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docs/nodes/Level Grains.md

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+# Level Grains
+
+Shift individual grain regions so they all share a common baseline. Uses the selected reference statistic (mean, median, or minimum) per grain to compute the offset. Useful for consistent grain height comparisons. Equivalent to Gwyddion's level_grains.c module.
+
+## Inputs
+
+| Name | Type | Required | Description |
+|------|------|----------|-------------|
+| field | DATA_FIELD | Yes | Input surface data |
+| mask | IMAGE | Yes | Binary mask defining grain regions |
+
+## Outputs
+
+| Name | Type | Description |
+|------|------|-------------|
+| leveled | DATA_FIELD | Field with grains shifted to a common baseline |
+
+## Controls
+
+| Name | Type | Default | Description |
+|------|------|---------|-------------|
+| reference | dropdown | mean | Per-grain reference: mean, median, or minimum height |
+
+## Notes
+
+- Each connected region in the mask is treated as a separate grain.
+- The target baseline is the average of all per-grain reference values.
+- Use "minimum" reference when grains sit on different substrate heights and you want to align their bases.
+- Combine with Grain Analysis to verify height distributions after leveling.