82 lines
2.5 KiB
Python
82 lines
2.5 KiB
Python
"""Facet analysis — orientation distribution of surface facets."""
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from __future__ import annotations
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import numpy as np
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from backend.node_registry import register_node
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from backend.data_types import DataField
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@register_node(display_name="Facet Analysis")
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class FacetAnalysis:
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@classmethod
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def INPUT_TYPES(cls):
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return {
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"required": {
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"field": ("DATA_FIELD",),
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"n_bins": ("INT", {"default": 180, "min": 30, "max": 720}),
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"kernel_size": ("INT", {"default": 3, "min": 3, "max": 9, "step": 2}),
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}
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}
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OUTPUTS = (
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('DATA_FIELD', 'facet_map'),
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)
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FUNCTION = "process"
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DESCRIPTION = (
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"Compute the facet orientation distribution of a surface. "
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"Outputs a 2D histogram (stereographic projection) where the x-axis "
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"is the azimuthal angle (phi) and y-axis is the inclination (theta). "
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"Intensity represents how much surface area faces each orientation. "
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)
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KEYWORDS = ("orientation", "stereographic", "azimuth", "inclination", "slope", "crystal")
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def process(self, field: DataField, n_bins: int, kernel_size: int) -> tuple:
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data = np.asarray(field.data, dtype=np.float64)
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# Compute gradients with Sobel-like kernel for robustness
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from scipy.ndimage import sobel
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gx = sobel(data, axis=1) / (kernel_size * field.dx)
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gy = sobel(data, axis=0) / (kernel_size * field.dy)
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# Convert to spherical angles
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theta = np.arctan(np.sqrt(gx**2 + gy**2)) # inclination from vertical
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phi = np.arctan2(gy, gx) # azimuthal angle
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# Map to [0, pi/2] and [0, 2*pi]
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theta_flat = theta.ravel()
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phi_flat = (phi.ravel() + 2 * np.pi) % (2 * np.pi)
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# Build 2D histogram (stereographic projection)
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theta_max = float(theta_flat.max()) if theta_flat.size > 0 else np.pi / 4
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theta_max = max(theta_max, 0.01)
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n_theta = max(1, n_bins // 4)
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n_phi = n_bins
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hist, _, _ = np.histogram2d(
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theta_flat,
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phi_flat,
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bins=[n_theta, n_phi],
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range=[[0.0, theta_max], [0.0, 2 * np.pi]],
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)
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# Normalise so it represents a probability density
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total = hist.sum()
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if total > 0:
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hist = hist / total
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facet_field = DataField(
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data=hist,
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xreal=360.0,
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yreal=np.degrees(theta_max),
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si_unit_xy="deg",
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si_unit_z="",
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domain="spatial",
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)
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return (facet_field,)
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