get_sdf_pts() returns wrong SDF for single-point queries (PCU method)

[gattia]

Description

Mesh.get_sdf_pts() using the default PCU method returns incorrect signed distance values when called with a single query point (shape (1, 3)). With 2+ points, results are correct.

Reproduction

import numpy as np
import pyvista as pv
from pymskt.mesh import Mesh

cyl = pv.Cylinder(center=[0,0,0], direction=(0,0,1), radius=5.0, height=20.0, resolution=50)
mesh = Mesh(cyl.triangulate())

Single point on the surface — WRONG

pts_1 = np.array([[5.0, 0.0, 0.0]])
sdf_1 = mesh.get_sdf_pts(pts_1)
print(f"1 point (surface): {sdf_1}") # Returns -11.84 (should be ~0)

Same point with a second point — CORRECT

pts_2 = np.array([[5.0, 0.0, 0.0], [0.0, 0.0, 0.0]])
sdf_2 = mesh.get_sdf_pts(pts_2)
print(f"2 points: {sdf_2}") # Returns [0.01, -4.99] (correct)
Output

1 point (surface): -11.84160892722138
2 points: [ 0.00986164 -4.98872184]
Expected behavior
The SDF for a point on the cylinder surface should be ~0 regardless of whether it is queried alone or with other points.

Environment
Python 3.9.19
PCU (point_cloud_utils) as the SDF backend
Tested on Linux

[gattia]

Fixed in PR #48 (merged to main). The workaround duplicates the single query point so PCU sees n >= 2, then returns only the first result. Test added in testing/mesh/meshTools/pcu_sdf_single_point_test.py. Available in v0.1.20.