Vertex Optimization Engine Update

Highlights

• Edge-aware vertex welding: merges near-duplicate vertices while preserving sharp boundaries.
• Degenerate triangle culling: removes zero-area faces that can confuse some slicers.
• Deterministic output ordering: repeated conversions produce stable topology and byte-level reproducible STL streams.

Algorithm details

Edge-aware welding (why it’s safe)

Classic “weld” can destroy sharp corners if it merges across boundaries. Our pass uses edge signals to keep silhouette-critical vertices stable while still merging near-duplicates on flat regions.

• Boundary preservation: vertices near sharp angle changes are protected from cross-edge welding.
• Epsilon-based grouping: near-duplicate vertices are grouped spatially to reduce redundant points.

Degenerate culling

Zero-area (or near-zero) triangles can appear from noisy inputs, contour self-touch, or numerical edge cases. Removing them reduces slicer warnings and prevents weird “missing layer” artifacts.

Deterministic ordering

We sort vertices/faces into a stable order so the same input produces the same STL stream. This makes caching, debugging, and regression testing significantly easier.

12345convert(input) → stl_A
convert(input) → stl_B

# with deterministic ordering:
hash(stl_A) == hash(stl_B)   ✅

What changed in the pipeline

This release adds a post-mesh optimization stage that runs after raster/vector sampling and mesh generation, but before STL serialization.

123456input (PNG/SVG)
  → normalize (colorspace / alpha / viewBox)
  → sample (height field / contours)
  → mesh generation (triangulation)
  → vertex optimization (weld + cull + ordering)   ← NEW
  → STL serialization (stream)

Impact

• Smaller STL files: fewer redundant vertices and faces means faster uploads and faster slicing.
• Cleaner geometry for downstream tools: reduced chance of warnings like “degenerate facets” in slicers.
• No UX changes: the tool UI stays the same; improvements are internal.

What this does NOT do

• It won’t magically smooth a noisy PNG edge — clean the 2D input first.
• It’s not a general-purpose decimator — for polygon strategy, follow Optimize polygon count.
• If your mesh is non-manifold, start with the fix guide: Fix non-manifold STL.