---
name: Silhouette cookie cutter approach
description: The cumulative model silhouette is used to split every layer into boundary vs interior
type: project
---

The correct way to separate boundary (cutout ring) from interior (model cavities) in each layer:

1. `cumulativeCross` = union of all cross-sections across all depths = the model's full silhouette from the cutting direction
2. For each layer's pocket geometry:
   - Boundary = pocket MINUS silhouette (material outside the model outline)
   - Interior = pocket INTERSECT silhouette (cavities within the model outline)
3. This silhouette is constant across all layers — it's the "cookie cutter"

**Why:** Previously used per-layer model outline which changed shape at every depth and failed for solid shapes without holes. The silhouette approach works universally.

**How to apply:** If boundary/interior separation needs changes, the silhouette (cumulativeCross) is the dividing line. Filter boolean sliver artifacts with area < 0.01mm².