Flatten Base
Level the flat base of a surface that has raised features (particles, grains). Uses a height percentile threshold to identify base pixels, fits a polynomial to those pixels, and subtracts it. Unlike plane level, this ignores tall features that would bias the fit. Equivalent to Gwyddion's flatten_base.c module.
Inputs
| Name |
Type |
Required |
Description |
| field |
DATA_FIELD |
Yes |
Input field with raised features on a tilted base |
Outputs
| Name |
Type |
Description |
| leveled |
DATA_FIELD |
Field with base leveled |
Controls
| Name |
Type |
Default |
Description |
| threshold_percentile |
FLOAT |
30.0 |
Height percentile below which pixels are considered base (5–80) |
| poly_degree |
INT |
2 |
Polynomial degree for base fit: 0 = constant, 1 = plane, 2 = quadratic (0–5) |
Notes
- Set the threshold percentile so that it includes most of the base but excludes the features. For sparse particles on a flat substrate, 20–40% typically works well.
- poly_degree=1 is equivalent to plane leveling on the base only. Use 2–3 for curved substrates.
- If the features dominate the surface (>50% coverage), this node may not give good results — consider Median Background instead.
