def test_normal_vector_for_3_points():
# normal_vector_3p(a, b, c)
# a->b = v1
# a->c = v2
o = Vector(0, 0, 0)
assert normal_vector_3p(o, X_AXIS, Y_AXIS) == Z_AXIS
assert normal_vector_3p(o, Y_AXIS, X_AXIS) == -Z_AXIS
assert normal_vector_3p(o, Z_AXIS, X_AXIS) == Y_AXIS
assert normal_vector_3p(o, X_AXIS, Z_AXIS) == -Y_AXIS
assert normal_vector_3p(o, Y_AXIS, Z_AXIS) == X_AXIS
assert normal_vector_3p(o, Z_AXIS, Y_AXIS) == -X_AXIS
def render_normals(
self,
layout: "GenericLayoutType",
length: float = 1,
relative=True,
dxfattribs=None,
):
"""Render face normals as :class:`~ezdxf.entities.Line` entities into
`layout`, useful to check orientation of mesh faces.
Args:
layout: :class:`~ezdxf.layouts.BaseLayout` object
length: visual length of normal, use length < 0 to point normals in
opposite direction
relative: scale length relative to face size if ``True``
dxfattribs: dict of DXF attributes e.g. ``{'layer': 'normals', 'color': 6}``
"""
dxfattribs = dict(dxfattribs) if dxfattribs else {}
for face in self.faces_as_vertices():
count = len(face)
if count < 3:
continue
center = sum(face) / count
i = 0
n = NULLVEC
while i <= count - 3:
n = normal_vector_3p(face[i], face[i + 1], face[i + 2])
if n != NULLVEC: # not colinear vectors
break
i += 1
if relative:
_length = (face[0] - center).magnitude * length
else:
_length = length
layout.add_line(center,
center + n * _length,
dxfattribs=dxfattribs)
def test_normal_vector_for_3_points(a, b, c, r):
assert normal_vector_3p(a, b, c) == r