Tutorial — Sculpting Expression Targets for the Expression Editor

Augmented Traveler local tutorial. Back to ZBrush — Tutorials · prerequisites: Tutorial — ZBrush No-Topology-Change Round Trip and Tutorial — Expression Editor Fundamentals

How to fix one expression on a figure's calibrated face by sculpting it in ZBrush and returning it to the Expression Editor. Use this after the neutral is final and an MH1 calibration shows an expression that looks wrong.

Draft. Written from Epic's Expression Poses documentation and our round-trip rules. Validate after the first MH1 calibration and correct button names here.

1. When to sculpt an expression, and when not

Sculpt one when:

Don't sculpt one:

Where to start: the MH12 set is a useful shortlist of the expressions that matter most for likeness:

2. How expressions are stored

3. Get the posed head out of Maya

  1. In the Expression Editor, switch to Expression Poses. In the graph, select the target expression (for example the Lip Corner Puller primary). Use Preview Selected Node to see it by itself.
  2. Check its downstream nodes (Select Downstream Nodes) so you know which combinations the change will affect.
  3. With the expression applied, duplicate the LOD0 head in its posed state and delete its history. Export it as OBJ with the same settings as the neutral round trip.
  4. Also export the neutral LOD0 for reference, so ZBrush has both.

4. Sculpt in ZBrush

  1. Import the posed head as a new tool. Check that its vertex count matches the neutral.
  2. Store a morph target of the posed state.
  3. Subdivide with Smt on and make a layer named expr_<name>.
  4. Sculpt the correction. Follow the round-trip rules: move points, never add or remove them, and don't slide landmarks. Typical fixes:
    • Smile: stretch the cheek mass upward; fold the nasolabial crease at the figure's age; keep the lip line on the lip vertices; pull the lips clear of the teeth.
    • Blink / Squint Inner: keep the lid edges on the eyeball's curve; fold the upper-lid skin rather than letting it pass through.
    • Brows Raiser: forehead folds only as a broad shape; fine wrinkles belong in the animated maps.
  5. Check it against the neutral: toggle the morph target to compare. Fix only the parts that are wrong.
  6. Mirror only if the expression should be symmetrical.
  7. Go to level 1 and export as OBJ: AT_<Figure>_expr_<name>_v###.obj. Check the vertex count again.

5. Bring it back into the expression

  1. Import the OBJ into Maya and run the blendShape vertex-order test from the round-trip tutorial.
  2. In Expression Poses, with the target expression active, select the head mesh and then the sculpt, and click Transfer Vertex Positions.
  3. Click Update to commit the change to that expression.
  4. Run Joint Matching (machine-learning joint matching in the utility toolbar) so joints carry as much of the change as possible.
  5. Use Frame Analysis and Preview Selected Node to check the expression by itself and in its downstream combinations.
  6. Update the DNA, save and reload. Test the expression in a short animated sequence, not only as a still.

6. Check before moving on

Sources