Facet Analysis
Compute the facet orientation distribution of a surface. Outputs a 2D histogram (stereographic projection) where the x-axis is the azimuthal angle and y-axis is the inclination. Equivalent to Gwyddion's facet_analysis.c module.
Inputs
| Name |
Type |
Required |
Description |
| field |
DATA_FIELD |
Yes |
Input surface |
Outputs
| Name |
Type |
Description |
| facet_map |
DATA_FIELD |
2D histogram of facet orientations (phi vs theta) |
Controls
| Name |
Type |
Default |
Description |
| n_bins |
INT |
180 |
Number of azimuthal bins; theta bins = n_bins/4 (30–720) |
| kernel_size |
INT |
3 |
Sobel gradient kernel size in pixels (3–9, odd) |
Notes
- The output is a normalised probability density — it sums to 1.0.
- X-axis: azimuthal angle phi (0–360°). Y-axis: inclination theta (0° = flat, max = steepest facet).
- A flat surface produces a single bright spot near theta=0. A surface with distinct facets shows multiple peaks.
- Larger kernel_size smooths the gradient estimate, reducing noise sensitivity.
