# Wrap a Point Cloud in a Convex Hull
# ===================================

# Create a convex hull from a point cloud using tetrahedralization and surface
# extraction.
import numpy as np
import pyvista as pv
from pyvista import examples

# Load a point cloud
# ==================

# The `download_horse_points()` dataset is a
# dense scan of a horse statue. Subsample it to keep the hull geometry light.
full_cloud = examples.download_horse_points()
rng = np.random.default_rng(seed=2)
sample_ids = rng.choice(full_cloud.n_points, size=4000, replace=False)
cloud = pv.PolyData(full_cloud.points[sample_ids])
cloud

# Extract the outer hull
# ======================

# A Delaunay tetrahedralization followed by surface extraction returns the
# outer surface of the cloud.
hull = cloud.delaunay_3d(alpha=cloud.length).extract_surface(algorithm=None)

pl = pv.Plotter()
pl.add_points(
    cloud,
    color='black',
    point_size=6,
    render_points_as_spheres=True,
)
pl.add_mesh(hull, color='royalblue', opacity=0.4, show_edges=True)
pl.camera_position = pv.CameraPosition(
    position=(0.4, -0.5, 0.25),
    focal_point=cloud.center,
    viewup=(0, 0, 1),
)
pl.show()

# Inspect the wrapped surface
# ===========================

# The result is a closed surface enclosing every input point.
hull

# ----------------------------------------------------------------------
# Generated by sphinx-examples-as-code https://github.com/pyvista/sphinx-examples-as-code