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Programming Bible

Sequencer Foot Placement — MetaHuman on uneven terrain

Status: Active tutorial · 2026-11-09
Products: Standalone cinematic level (primary) · Cinematic Benchmark showcase path · reusable Level Sequence takes
Authority: CB 28 · howto 29
Not this doc: Gameplay Pose Search / Motion Matching — motion-matching-demo-and-full.md

Hard lock — no Motion Matching in the cinematic: This tutorial is foot placement only. Do not wire Pose Search, Character Trajectory, or a loco pose database for the Level Sequence. Clip choice and blends live in the Animation Mixer; ground conform lives in the Foot Placement node on the MetaHuman body AnimBP.

0. Goal

Section titled “0. Goal”

Get flawless, ground-conforming feet for a MetaHuman walking an uneven outdoor landscape inside an Unreal Level Sequence, using:

  1. Foot Placement IK in the MetaHuman body AnimBP (landscape collision traces).
  2. Animation Mixer tracks in Sequencer (not the legacy Animation track).
  3. Sequencer flags so AnimBP + post-process evaluate while scrubbing/playing.
  4. Mixer bone matching to kill horizontal foot slide on clip cuts.
  5. Optional additive polish for harsh ledges.
Layer Owns Must not own
Mixer base layer Loco clips — root motion walks / runs / idles that move the character Upper-body gesture choice
Mixer upper layers Arm / torso / look blends — not required to be root motion Root translation authority
Foot Placement (body AnimBP) Ankle / pelvis adjust to landscape collision Clip choice
Anim Instance track flags Evaluate AnimBP + post-process in Sequencer Replacing Mixer
Additive Mixer layer Shot-specific foot/Control Rig keys Replacing Foot Placement entirely

Baked full-body Animation tracks that disable the AnimBP kill ground IK. Legacy Animation track on the Body mesh is the usual failure mode.

1. Phase 1 — Foot Placement in the MetaHuman AnimBP

Section titled “1. Phase 1 — Foot Placement in the MetaHuman AnimBP”

By default, Sequencer-driven clips do not “see” world geometry. Put a Foot Placement node in the MetaHuman’s primary body skeletal AnimBP so legs line-trace against landscape collision and adjust procedurally.

  1. Open the MetaHuman body Animation Blueprint

    • Typical path: Content / MetaHumans / [YourMetaHumanName]
    • Open the main body skeletal AnimBP (often Abp_MetaHuman or similar).
    • Do not put this node only in the Post Process AnimBP — Foot Placement belongs on the primary body graph that feeds the output pose (post-process still evaluates for muscle/clothing; see Phase 3).

  2. Open the AnimGraph.

  3. Right-click empty grid → search Foot Placement → place the node.

  4. Wire it immediately before the final output:

[Core motion / Mixer-driven pose]  →  [Foot Placement]  →  [Output Pose]
  1. Select Foot Placement → Details → MetaHuman bone hierarchy:
Property Value
IK Foot Root ik_foot_root
Pelvis Bone pelvis

Leg Definitions — add two rows:

Leg FK Bone IK Bone Ball Bone
Left foot_l ik_foot_l ball_l
Right foot_r ik_foot_r ball_r
  1. Plant Settings (same node):
Property Value Why
Speed Threshold 10.0 Treats slow foot as planted
Unplant Radius 20.0 Smooth unlock as the step leaves
Max Offset 250.0 Reach into deep dips
Pelvis Adjustment Strength 1.0 Hips drop with the stretch; reduces knee pop / rigid lock
  1. Compile and Save the AnimBP.

Verification: Landscape (or mesh) under the route has collision. Foot Placement traces collision, not Nanite visual tris alone.

2. Phase 2 — Sequencer Animation Mixer

Section titled “2. Phase 2 — Sequencer Animation Mixer”

The legacy Animation track overrides character blueprints aggressively and often disables ground IK. Use the Animation Mixer track so Sequencer clips and the AnimBP (Foot Placement) coexist.

Mixer reference (full walkthrough): Animation Mixer in Sequencer (YouTube) — use this for every Mixer UI aspect (layers, clips, blends, matching). This chapter locks what we put on each layer for Terra Firma cine feet; the video shows how to operate the Mixer.

2.1 Base layer = root motion

Section titled “2.1 Base layer = root motion”

On the Mixer base layer, use root motion animations for locomotion (walk, run, stop, turn-in-place with authored root, etc.). The base layer owns world travel of the MetaHuman through the shot. Non–root-motion loco on the base layer is what causes skate that Foot Placement cannot fully hide.

2.2 Upper-body layers = not root motion

Section titled “2.2 Upper-body layers = not root motion”

Add another Mixer layer (or layers) for upper-body blends — arms, torso, look-at, prop holds, dialogue gesture. Those clips do not need root motion. Keep root translation on the base layer only so upper blends cannot fight or double-drive the root.

Mixer layer Clip type Root motion?
Base Loco / travel Yes — required
Upper (additive or layered blend) Arms / torso / face-adjacent body No — not required; prefer non–root-motion
Additive polish (Phase 5) Per-shot foot / Control Rig keys N/A (keys, not loco clips)

2.3 Wire steps

Section titled “2.3 Wire steps”
  1. Edit → Plugins → search Sequencer Mixer → enable → restart editor if prompted.
  2. Open the Level Sequence → drag the MetaHuman blueprint actor onto the timeline.
  3. Under the MetaHuman hierarchy: if a legacy Animation track auto-spawned on the Body mesh component, delete it.
  4. On the Body component layer → green + Track.
  5. Animation → Animation Mixer.
  6. On the base layer: right-click → add root motion loco clips (walk, run, idle-with-root as authored).
  7. Add an upper-body layer on the Mixer → place non–root-motion upper clips; blend/weight per the Mixer video above.
  8. Do not put traveling root motion on the upper layer.

