ZBrush Tip: Manage Backfaces and Inverted Normals with ZBrush Display Properties

Quick control over backfaces and inverted normals can save hours—here’s how to use Display Properties effectively.

When polygons appear to “disappear” as you rotate the model, you’re seeing one‑sided faces. ZBrush renders polygons from their normal direction only, which is ideal for performance but tricky with thin surfaces, booleans, or imported meshes. Tool > Display Properties gives you two essential switches: Double and Flip.

• Double: Displays both sides of polygons without changing the mesh. Great for sculpting thin shells (cloth, leaves, hair cards) or evaluating booleans. Turn it off when checking for true normal direction before export.
• Flip: Reverses the polygon normals. Use this when a subtool is truly inside‑out (faces vanish with Double off). Flip is a geometry change and will affect exports.

Recommended workflow:

• Select the affected SubTool.
• Go to Tool > Display Properties.
• Toggle Double on to verify whether the issue is just viewport culling. If your surface now appears, normals are likely fine but you need backface visibility while working.
• If faces still behave incorrectly with Double off, click Flip to correct the normals. Toggle Double back off and rotate the model to confirm.
• Enable Brush > Auto Masking > BackfaceMask when sculpting thin areas with Double on to prevent strokes from affecting the opposite side.

Situations where Double and Flip shine:

• After Live Boolean: The resulting mesh may have mixed normal directions—Flip the compiled result if sections vanish.
• Imported assets: OBJ/FBX from DCCs can carry inverted normals; verify with Double and commit with Flip if needed.
• Clothing and accessories: Keep Double on for convenience during sculpting, but turn it off before baking maps or exporting to spot any unintended flips.

Best practices and pitfalls:

• Use Double as a working aid only; it can hide real normal problems. Always run a “Double off” pass before baking or export.
• Combine Double with BackfaceMask to avoid polypaint and sculpt bleed‑through.
• For performance, leave Double off on heavy scenes unless needed.
• Assign a custom hotkey: Ctrl+Alt+click Double or Flip, press your key, then Store Config (Preferences) to keep it.
• Before export (Tool > Export or via FBX ExportImport), verify normals with Double toggled off to ensure downstream apps render correctly.

Pipeline tip: Engines and renderers can use double‑sided materials, but it’s still best practice to keep normals consistently outward and use Double only for viewport convenience. This avoids lighting artifacts and ensures clean baking.

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