"""
.. _voxelize_surface_mesh_example:

Voxelize a Surface Mesh
~~~~~~~~~~~~~~~~~~~~~~~

Create a voxel model (like legos) of a closed surface or volumetric mesh.

This example also demonstrates how to compute an implicit distance from a
bounding :class:`pyvista.PolyData` surface.

"""

import numpy as np

import pyvista as pv

# sphinx_gallery_thumbnail_number = 2
from pyvista import examples

# Load a surface to voxelize
surface = examples.download_foot_bones()
surface

###############################################################################
cpos = [
    (7.656346967151718, -9.802071079151158, -11.021236183314311),
    (0.2224512272564101, -0.4594554282112895, 0.5549738359311297),
    (-0.6279216753504941, -0.7513057097368635, 0.20311105371647392),
]

surface.plot(cpos=cpos, opacity=0.75)


###############################################################################
# Create a voxel model of the bounding surface
voxels = pv.voxelize(surface, density=surface.length / 200)

p = pv.Plotter()
p.add_mesh(voxels, color=True, show_edges=True, opacity=0.5)
p.add_mesh(surface, color="lightblue", opacity=0.5)
p.show(cpos=cpos)


###############################################################################
# We could even add a scalar field to that new voxel model in case we
# wanted to create grids for modelling. In this case, let's add a scalar field
# for bone density noting:
voxels["density"] = np.full(voxels.n_cells, 3.65)  # g/cc
voxels

###############################################################################
voxels.plot(scalars="density", cpos=cpos)


###############################################################################
# A constant scalar field is kind of boring, so let's get a little fancier by
# added a scalar field that varies by the distance from the bounding surface.
voxels.compute_implicit_distance(surface, inplace=True)
voxels

###############################################################################
contours = voxels.contour(6, scalars="implicit_distance")

p = pv.Plotter()
p.add_mesh(voxels, opacity=0.25, scalars="implicit_distance")
p.add_mesh(contours, opacity=0.5, scalars="implicit_distance")
p.show(cpos=cpos)