Verification: Body has an Animation Mixer (no legacy Animation track); base clips are root motion; upper layer blends without moving the root.

3. Phase 3 — Evaluate AnimBP + post-process in Sequencer

Section titled “3. Phase 3 — Evaluate AnimBP + post-process in Sequencer”

MetaHumans use a secondary post-process layer (muscle, clothing, tissue). Sequencer needs explicit permission to run landscape traces and that stack while scrubbing.

  1. On the MetaHuman Body component track → + Track → Anim Instance.
  2. Right-click the Anim Instance track → properties → enable:
    • Evaluate Post Process Blueprint = True
    • Update Animation in Sequencer = True
  3. Scrub the playhead: feet should pitch/yaw and conform to slopes, rocks, and uneven landscape in real time.

Verification: Scrub shows live Foot Placement; if feet stay flat to the clip only, Anim Instance flags or Mixer vs legacy track are wrong.

4. Phase 4 — Kill horizontal slide (Mixer bone matching)

Section titled “4. Phase 4 — Kill horizontal slide (Mixer bone matching)”

Phases 1–3 lock feet to slopes vertically. Crossfades between Mixer clips can still slide horizontally. Fix inside the Mixer timeline:

  1. Place clip A, then clip B (slight overlap if you want a crossfade).
  2. Scrub to the first frame where clip B begins.
  3. Right-click clip B → Match With This Bone In Previous Clip.
  4. Pick the weight-bearing foot (foot_l or foot_r).
    • Mid-sprint / leap with no clean plant → match pelvis for velocity continuity instead.
  5. Enable Match X and Y Translation so world-space speed stitches across the cut.

Verification: Transitions no longer skate the planted foot across the dirt.

5. Phase 5 — Additive cinematic polish

Section titled “5. Phase 5 — Additive cinematic polish”

For a steep hill or rocky ledge where Foot Placement is correct but the ankle looks wrong for one shot:

  1. On the Animation Mixer track → + Track → Additive Layer.
  2. Select the offending foot bone or MetaHuman Control Rig handle on that frame.
  3. Adjust/rotate in the viewport → keyframe.

The Mixer blends artistic keys on top of automated terrain alignment. Do not turn Foot Placement off “to stop jitter” — fix collision, plant settings, or add a short additive key.

6. Authoring checklist (standalone cine level)

Section titled “6. Authoring checklist (standalone cine level)”
  1. Standalone cinematic map + MetaHuman placed.
  2. Body AnimBP: Foot Placement wired before Output Pose · plant settings set · compile.
  3. Landscape collision under the path.
  4. Level Sequence: MetaHuman bound · no legacy Body Animation track.
  5. Animation Mixer: base = root-motion loco · upper layer(s) = non–root-motion blends (Mixer video).
  6. Anim Instance track: Evaluate Post Process + Update Animation in Sequencer.
  7. Bone-match weight-bearing foot (or pelvis) on clip cuts.
  8. Optional additive keys for harsh frames.
  9. Scrub + PIE: feet conform; no Pose Search / MM required for this take.

7. Acceptance

Section titled “7. Acceptance”
AC Pass
Vertical plant Feet pitch/yaw to landscape collision while scrubbing Sequencer
Mixer Clips driven by Animation Mixer, not legacy Animation track
Root motion Base layer loco clips are root motion; upper layers are not
Post-process Anim Instance evaluates post-process + updates anim in Sequencer
Horizontal Clip cuts bone-matched; no skate on plant foot
No MM Cine take does not depend on Pose Search / trajectory DB
Collision Route has walkable collision under uneven visuals

8. Anti-patterns

Section titled “8. Anti-patterns”
Don’t Do
Legacy Animation track on Body Animation Mixer
Non–root-motion walk/run on Mixer base Root-motion loco on base only
Root-motion travel on upper-body Mixer layer Upper layers = non–root-motion blends
Pose Search / MM “for cinematic feet” Foot Placement + Mixer clips
Foot Placement only in Post Process, skipped primary graph Primary body AnimGraph → Foot Placement → Output
Rely on Nanite tris as trace targets Landscape / mesh collision
Disable Foot Placement to fix one bad ankle Additive Mixer layer on that frame
Expect Mixer crossfade alone to fix world-space slide Match With This Bone + Match X/Y

9. Troubleshooting

Section titled “9. Troubleshooting”
Symptom Check
Feet ignore terrain Foot Placement in primary AnimBP? Anim Instance flags on? Legacy Animation track deleted?
Vertical OK, horizontal skate Bone match on clip B; Match X/Y; correct plant foot
Knee pop / rigid stretch Pelvis Adjustment Strength · Max Offset · collision holes
Works in PIE, dead in Sequencer scrub Update Animation in Sequencer · Evaluate Post Process
Mixer missing Sequencer Mixer plugin enabled
Character skates / root fights upper blend Base clips root motion? Upper layer accidentally root-motion travel?
Section titled “10. Related docs”
Doc Role
Animation Mixer in Sequencer (YouTube) Full Mixer UI / layers / blends walkthrough
28-cinematic-benchmark.md · 29 CB product / program order
motion-matching-demo-and-full.md Gameplay MM only — not this cine path
27-mutable-character-weapons.md MetaHuman / appearance (Full)