Generates a height-based scalar field from a boundary field.
For each position, samples the boundary to obtain its height and returns the difference between the position's z coordinate and that height.
Positive values indicate positions above the boundary, while negative values indicate positions below it.
Generates a height-based scalar field from a boundary field.
For each position, samples the boundary to obtain its height and returns the difference between the position's z coordinate and that height.
Positive values indicate positions above the boundary, while negative values indicate positions below it.