#weight-paint

red vs blue — blog #2

metahuman builds + the cloth weight-transfer problem

01 — casting the trio in metahuman

roles

blue (student): •Slim, anxious, impulsive, blue jacket.

red (commuter): •Fit, gym clothes, gym bag, good but cornered, family man, rejected from jobs..

woman: Rich, spoiled, distracted with shopping bags and phone, careless with purse

the rabbit hole: clothing weight-transfer

i wanted custom clothes (hoodie, track jacket) to deform nicely on metahumans without deep skinning work. i tried transfer skin weights inside unreal’s skeletal mesh editor.

what i expected

pick target (garment), pick source (metahuman body), hit transfer → done.

what actually happened

decent deformations on single-surface meshes.

chaos on jackets/hoodies with inner + outer shells (double-layered clothing): clipping, flipped normals on bends, exploding verts at elbows.

professor note (key clarification)

the weight transfer in unreal works reliably for single-layer garments. double-layered meshes (inner liner + outer shell) don’t behave well with the built-in transfer. translation: if your jacket has thickness as real geometry, expect problems.

lessons learned

metahuman is fast, but clothes are the bottleneck if you insist on real thickness.

unreal’s transfer weights = great for single-layer garments; double-layers need prep or external binding.

pick your battles: fake thickness with normals beats exploding elbows 9 times out of 10.

what i’ll learn next (plan)

01 — manual weight transfer (clean skinning)

goal: stop relying on auto-transfer for jackets/hoodies and fix elbows/shoulders by hand.

in-engine pass (unreal):

skeletal mesh editor → weight paint mode → smooth/relax around elbow & shoulder loops (2–3 gentle passes).

reassign stray verts: select verts near the joint, reduce influence from the wrong bone (e.g., clavicle) and add to the correct one (upperarm/lowerarm).

pose test: preview at ~90° flex & cross-body reach; iterate until no candy-wrapper twist.

dcc pass (blender/maya), if needed:

copy weights from a body proxy, then hand-paint the garment’s critical loops.

keep garments single-layer where possible; fake thickness with normals.

[image: before/after weight paint at elbow] caption: cleaned shoulder/elbow distribution; no more shearing on 70–90° bends.

02 — chaos cloth (targeted sim, not full garment)

goal: add believable fabric response for a small hero area (e.g., sleeve drag or hem flutter) without simming the entire jacket.

workflow sketch:

select the garment section → create clothing data (chaos).

paint cloth maps:

max weight where you want motion (hems/sleeve).

near-zero weight where it should stay rigid (collar/shoulder seam).

collisions: enable only against the metahuman body (not the whole world), add small collision thickness, toggle self-collision for thicker folds.

set short cache (few hundred frames) and low iterations for previews; bump for final shots.

bake + test with the tackle animation from the storyboard.

[image: chaos paint mask] caption: white = free cloth; dark = pinned/stiff regions. focused sim saves time and avoids explosions.

why this matters for red vs blue

metro is close-quarters → shoulders & sleeves are always in frame. clean weights + a tiny cloth sim sell realism more than extra polygons.

single-layer garments + manual touch-ups beat “auto transfer then pray”.

status

⏸️ paused for the other assignment.

🧠 next up: manual weight paint reps on the hoodie & jacket, then a small chaos cloth pass for a sleeve/hem detail.

🎯 resume plan: finish weight fixes → block chaos sim for shots 5–6 (chase + takedown) → 1080p test render.