mirror of
https://github.com/wassname/simpeg.git
synced 2026-06-28 03:19:21 +08:00
Lindsey Heagy
62 lines
2.2 KiB
Python
62 lines
2.2 KiB
Python
import numpy as np
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from SimPEG.Utils import mkvc
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def rotationMatrixFromNormals(v0,v1,tol=1e-20):
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"""
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Performs the minimum number of rotations to define a rotation from the direction indicated by the vector n0 to the direction indicated by n1.
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The axis of rotation is n0 x n1
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https://en.wikipedia.org/wiki/Rodrigues%27_rotation_formula
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:param numpy.array v0: vector of length 3
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:param numpy.array v1: vector of length 3
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:param tol = 1e-20: tolerance. If the norm of the cross product between the two vectors is below this, no rotation is performed
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:rtype: numpy.array, 3x3
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:return: rotation matrix which rotates the frame so that n0 is aligned with n1
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"""
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# ensure both n0, n1 are vectors of length 1
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assert len(v0) == 3, "Length of n0 should be 3"
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assert len(v1) == 3, "Length of n1 should be 3"
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# ensure both are true normals
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n0 = v0*1./np.linalg.norm(v0)
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n1 = v1*1./np.linalg.norm(v1)
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n0dotn1 = n0.dot(n1)
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# define the rotation axis, which is the cross product of the two vectors
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rotAx = np.cross(n0,n1)
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if np.linalg.norm(rotAx) < tol:
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return np.eye(3,dtype=float)
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rotAx *= 1./np.linalg.norm(rotAx)
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cosT = n0dotn1/(np.linalg.norm(n0)*np.linalg.norm(n1))
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sinT = np.sqrt(1.-n0dotn1**2)
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ux = np.array([[0., -rotAx[2], rotAx[1]], [rotAx[2], 0., -rotAx[0]], [-rotAx[1], rotAx[0], 0.]],dtype=float)
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return np.eye(3,dtype=float) + sinT*ux + (1.-cosT)*(ux.dot(ux))
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def rotatePointsFromNormals(XYZ,n0,n1,x0=np.r_[0.,0.,0.]):
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"""
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rotates a grid so that the vector n0 is aligned with the vector n1
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:param numpy.array n0: vector of length 3, should have norm 1
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:param numpy.array n1: vector of length 3, should have norm 1
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:param numpy.array x0: vector of length 3, point about which we perform the rotation
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:rtype: numpy.array, 3x3
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:return: rotation matrix which rotates the frame so that n0 is aligned with n1
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"""
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R = rotationMatrixFromNormals(n0, n1)
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assert XYZ.shape[1] == 3, "Grid XYZ should be 3 wide"
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assert len(x0) == 3, "x0 should have length 3"
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X0 = np.ones([XYZ.shape[0],1])*mkvc(x0)
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return (XYZ - X0).dot(R.T) + X0 # equivalent to (R*(XYZ - X0)).T + X0 |