Terrace Fit
Segment a surface into flat terraces separated by atomic steps, fit a polynomial to each terrace, and extract step heights. Set n_terraces=0 for automatic detection via histogram clustering. Equivalent to Gwyddion's terracefit.c module.
Inputs
| Name |
Type |
Required |
Description |
| field |
DATA_FIELD |
Yes |
Input surface with step/terrace features |
Outputs
| Name |
Type |
Description |
| result |
DATA_FIELD |
Residual, fitted surface, or label map |
| step_heights |
RECORD_TABLE |
Per-terrace heights and step height differences |
Controls
| Name |
Type |
Default |
Description |
| n_terraces |
INT |
0 |
Number of terraces to fit; 0 = auto-detect from histogram peaks (0–50) |
| broadening |
FLOAT |
1.0 |
Smoothing factor for terrace detection; larger values merge noisy pixels (0.1–20.0) |
| poly_degree |
INT |
0 |
Polynomial degree per terrace: 0 = constant (flat), 1 = linear, 2 = quadratic, 3 = cubic (0–3) |
| output |
dropdown |
residual |
Output mode: residual (original minus fit), fitted (fit surface), or labels (terrace assignment map) |
Notes
- Use poly_degree=0 for ideal crystalline surfaces with perfectly flat terraces. Higher degrees compensate for sample curvature within each terrace.
- Auto-detection works best when terraces are well-separated in height. For noisy surfaces, increase broadening to improve terrace segmentation.
- The labels output assigns integer IDs (0, 1, 2, ...) to each terrace, ordered by height.
