vispy.visuals.mesh_normals module

A visual for displaying mesh normals as lines.

class vispy.visuals.mesh_normals.MeshNormalsVisual(meshdata, primitive='face', length=None, length_method='median_edge', length_scale=1.0, **kwargs)[source]

Bases: vispy.visuals.line.line.LineVisual

Display mesh normals as lines.

meshdatainstance of MeshData

The mesh data.

primitive{‘face’, ‘vertex’}

The primitive type on which to compute and display the normals.

lengthNone or float or array-like, optional

The length(s) of the normals. If None, the length is computed with length_method.

length_method{‘median_edge’, ‘max_extent’}, default=’median_edge’

The method to compute the length of the normals (when length=None). Methods: ‘median_edge’, the median edge length; ‘max_extent’, the maximum side length of the bounding box of the mesh.

length_scalefloat, default=1.0

A scale factor applied to the length computed with length_method.

**kwargsdict, optional

Extra arguments to define the appearance of lines. Refer to LineVisual.


Create a MeshVisual on which to display the normals and get the MeshData:

>>> mesh = MeshVisual(vertices=vertices, faces=faces, ...)
>>> meshdata = mesh.mesh_data

Create a visual for the mesh normals:

>>> normals = MeshNormalsVisual(meshdata)

Display the face normals:

>>> MeshNormalsVisual(..., primitive='face')
>>> MeshNormalsVisual(...)  # equivalent (default values)

Display the vertex normals:

>>> MeshNormalsVisual(..., primitive='vertex')

Fixed length for all normals:

>>> MeshNormalsVisual(..., length=0.25)

Individual length per normal:

>>> lengths = np.array([0.5, 0.2, 0.7, ..., 0.7], dtype=float)
>>> MeshNormalsVisual(..., length=lengths)
>>> assert len(lengths) == len(faces)  # for face normals
>>> assert len(lengths) == len(vertices)  # for vertex normals

Normals at about the length of a triangle:

>>> MeshNormalsVisual(..., length_method='median_edge', length_scale=1.0)
>>> MeshNormalsVisual(...)  # equivalent (default values)

Normals at about 10% the size of the mesh:

>>> MeshNormalsVisual(..., length_method='max_extent', length_scale=0.1)