with role RESTORE first and SNAPSHOT last: an incremental 5 deg modifier then reached 60 deg in 12 frames instead of staying at 5 (P16). RESTORE overrides the animation, so never use it on top of a playing clip.
• IK solves position only. TwoBoneIK3D left the foot 12.1 deg off a 15 deg slope; a CopyTransformModifier3D after it (rotation only, reference type Node, an align node with the ground tilt) brought it to 0.0 deg without moving the foot (P16; Lukky MbaPDWfbNLo 00:07:49).
• Deterministic IK solves from scratch each frame; a one-iteration chain needs the angle limit at the full 180 deg (Lukky 00:04:46). deterministic defaults to false on IterateIK3D; turn it on for stepping legs (MeroDev 17xi4vDqQJk 00:02:28).
• Bezier and property tracks cannot blend (docs): the tree blends value, position, rotation and scale tracks.
• Call Method tracks do not run in the editor preview (docs): test them in a run (P13).
• Capture update mode blends from the current value to the first key: a property at 5 with a key 10 at 0.5 s read 7.5 at 0.25 s under play_with_capture (P16).
• Cache find_track in a path-to-index map when scripts sample many tracks: Fair Fight measured 1.5 to 3x on large rigs (XFZQNsFejwk 00:04:03 to 00:06:45); on the 22-track test rig in GDScript, 1.2x (P16). It needs one track layout across clips, so turn off animation/remove_immutable_tracks.
• Gate one-shots on animation_finished plus a flag, or the next frame's locomotion call replaces the hit clip (DevWorm GMyw3eHDw7s 00:22:58). Measured: "hurt" held for its 0.4 s, then walk resumed (P16).
• Blender source. Rigify Limb Segments 1 and Game Friendly single root before export (CoderNunk 0wMONEpEXpQ 00:00:19, 00:01:23). nodes/apply_root_scale (default true) bakes import scale into meshes and clips, root stays at 1 (docs).
• BlendSpace2D for 4-way sprites: points at plus or minus 1, axis range plus or minus 1.1 so diagonals snap to left and right; 2D up is negative Y (Chris WrMORzl3g1U 00:09:20, 00:13:09).

Numbers