DCC Scene Origin Scale and Units Checklist

1. Declare the measurement contract

Write the master Units convention for modeling, export, and destination import: for example centimeters in the engine and meters in interchange metadata. Record whether one grid division has semantic meaning. Do not infer size from appearance. Include expected real dimensions, up axis, forward axis, handedness, and tolerance. A door, character, vehicle, and calibration cube make useful anchors because their wrong size is easier to detect than a generic prop.

2. Place the origin for behavior

Choose Origin placement from use: a standing character at the ground between feet, a hinged door on the hinge line, a wheel at its axle, a modular wall on a snap corner, and a projectile near its center of mass. Keep world origin decisions separate from object pivot convenience. For large worlds, define rebasing or floating-origin policy. Capture the chosen point with a viewport overlay and numeric transform rather than a screenshot alone.

3. Resolve scale without damaging data

Inspect object, parent, armature, and geometry-level Scale. Apply or freeze transforms only when downstream consequences are understood: modifiers, constraints, children, animation curves, skin bind matrices, and procedural nodes can change. Prefer fixing a duplicate and comparing it to the approved source. Avoid negative scale on shipping objects unless the target pipeline explicitly supports mirrored tangents, winding, collision, and determinant handling.

4. Keep hierarchy transforms predictable

Check parent inverse matrices, inherited scale modes, constraints, and hidden transform nodes. Non-uniform parent Scale can shear children, alter normals, and destabilize rigging. For modular assets, keep root transforms identity at handoff and move placement into the destination scene. If offsets are required, put them in a documented export root rather than silently baking them into mesh vertices or animation channels.

5. Validate export and import conversion

Export a calibration cube alongside the asset, then inspect interchange metadata and importer settings. Disable automatic unit conversion only when the pipeline has another verified conversion. Compare source bounding dimensions to imported dimensions numerically. Test one round trip; repeated export and import should not multiply Scale by 100 or 0.01. Record preset version because a colleague’s local preset can override otherwise correct scene Units.

6. Check dependent systems at true size

Run collision, gravity, cloth, particle, depth-of-field, camera clipping, light attenuation, displacement, and texture-density checks at intended dimensions. A model may look correct next to nothing while producing excessive simulation speed or precision jitter. Skeleton retargeting also assumes comparable proportions and root motion scale. Use a ruler overlay and a representative gameplay camera, not only an orthographic modeling view.

7. Work a modular-kit correction

A wall kit modeled in meters imports one hundred times too small because the FBX exporter and engine importer both convert Units. Keep source dimensions in meters, set one explicit export conversion, and restore importer scale to 1. Move each module Origin to the lower-left snap corner and apply positive object Scale after checking modifiers. A one-meter cube and two snapped wall pieces then prove dimensions, pivot behavior, seam continuity, and collision alignment.

8. Recognize transform failure signatures

Wrong gravity or camera clipping indicates global size error. Parts drift during animation when armature and mesh scales disagree. Dark mirrored shading points to negative determinant or tangent reversal. Snapping leaves gaps when origins use inconsistent corners. Large-coordinate jitter signals insufficient world-origin strategy. An importer showing 100 or 0.01 often reveals duplicate conversion. Fix the earliest contractual mismatch instead of compensating each downstream system separately.

9. Archive evidence and acceptance values

Deliver scene-unit settings, object and hierarchy transforms, bounding dimensions, origin coordinates, axis convention, exporter and importer presets, calibration object, and destination screenshots. State tolerances for dimension, pivot location, and round-trip conversion. Include collision and animation tests when applicable. Approval means identity shipping transforms where required, positive determinant, expected dimensions, stable snap behavior, and no undocumented conversion hidden in a workstation preset.

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