形状凸起的船体面积给出的结果与scipy.ConvexHull区域完全不同？

Question

我肯定遗漏了一些非常明显的东西，但scipy.ConvexHull.area计算的面积与shapely.convex_hull.area相比似乎有很大的不同。我得到了

Scipy Convex Hull Area: 457761.9061526276, Shapely Convex Hull Area: 13192154623.86528

from shapely.geometry import MultiPoint
from scipy.spatial import ConvexHull
import json


def convex_hull_compare():
    with open("./test_points.json", 'r') as f:
        points = json.load(f)
        print(points)
        hull = ConvexHull(points)
        ch_area = MultiPoint(points).convex_hull.area

        print(
            f"Scipy Convex Hull Area: {hull.area}, Shapely Convex Hull Area: {ch_area}")
        # Scipy Convex Hull Area: 457761.9061526276, Shapely Convex Hull Area: 13192154623.86528


if __name__ == "__main__":
    convex_hull_compare()

我已经将test_points.json上传到了Gist 这里上，并编写了代码的最小版本，以便于复制。

Answer 1

一个有用的注释链接了以下问题：它的要点是对于2D点，我们需要的是ConvexHull.volume，而不是ConvexHull.area。

这确实给了我们正确的答案，但这确实令人困惑，因为文档中根本没有提到这一点。

from shapely.geometry import MultiPoint
from scipy.spatial import ConvexHull
import json


def convex_hull_compare():
    with open("./test_points.json", 'r') as f:
        points = json.load(f)
        print(points)
        hull = ConvexHull(points)
        ch_area = MultiPoint(points).convex_hull.area

        print(
            f"Scipy Convex Hull Area: {hull.area}, Shapely Convex Hull Area: {ch_area}")
        # Scipy Convex Hull Area: 457761.9061526276, Shapely Convex Hull Area: 13192154623.86528

        print(
            f"Scipy Convex Hull Area: {hull.volume}, Shapely Convex Hull Area: {ch_area}")
        #Scipy Convex Hull Area: 13192154623.865295, Shapely Convex Hull Area: 13192154623.86528


if __name__ == "__main__":
    convex_hull_compare()