ZBrush Tip: Edge-Preserving Smoothing with Polygroups and Smooth Groups

Control where your model smooths by leveraging Smooth Groups to preserve crisp edges while refining surfaces.

Core idea

• Define boundaries with Polygroups.
• Use Smooth brush settings that respect those boundaries.
• Complement with creasing and polish operations for production-safe results.

Set up clean group boundaries

• Create Polygroups from angles: Tool > Polygroup > Group by Normals (try Angle 35–45º). This quickly marks hard edges as separate groups.
• For complex assets, try Auto Groups or PolygroupIt to segment by islands/curvature.
• Toggle PolyFrame (Shift+F) to visualize edges you want preserved during smoothing.

Brush-based smoothing that respects groups

• Hold Shift (Smooth), then open Brush > Smooth Brush Modifiers:
  • Weighted Smooth Mode: 5–6 for relax-type smoothing that preserves volume.
  • Smooth Groups: set to 1–2 to constrain smoothing within each Polygroup, preventing bleed across edges.
• Optional: Brush > Auto Masking > Mask By Polygroup = 100 to further protect other groups during regular sculpting (not just smoothing).
• Alternate smooth trick: start a Smooth stroke (hold Shift), then release Shift while still stroking to switch to your Alternate Smooth behavior. Assign a groups-aware Smooth variant to Alt for quick edge-safe refinement.

Global operations for hard-surface confidence

• Tool > Deformation > Polish by Groups: tightens surfaces while preserving group borders. Use low iterations first; increase as needed.
• Dynamic smoothing without losing edges:
  • Tool > Geometry > Crease > Crease PG to crease Polygroup borders.
  • Enable Dynamic Subdiv; adjust Smooth Subdiv to preview final smoothness while creases keep edges sharp.
  • Tune Crease Level to let edges gradually soften after a few subdivisions, if desired.
• ZRemesher with groups: enable KeepGroups and adjust SmoothGroups to control how much group borders are softened during remesh (low values keep borders crisp, higher values gently bevel them).

Workflow tips

• Use smaller Smooth brush size and lower ZIntensity near edges to avoid unintended rounding.
• Combine HPolish or Trim brushes inside groups for planar refinement without crossing borders.
• Before heavy topology changes, Store Morph Target to quickly restore edge integrity with the Morph brush if anything drifts.
• If smoothing “tears” thin shells, enable Brush > Auto Masking > BackfaceMask to protect opposite surfaces.

When to use it

• Hard-surface panels, armor seams, and mechanical cutlines that must remain tight while you smooth large surfaces.
• Cloth seams or organic transitions where you want controlled blending across defined boundaries.

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