.. DO NOT EDIT.
.. THIS FILE WAS AUTOMATICALLY GENERATED BY SPHINX-GALLERY.
.. TO MAKE CHANGES, EDIT THE SOURCE PYTHON FILE:
.. "gallery/scene/face_picking.py"
.. LINE NUMBERS ARE GIVEN BELOW.

.. only:: html

    .. note::
        :class: sphx-glr-download-link-note

        :ref:`Go to the end <sphx_glr_download_gallery_scene_face_picking.py>`
        to download the full example code.

.. rst-class:: sphx-glr-example-title

.. _sphx_glr_gallery_scene_face_picking.py:


Picking Faces from a Mesh
=========================

Demonstrates how to identify (pick) individual faces on a mesh.

Arguments:
* --mesh - Path to a mesh file (OBJ/OBJ.GZ) [optional]

Controls:
* p  - Toggle face picking view - shows the colors encoding face ID
* r  - Clear painted faces
* s  - Cycle shading modes (None, 'flat', 'smooth')
* w  - Toggle wireframe

.. GENERATED FROM PYTHON SOURCE LINES 22-150



.. image-sg:: /gallery/scene/images/sphx_glr_face_picking_001.png
   :alt: face picking
   :srcset: /gallery/scene/images/sphx_glr_face_picking_001.png
   :class: sphx-glr-single-img


.. rst-class:: sphx-glr-script-out

 .. code-block:: none

    Downloading data from https://raw.githubusercontent.com/vispy/demo-data/main/orig/triceratops.obj.gz (141 kB)

    [..................                      ] 45.52059 | downloading   
    [....................................    ] 91.04119 / downloading   
    [........................................] 100.00000 - downloading   
    File saved as /home/runner/.vispy/data/orig/triceratops.obj.gz.







|

.. code-block:: Python

    import argparse
    import itertools
    import time

    import numpy as np

    from vispy import app, scene
    from vispy.io import read_mesh, load_data_file
    from vispy.scene.visuals import Mesh
    from vispy.scene import transforms
    from vispy.visuals.filters import ShadingFilter, WireframeFilter, FacePickingFilter


    parser = argparse.ArgumentParser()
    default_mesh = load_data_file('orig/triceratops.obj.gz')
    parser.add_argument('--mesh', default=default_mesh)
    args, _ = parser.parse_known_args()

    vertices, faces, _normals, _texcoords = read_mesh(args.mesh)

    canvas = scene.SceneCanvas(keys='interactive', bgcolor='white')
    view = canvas.central_widget.add_view()

    view.camera = 'arcball'
    view.camera.depth_value = 1e3

    # Create a colored `MeshVisual`.
    face_colors = np.tile((0.5, 0.0, 0.5, 1.0), (len(faces), 1))
    mesh = Mesh(
        vertices,
        faces,
        face_colors=face_colors.copy()
    )
    mesh.transform = transforms.MatrixTransform()
    mesh.transform.rotate(90, (1, 0, 0))
    mesh.transform.rotate(-45, (0, 0, 1))
    view.add(mesh)

    # Use filters to affect the rendering of the mesh.
    wireframe_filter = WireframeFilter()
    shading_filter = ShadingFilter()
    face_picking_filter = FacePickingFilter()
    mesh.attach(wireframe_filter)
    mesh.attach(shading_filter)
    mesh.attach(face_picking_filter)


    def attach_headlight(view):
        light_dir = (0, 1, 0, 0)
        shading_filter.light_dir = light_dir[:3]
        initial_light_dir = view.camera.transform.imap(light_dir)

        @view.scene.transform.changed.connect
        def on_transform_change(event):
            transform = view.camera.transform
            shading_filter.light_dir = transform.map(initial_light_dir)[:3]


    attach_headlight(view)

    shading = itertools.cycle(("flat", "smooth", None))
    shading_filter.shading = next(shading)


    throttle = time.monotonic()


    @canvas.events.mouse_move.connect
    def on_mouse_move(event):
        global throttle
        # throttle mouse events to 50ms
        if time.monotonic() - throttle < 0.05:
            return
        throttle = time.monotonic()

        # adjust the event position for hidpi screens
        render_size = tuple(d * canvas.pixel_scale for d in canvas.size)
        x_pos = event.pos[0] * canvas.pixel_scale
        y_pos = render_size[1] - (event.pos[1] * canvas.pixel_scale)

        # render a small patch around the mouse cursor
        restore_state = not face_picking_filter.enabled
        face_picking_filter.enabled = True
        mesh.update_gl_state(blend=False)
        picking_render = canvas.render(
            region=(x_pos - 1, y_pos - 1, 3, 3),
            size=(3, 3),
            bgcolor=(0, 0, 0, 0),
            alpha=True,
        )
        if restore_state:
            face_picking_filter.enabled = False
        mesh.update_gl_state(blend=not face_picking_filter.enabled)

        # unpack the face index from the color in the center pixel
        face_idx = (picking_render.view(np.uint32) - 1)[1, 1, 0]

        if face_idx > 0 and face_idx < len(face_colors):
            # this may be less safe, but it's faster than set_data
            mesh.mesh_data._face_colors_indexed_by_faces[face_idx] = (0, 1, 0, 1)
            mesh.mesh_data_changed()


    @canvas.events.key_press.connect
    def on_key_press(event):
        if event.key == 'p':
            face_picking_filter.enabled = not face_picking_filter.enabled
            mesh.update_gl_state(blend=not face_picking_filter.enabled)
            mesh.update()

        if event.key == 'r':
            mesh.set_data(vertices, faces, face_colors=face_colors)

        if event.key == 's':
            shading_filter.shading = next(shading)
            mesh.update()

        if event.key == 'w':
            wireframe_filter.enabled = not wireframe_filter.enabled
            mesh.update()


    canvas.show()


    if __name__ == "__main__":
        print(__doc__)
        app.run()


.. rst-class:: sphx-glr-timing

   **Total running time of the script:** (0 minutes 1.132 seconds)


.. _sphx_glr_download_gallery_scene_face_picking.py:

.. only:: html

  .. container:: sphx-glr-footer sphx-glr-footer-example

    .. container:: sphx-glr-download sphx-glr-download-jupyter

      :download:`Download Jupyter notebook: face_picking.ipynb <face_picking.ipynb>`

    .. container:: sphx-glr-download sphx-glr-download-python

      :download:`Download Python source code: face_picking.py <face_picking.py>`


.. only:: html

 .. rst-class:: sphx-glr-signature

    `Gallery generated by Sphinx-Gallery <https://sphinx-gallery.github.io>`_