fn sample_warp_displacement(field: &WarpField<'_>, x: f32, y: f32) -> (f32, f32)Expand description
Look up the warp displacement at preset-space position (x, y)
from field. Bilinear-interpolates across the four nearest mesh
cells so the segment direction stays smooth across the grid
boundaries. Returns (dx, dy) in preset-space UV units
(uv_warp - uv_orig).