Bugfix: surface interpolation with unequal number of control points

[Roxana-P]

Overview

Description
As pointed out in issue #99, the current routine splinepy.BSpline.interpolate_surface does not allow an unequal number of sampling points. This is due to a wrong ordering of the sampling points in l.85.
This code fixes this issue and transposes the control points, as they are otherwise incorrectly ordered. I am happy on feedback to improve the efficiency of l.108-114.

Addressed issues

• Issues addressed: Bug in interpolate surface #99

Showcase

The example illustrated in #99.

import numpy as np
import splinepy


def interpolate_function(f, samples_per_direction):
    """Interpolate the function f with a given number of samples 
    in each direction on the interval [-1, 1] x [-1, 1]

    Parameters
    ----------
    f : function
        Function to interpolate
    samples_per_direction : list
        Number of samples per direction

    Returns
    -------
    np.ndarray, splinepy.BSpline
        Target points and interpolating BSpline
    """

    # Create dataset
    x = [np.linspace(-1, 1, samples_per_direction[0]), 
        np.linspace(-1, 1, samples_per_direction[1])]
    xx, yy = np.meshgrid(x[0], x[1])

    target_points = np.vstack(
        (xx.flatten(), yy.flatten(), h(xx, yy).flatten())
    ).T

    interpolated_surface = splinepy.BSpline.interpolate_surface(
        target_points,
        size_u=samples_per_direction[0],
        size_v=samples_per_direction[1],
        degree_u=2,
        degree_v=2,
    )
    return target_points, interpolated_surface
    
def h(x, y):
    return x + y

if __name__ == "__main__":
    try:
        import gustaf as gus

        gustaf_available = True
    except ImportError:
        gustaf_available = False


    for sample_sizes in [[3, 3], [3, 4], [4, 3], [20, 20], [25, 20]]:
        target_points, interpolated_surface = interpolate_function(h, sample_sizes)
        
        if gustaf_available:
            bspline = gus.BSpline(**interpolated_surface.todict())
            gus.show.show_vedo([bspline])

Results:
Number of control points (3,3)

Number of control points (3,4)

Number of control points (4,3)

Number of control points (20, 20)

Number of control points (5, 20)

Checklists

• Documentations are up-to-date.
• Added example(s)
• Added test(s)

[j042]

Awesome, thank you! This has been bugging me for a long time. I will remove reorganize param in next pr