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I have an arbitrary edge that I would like to move so that it is in line with an arbitrary empty (in this case it will cross over the empty):

enter image description here

I assume that I will need to perhaps find the translation matrix of the 'line' representing the shortest distance between the edge and the empty but how would I do that using script?

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  • $\begingroup$ do you want to do this programmatically or are ways through the interface ok? also are you intending to do this in object mode or edit mode? $\endgroup$ – David Jun 29 '15 at 15:27
  • $\begingroup$ I need to do this programmatically. Probably in edit mode but for purposes of understanding the translation I don't think it would make too much difference :) --- I'm approaching a solution to the following question but need this translation to test it: blender.stackexchange.com/questions/32190/… $\endgroup$ – Eben Roux Jun 30 '15 at 3:56
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I think I may have sorted this now using Vector.project. For the script to work one would need to create a 2 vertex edge and call it line as well as adding an empty that is renamed empty (not Empty):

import bpy
from mathutils import Matrix

empty = bpy.data.objects["empty"]
line = bpy.data.objects["line"]

mw = line.matrix_world
ev = empty.location

# get the two line points in world space
lv0 = mw * line.data.vertices[0].co
lv1 = mw * line.data.vertices[1].co

# get the vector of the line
lv = (lv0 - lv1)

# get the translation between the original line and the line vector
# and apply that to the empty location to get the location of the 
# empty relative to the line vector
evt = Matrix.Translation(lv - lv0) * ev

# get the projection of the new empty location onto the line vector
# - `project` gets the perpendicular vector where `evt` intersects `lv`
evp = evt.project(lv)

# get the translation between the projected vector and the empty
tm = Matrix.Translation(evp - evt).inverted()

# now move the line
line.location = tm * line.location

I have created a simple add-on on GitHub to demonstrate the behaviour.

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I disagree. Select the edge you want in edit mode, press Ctrl+H> Hook to a New Object and it will create an empty and use its position for the edge.

Edit: Noted the purpose was something different. I'm still not sure you need to do this as a script. Take a look at the curve deformer.

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