def deriv(self, u, d=1):
"""
Evaluate a derivative on the curve.
:param float u: Curve parameter.
:param int d: Derivative to evaluate.
:return: Curve derivative.
:rtype: afem.geometry.entities.Vector
"""
from afem.geometry.entities import Vector
return Vector(self.object.DN(u, d).XYZ())
def to_vector(geom):
"""
Convert entity to a Vector if possible.
:param vector_like geom: An entity.
:return: The entity if already a Vector, or a new Vector if it is
vector_like.
:rtype: afem.geometry.entities.Vector
:raise TypeError: If entity cannot be converted to a Vector.
"""
return Vector.to_vector(geom)
def norm(self, u, v):
"""
Evaluate a normal on the surface.
:param float u: Surface u-parameter.
:param float v: Surface v-parameter.
:return: Surface normal.
:rtype: afem.geometry.entities.Vector
"""
from afem.geometry.entities import Vector
du = self.deriv(u, v, 1, 0)
dv = self.deriv(u, v, 0, 1)
return Vector(du.Crossed(dv).XYZ())
def deriv(self, u, v, nu, nv):
"""
Evaluate a derivative on the surface.
:param float u: Surface u-parameter.
:param float v: Surface v-parameter.
:param int nu: Derivative in u-direction.
:param int nv: Derivative in v-direction.
:return: Surface derivative.
:rtype: afem.geometry.entities.Vector
"""
from afem.geometry.entities import Vector
return Vector(self.object.DN(u, v, nu, nv).XYZ())