ZBrush Tip: Lock Real‑World Scale in ZBrush Before Export

Always verify real‑world scale before exporting from ZBrush to external renderers—small mismatches ripple into lighting, materials, displacement, dynamics, and even camera behavior.

Why scale matters across DCC/renderers:

• Lighting and exposure: physically based lights expect real units (lumens/candela). Wrong scale skews intensity and falloff.
• Shading and SSS: skin or wax subsurface radii are in mm/cm. Incorrect scale breaks lookdev.
• Displacement and normal maps: intensity and filter widths rely on scene units; mismatched scale yields faceting or bloating.
• Camera DOF and motion blur: aperture and focal distances behave unpredictably if your model is microscale or gigantic.
• Simulation/dynamics: cloth, hair, and rigid bodies need real sizes and masses to be stable.

Practical ZBrush workflow to lock scale:

1. Decide target units up front based on your destination:
   • Maya/Arnold: centimeters
   • Cinema 4D/Redshift: centimeters
   • Blender/Cycles: meters (Metric)
   • 3ds Max/V‑Ray: set System Unit to centimeters (recommended)
2. Measure your asset in ZBrush:
   • Use the Gizmo 3D/Transpose line or Ruler to read a known dimension (e.g., character height = 180 cm).
   • Check Tool > Geometry > Size > XYZ Size to view the current bounding dimension.
3. Normalize without losing intent:
   • Avoid Deformation > Unify after you’ve established real scale—it resets to ZBrush’s preferred internal size.
   • If you must normalize early, do it before detailing and then set a precise real‑world size immediately after.
4. Set exact real‑world size:
   • Use ZPlugin > Scale Master to define the largest dimension numerically (e.g., Set Size = 180 cm for a character).
   • Apply to all SubTools via Scale Master so the entire stack remains consistent.
5. Lock export behavior:
   • In Tool > Export, leave Scale at 1 and Offsets at 0 once your scene scale is correct.
   • For FBX (ZPlugin > FBX ExportImport), keep Scale = 1.0 unless your DCC requires a known factor.
6. Validate in the destination DCC:
   • Confirm the bounding size equals your target (use a unit cube or a 1 m/100 cm ruler in the DCC).
   • Test a real‑world light (e.g., 1000 lm point light) and SSS radius to see if results look plausible.

Map‑related considerations:

• Displacement: generate 32‑bit EXR; keep Scale/Mid consistent. In the renderer, use real‑world height values (mm/cm) rather than arbitrary intensity.
• Normal maps: unaffected by absolute scale for shading, but filtering and mip bias benefit from correct UV density at real size.
• Thickness: if you model shells (clothing, armor), set intended millimeter thickness before baking—SSS and collision depend on it.

Quick checklist before you hit render:

• XYZ Size matches the brief (cm or m as required).
• Tool > Export Scale = 1; no unexpected Offsets.
• FBX/OBJ import into DCC measures correctly with a unit ruler.
• Test light, DOF, and SSS produce physically reasonable results.

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