Frequency Split
Separate a DATA_FIELD into low-frequency and high-frequency components using an FFT-based Gaussian filter. The low-pass output contains smooth, large-scale variations while the high-pass output contains fine detail and noise. Equivalent to Gwyddion's freq_split.c module.
Inputs
| Name |
Type |
Required |
Description |
| field |
DATA_FIELD |
Yes |
Input field to split |
Outputs
| Name |
Type |
Description |
| low_pass |
DATA_FIELD |
Low-frequency (smoothed) component |
| high_pass |
DATA_FIELD |
High-frequency (detail) component |
Controls
| Name |
Type |
Default |
Description |
| cutoff |
FLOAT |
0.1 |
Cutoff frequency as a fraction of Nyquist (0.001–0.5) |
Notes
- The cutoff is relative to the Nyquist frequency. A value of 0.5 effectively passes everything (no filtering), while 0.001 aggressively removes nearly all spatial frequencies from the low-pass output.
- The two outputs always sum to the original field: low_pass + high_pass = input.
- Useful for separating roughness from waviness, or for removing long-range background while preserving features.
- The filter operates in the frequency domain via FFT, so it handles periodic boundaries naturally.
