Displacement Field
Distort an image using synthetic displacement fields. Supports correlated Gaussian noise and tear-line distortion modes. Equivalent to Gwyddion's displfield.c module.
Inputs
| Name |
Type |
Required |
Description |
| field |
DATA_FIELD |
Yes |
Input field to distort |
Outputs
| Name |
Type |
Description |
| result |
DATA_FIELD |
Distorted field |
Controls
| Name |
Type |
Default |
Description |
| method |
dropdown |
gaussian_1d |
Distortion method: gaussian_1d, gaussian_2d, or tear |
| sigma |
float |
5.0 |
Distortion amplitude in pixels |
| tau |
float |
20.0 |
Lateral correlation length in pixels |
| density |
float |
0.02 |
Tear density — fraction of rows that become tear lines (tear mode only) |
| seed |
int |
42 |
Random seed for reproducibility |
Notes
- gaussian_1d generates a 1D correlated random displacement applied only in the x direction. All rows share the same displacement profile, simulating a systematic lateral distortion.
- gaussian_2d generates independent 2D correlated random displacements in both x and y. This produces a more general warping of the image.
- tear mode simulates scanning artifacts where random horizontal tear lines introduce sudden x-offsets that decay exponentially away from the tear row. This is useful for simulating or studying piezo slip artifacts in SPM data.
- The sigma parameter controls the magnitude of the displacement. Larger values produce more extreme distortion.
- The tau parameter controls the spatial correlation length. A larger tau produces smoother, more slowly varying displacement fields. The ratio sigma/tau roughly determines the local strain.
- For realistic scanning artifacts, use tear mode with low density (0.01--0.05) and moderate sigma.
