Rhino 3D Tip: Rhino CurveBoolean for Fast 2D Region Cleanup

Rhino’s CurveBoolean command is one of the fastest ways to turn overlapping 2D curves into clean, usable closed regions. If you regularly prepare profiles for extrusion, drafting, CNC cutting, or illustration, mastering this tool can save a surprising amount of cleanup time.

Instead of trimming, splitting, and joining curves one piece at a time, CurveBoolean lets you define enclosed areas by simply clicking inside the regions you want to keep. For many workflows, it is the quickest route from sketch geometry to production-ready outlines.

• Use CurveBoolean when curves overlap on the same plane.
  It works best with planar curve layouts such as logos, panel outlines, floor plan regions, part profiles, and cut paths.
• Think of it as a region selection tool.
  After launching the command, Rhino analyzes the intersections and lets you click the areas that should become the final result. This is much faster than manually trimming every segment.
• Start with clean input geometry.
  For best results, make sure your curves are:
  • coplanar
  • properly intersecting
  • free of duplicates
  • not excessively fragmented
• Turn on Osnaps and zoom in before committing.
  Tiny gaps, near misses, or overlapping duplicates can confuse the result. If CurveBoolean does not generate the expected region, check intersections first.
• Use it after importing DWG, AI, or PDF linework.
  Imported 2D files often contain extra segments or stacked curves. CurveBoolean is especially effective after a quick cleanup pass with commands like SelectDup, SelBadObjects, and Join.
• Choose the right output option.
  Depending on the model stage, you may want CurveBoolean to:
  • create new curves
  • delete input objects
  • keep original construction geometry
  Keeping originals is often smarter early in design development.
• Use it to prepare closed profiles for 3D commands.
  Once your regions are resolved, you can immediately move into:
  • ExtrudeCrv for solids or walls
  • PlanarSrf for surface generation
  • Hatch for documentation
  • Offset for material thickness or tool compensation
• Be careful with decorative linework.
  If you have many nested contours or dense pattern curves, isolate only the geometry relevant to the region you need. Too much surrounding linework can make selection harder and results less predictable.
• Combine CurveBoolean with layers for better control.
  Place source curves on a reference layer and output curves on a working layer. This makes edits and downstream selections much easier, especially in fabrication files.
• Use it as a design iteration tool.
  When testing alternate outlines, CurveBoolean helps you quickly evaluate different enclosed shapes without rebuilding the base curves from scratch.

A practical habit is to sketch freely first, then use CurveBoolean as the “cleanup and commit” step before turning 2D ideas into surfaces, solids, or documentation. It is a small command with a major productivity payoff.

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