def from_factors(cls, factors, frame=None):
"""Construct a scale transformation from scale factors.
Parameters
----------
factors : list of float
The scale factors along X, Y, Z.
frame : :class:`compas.geometry.Frame`, optional
The anchor frame for the scaling transformation.
Defaults to ``None``.
Returns
-------
Scale
A scale transformation.
Examples
--------
>>> point = Point(2, 5, 0)
>>> frame = Frame(point, (1, 0, 0), (0, 1, 0))
>>> points = [point, Point(2, 10, 0)]
>>> S = Scale.from_factors([2.] * 3, frame)
>>> [p.transformed(S) for p in points]
[Point(2.000, 5.000, 0.000), Point(2.000, 15.000, 0.000)]
"""
S = cls()
if frame:
Tw = matrix_from_frame(frame)
Tl = matrix_inverse(Tw)
Sc = matrix_from_scale_factors(factors)
S.matrix = multiply_matrices(multiply_matrices(Tw, Sc), Tl)
else:
S.matrix = matrix_from_scale_factors(factors)
return S
def __init__(self, matrix=None):
if matrix:
scale, _, _, _, _ = decompose_matrix(matrix)
check = matrix_from_scale_factors(scale)
if not allclose(flatten(matrix), flatten(check)):
raise ValueError('This is not a proper scale matrix.')
super(Scale, self).__init__(matrix=matrix)
def scale_points_xy(points, scale):
"""Scale points in the XY plane.
Parameters
----------
points : list of point
A list of points.
scale : float
A scaling factor.
Returns
-------
list of point
The scaled points in the XY plane (Z=0).
Examples
--------
>>>
"""
T = matrix_from_scale_factors([scale, scale, 0])
return transform_points(points, T)
def scale_points_xy(points, scale):
"""Scale points in the XY plane.
Parameters
----------
points : sequence[[float, float, float] | :class:`compas.geometry.Point`]
A list of points.
scale : float
A scaling factor.
Returns
-------
list[[float, float, float]]
The scaled points in the XY plane (Z=0).
Examples
--------
>>>
"""
T = matrix_from_scale_factors([scale, scale, 0])
return transform_points(points, T)
def __init__(self, scale_factors):
self.matrix = matrix_from_scale_factors(scale_factors)
def test_matrix_from_scale_factors():
Sc = matrix_from_scale_factors([1, 2, 3])
assert Sc == [[1.0, 0.0, 0.0, 0.0], [0.0, 2.0, 0.0, 0.0], [0.0, 0.0, 3.0, 0.0], [0.0, 0.0, 0.0, 1.0]]
