What is ʼBoundary Detectionʼ in BricsCAD?

Short Answer

Boundary Detection in BricsCAD is the process of finding a closed area from existing geometry so you can create a polyline or hatch boundary automatically. The most common professional method is the BOUNDARY command using an internal pick point. It only works reliably when the enclosing geometry is fully closed.

What You Need to Know Before

Warning: Boundary Detection often fails because of tiny gaps, overlapping endpoints, or objects that only look closed at your current zoom level. If layers are locked or the area touches complex hatch/island geometry, BricsCAD may detect the wrong region or none at all.

How to Create a Boundary

• Command: BOUNDARY

• Shortcut: BO

• Quick Steps:

  1. On the Ribbon, open the Draw panel and start Boundary; alternatively type BOUNDARY or BO.
  2. In the Boundary Creation dialog, set Object type to Polyline and use Pick Points as the standard method.
  3. Click inside the enclosed area, review options like Island detection, then press Enter to create the boundary.

Variables & Settings

• Key Setting: Island detection

• Expert Setting: This option controls whether enclosed inner areas are ignored, included, or treated as separate islands. For rooms, columns, and donut-shaped regions, the wrong island mode can generate an incorrect boundary loop.

Why it Fails

• Cause 1 (Geometry): Small gaps, non-touching endpoints, or crossing objects prevent BricsCAD from finding a closed loop.
• Cause 2 (Layers/Locks): Boundary source objects on locked or problematic reference layers can interfere with selection or produce incomplete results.
• Cause 3 (Command/Logic): Picking near multiple adjacent spaces or inside areas with nested islands can make the command detect the wrong region.

Quick Fix & Best Practice

• Quick Fix: Run PEDIT with Join, or use FILLET with radius 0 to close small endpoint gaps before running BOUNDARY again.
• Manager’s Verdict: Use Boundary Detection for fast room outlines, hatch limits, and cleanup work, but avoid relying on it for production geometry until you verify closure and island behavior.

FAQ

Is Boundary Detection the same as Hatch?
No, hatch can use boundary detection, but BOUNDARY creates actual boundary objects.

Can Boundary create a polyline in BricsCAD?
Yes, set the object type to Polyline in the Boundary options.

Why does BOUNDARY pick the wrong area?
Usually because of open gaps, nearby enclosed regions, or incorrect island detection settings.

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