31 lines
1.5 KiB
Markdown
31 lines
1.5 KiB
Markdown
# Shade
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Render a DATA_FIELD as a directional hillshade image using Lambertian reflectance. Surface normals are estimated from Sobel gradients, and shading intensity is computed from the dot product with a configurable light direction. Equivalent to Gwyddion's `shade.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 field to shade |
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## Outputs
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| Name | Type | Description |
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|------|------|-------------|
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| shaded | DATA_FIELD | Shaded surface rendering |
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## Controls
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| Name | Type | Default | Description |
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|------|------|---------|-------------|
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| azimuth | FLOAT | 0.0 | Light direction in degrees: 0 = north, 90 = east, 180 = south, 270 = west (0-360) |
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| elevation | FLOAT | 45.0 | Light elevation angle above the horizon in degrees (0-90) |
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| blend | FLOAT | 0.5 | Blend factor between original data and shading: 0.0 = original data only, 1.0 = shading only (0.0-1.0) |
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## Notes
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- Surface normals are computed using Sobel gradient operators, providing good noise resilience compared to simple finite differences.
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- An azimuth of 315° (northwest illumination) is a common choice that produces natural-looking topographic shading.
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- Elevation of 90° gives flat, uniform lighting; lower angles emphasize surface texture and fine features.
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- The blend parameter controls how much shading modulates the original height data. Use 0.5 for a balanced view, or 1.0 for pure shaded relief.
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