Seed Tools

Part of the CYM wiki — seed-based segmentation: place seeds, grow regions, fuse results. Internals: Algorithms: Seed Grow & Fuse.

Seeds → fuse → export, end to end:

The Seed panel gives fine-grained control on figure-type models where generic auto segmentation needs help. It has two modes:

• Auto (fuse) — recommend seeds automatically, grow, then fuse with tiny-region cleanup
• Manual (grow) — you place the seeds, the region grows from them

flowchart TD
    R["Recommend seeds<br/>(or detect planar / multiview / cross-section / eyes)"] --> P["place / adjust seed points"]
    P --> G["grow<br/>(barrier angle + optimizer)"]
    G --> F["fuse + tiny-region merge"]
    F --> REG["final regions"]
    EYE["Eye detection"] -. eye regions are protected .-> REG

Seed recommendation

• Recommended seeds — saliency-based suggestions with sliders for count, curvature weight and concavity weight.
• Planar regions — flat-area detection (angle threshold, distance factor, minimum faces).
• Multiview — regions consistently seen from multiple views (view count, angle threshold, minimum faces, match threshold).
• Cross-section — features found on slicing planes per axis.
• Detect eyes — one click, global scan (no ROI needed); a ROI-mode also exists for developers (see IPC Reference).

Suggestions are cleared automatically before a new eye detection so stale suggestions can't pollute results.

Growing regions

Each seed grows into a region bounded by the barrier angle — adjacent faces whose normals differ more than the barrier stop the growth. Toggle the optimizer to post-process the grown regions. Add or move seeds and grow again; regions you keep are preserved.

Fusing

Fuse merges over-seeded fragments, with aggressive tiny-region merging (micro-regions are absorbed and a live size breakdown is shown in the status area) and a reverse-split guard against runaway merges. Eye regions detected earlier are protected — they survive internal cuts and merges.

The fold-angle threshold

The Dihedral ° slider (0–35°, default 5° since v0.1.1) controls where the partition is allowed to cut. Lower = finer, higher = coarser:

Pressing Fuse & generate runs a staged pipeline with a live progress bar: planar detection → multi-view evidence → fold-angle backbone → edge vote.

Adjacent regions never share a colour

The viewport colours each region by its label. The fuse allocates labels so that touching regions always land on different palette slots (greedy graph colouring over the region adjacency, 30-slot palette) — two neighbouring regions can safely look at each other without reading as one blob.

Lasso regions

For the areas where geometry has no boundary to offer (a smooth cheek, a flat wall band), draw a region by hand with the Lasso tool: click points around the area, then click near the start point (or press Enter) to close.

Closing the loop shows the same progress bar — snap → boundary completion → region capture → smoothing → commit — because on million-face meshes every one of those stages is real work. The boundary between clicked points follows the mesh surface (A* shortest path), so the outline hugs the geometry instead of cutting through it.

When to use what

Real runs of every case above live in the Examples Gallery.