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