153 lines
4.5 KiB
Python
153 lines
4.5 KiB
Python
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"""
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permutate.py
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-------------
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Randomly deform meshes in different ways.
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"""
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import numpy as np
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from . import transformations
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from . import triangles as triangles_module
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from . import util
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def transform(mesh, translation_scale=1000.0):
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"""
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Return a permutated variant of a mesh by randomly reording faces
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and rotatating + translating a mesh by a random matrix.
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Parameters
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----------
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mesh : trimesh.Trimesh
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Mesh, will not be altered by this function
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Returns
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----------
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permutated : trimesh.Trimesh
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Mesh with same faces as input mesh but reordered
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and rigidly transformed in space.
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"""
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# rotate and translate randomly
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matrix = transformations.random_rotation_matrix()
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matrix[0:3, 3] = (np.random.random(3) - 0.5) * translation_scale
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# randomly re-order triangles
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triangles = np.random.permutation(mesh.triangles).reshape((-1, 3))
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# apply rigid transform
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triangles = transformations.transform_points(triangles, matrix)
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# extract the class from the input object
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mesh_type = util.type_named(mesh, 'Trimesh')
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# generate a new mesh from the permutated data
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permutated = mesh_type(
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**triangles_module.to_kwargs(triangles.reshape((-1, 3, 3))))
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return permutated
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def noise(mesh, magnitude=None):
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"""
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Add gaussian noise to every vertex of a mesh, making
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no effort to maintain topology or sanity.
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Parameters
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----------
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mesh : trimesh.Trimesh
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Input geometry, will not be altered
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magnitude : float
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What is the maximum distance per axis we can displace a vertex.
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If None, value defaults to (mesh.scale / 100.0)
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Returns
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----------
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permutated : trimesh.Trimesh
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Input mesh with noise applied
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"""
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if magnitude is None:
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magnitude = mesh.scale / 100.0
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random = (np.random.random(mesh.vertices.shape) - .5) * magnitude
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vertices_noise = mesh.vertices.copy() + random
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# make sure we've re- ordered faces randomly
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triangles = np.random.permutation(vertices_noise[mesh.faces])
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mesh_type = util.type_named(mesh, 'Trimesh')
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permutated = mesh_type(**triangles_module.to_kwargs(triangles))
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return permutated
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def tessellation(mesh):
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"""
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Subdivide each face of a mesh into three faces with the new vertex
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randomly placed inside the old face.
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This produces a mesh with exactly the same surface area and volume
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but with different tessellation.
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Parameters
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------------
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mesh : trimesh.Trimesh
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Input geometry
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Returns
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----------
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permutated : trimesh.Trimesh
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Mesh with remeshed facets
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"""
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# create random barycentric coordinates for each face
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# pad all coordinates by a small amount to bias new vertex towards center
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barycentric = np.random.random(mesh.faces.shape) + .05
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barycentric /= barycentric.sum(axis=1).reshape((-1, 1))
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# create one new vertex somewhere in a face
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vertex_face = (barycentric.reshape((-1, 3, 1))
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* mesh.triangles).sum(axis=1)
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vertex_face_id = np.arange(len(vertex_face)) + len(mesh.vertices)
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# new vertices are the old vertices stacked on the vertices in the faces
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vertices = np.vstack((mesh.vertices, vertex_face))
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# there are three new faces per old face, and we maintain correct winding
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faces = np.vstack((np.column_stack((mesh.faces[:, [0, 1]], vertex_face_id)),
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np.column_stack(
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(mesh.faces[:, [1, 2]], vertex_face_id)),
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np.column_stack((mesh.faces[:, [2, 0]], vertex_face_id))))
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# make sure the order of the faces is permutated
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faces = np.random.permutation(faces)
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mesh_type = util.type_named(mesh, 'Trimesh')
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permutated = mesh_type(vertices=vertices,
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faces=faces)
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return permutated
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class Permutator:
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def __init__(self, mesh):
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"""
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A convenience object to get permutated versions of a mesh.
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"""
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self._mesh = mesh
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def transform(self, translation_scale=1000):
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return transform(
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self._mesh, translation_scale=translation_scale)
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def noise(self, magnitude=None):
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return noise(self._mesh, magnitude)
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def tessellation(self):
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return tessellation(self._mesh)
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try:
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# copy the function docstrings to the helper object
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Permutator.noise.__doc__ = noise.__doc__
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Permutator.transform.__doc__ = transform.__doc__
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Permutator.tessellation.__doc__ = tessellation.__doc__
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except AttributeError:
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# no docstrings in Python2
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pass
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