Auto Segmentation

Part of the CYM wiki — how to use the automatic segmentation algorithms. For the math and pipeline internals, see Algorithms: Mesh Segmentation.

Where

Import does not auto-segment — region generation is an explicit step, so a large model is browsable the moment it loads:

Seed panel (recommended) — 融合生成 / auto fuse: a planar + multiview + dihedral + eye four-channel vote produces semantic regions in one click (see Seed Tools).
Segments panel — resegment a single existing region with a chosen algorithm and tuned parameters.

The algorithms behind these entries are the same unified backend interface described below.

Algorithms in the panel

The panel exposes 3 of the 8 backend algorithms (auto_segment_v2 IPC, all algorithms available to developers — see the IPC Reference):

Algorithm	Parameters (default)	Good for
Dihedral	angle threshold (30°)	mechanical parts, hard edges — splits where faces meet at steep angles
Curvature K-Means	clusters k (6), normal smoothing iterations (2), use SDF fusion (on), crease threshold (45°)	organic models with smooth patches
Shape Diameter (SDF)	k (0 = auto)	thickness-based separation (limbs, shells)

flowchart LR
    P["Intelligent Segmentation panel"] -->|"select + tune"| A["auto_segment_v2<br/>(algorithm, params)"]
    A --> R["regions replace or join<br/>the current segmentation"]

Behaviour notes

Manual regions survive re-runs — segmentation preserves manually painted regions by default (preserve_manual, can be disabled).
Parameters persist per algorithm — switching algorithms and coming back keeps the sliders where you left them (validated on restore; stored in localStorage via zustand persist).
Progress — long segmentations emit progress events shown in the UI.
Single-region result? If everything merges into one region, your thresholds are too permissive — raise the dihedral angle for hard-surface models or increase k for clustering algorithms.

Region management afterwards

Any segmentation is a starting point: use the Segments panel and canvas tools to merge / split / rename regions, resegment a single region with a different algorithm, or refine with seeds (next page).