# Collision
# =========

# Perform a collision detection between two meshes.
# This example use the `collision()`
# filter to detect the faces from one sphere colliding with another
# sphere.

# NOTE:
#     Due to the nature of the vtkCollisionDetectionFilter,
#     repeated uses of this method will be slower that using the
#     vtkCollisionDetectionFilter directly.  The first
#     update of the filter creates two instances of vtkOBBTree,
#     which can be subsequently updated by modifying the transform or
#     matrix of the input meshes.
#     This method assumes no transform and is easier to use for
#     single collision tests, but it is recommended to use a
#     combination of `pyvista` and `vtk` for rapidly computing
#     repeated collisions.  See the Collision Detection Example

import numpy as np
import pyvista as pv

pv.set_plot_theme('document')

# Create the main mesh and the secondary "moving" mesh
# Collision faces will be plotted on this sphere, and to do so we
# initialize an initial `"collisions"` mask.
sphere0 = pv.Sphere()
sphere0['collisions'] = np.zeros(sphere0.n_cells, dtype=bool)

# This mesh will be the moving mesh
sphere1 = pv.Sphere(radius=0.6, center=(-1, 0, 0))

# Set up the plotter open a movie, and write a frame after moving the sphere.
pl = pv.Plotter()
pl.enable_hidden_line_removal()
pl.add_mesh(sphere0, scalars='collisions', show_scalar_bar=False, cmap='bwr')
pl.camera_position = 'xz'
pl.add_mesh(sphere1, style='wireframe', color='green', line_width=5)

# for this example
pl.open_gif('collision_movie.gif')

# alternatively, to disable movie generation:
# pl.show(auto_close=False, interactive=False)

delta_x = 0.1
for _ in range(int(2 / delta_x)):
    sphere1.translate([delta_x, 0, 0], inplace=True)
    col, n_contacts = sphere0.collision(sphere1)

    collision_mask = np.zeros(sphere0.n_cells, dtype=bool)
    if n_contacts:
        collision_mask[col['ContactCells']] = True
    sphere0['collisions'] = collision_mask
    pl.write_frame()

    # alternatively, disable movie plotting and simply render the image
    # pl.render()

pl.close()

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