Hello,
I am struggling the past two weeks with the following problem. I have tried
different approaches but none of them worked so far, therefore I would like
your help/advice.
I have created a geometry in Blender, for instance a BezierCurve, and I have
connected it with a Lattice modifier and a vertex group. So, once I move one
point or a family of points of the lattice, the geometry shape changes as well.
Is there a way to get the displacement vector, i.e. how much each geometry
point (neither the lattice points nor the BezierCurce control points) has moved?
i. The only way I have found so far is exporting the new
geometry to stl format and comparing the old and the new (after applying
bpy.ops.transform.translate()) stl files. The problem is that the stl files are
not consistent.
ii. I have tried using the python API to subtract the
vertices of bpy.data.objects["BezierCurve"].data.vertices before and after
applying bpy.ops.transform.translate(), but the list of the vectors with the
vertice coordinates is identical before and after applying the lattice
modifier. I also tried getting the coordinates of the geometry shape from the
mesh, once in the beginning and once after the lattice translation, but the
results was the same:
bm = bmesh.new()
bm.from_mesh(bpy.data.objects["BezierCurve"].data)
vertices = bm.verts
original_positions = [list(vertex.co) for vertex in vertices]
Surprisingly enough, when I tried to plot the range of each coordinate, i.e the
min, max values of the x,y,z coordinates of the vertices, they are not the same
as the ones noticed when I do a visual inspection of the geometry, i.e with
ParaView.
iii. Finally, I tried getting the necessary functions from the
blender source code in c, c++ but I don't think this is the correct way. To
begin with, I couldn't find another executable apart from ./blender to run and
test some isolated functionalities. Secondly, it wasn't so easy to grab and
extract the relevant functions BKE_lattice_deform_coords_with_mesh, deformVerts
to a c++ file outside blender and perform the necessary operations.
I feel like the best way to proceed is (ii) but I cannot get why the vertices
location is not updated although the exported stl looks different. I tried
doing:
bpy.ops.object.modifier_apply(modifier=bpy.data.objects["BezierCurve"].name)
bpy.data.objects["BezierCurve"].data.update()
after applying applying bpy.ops.transform.translate().
Any advice or idea is more than welcome.
Thanks and kind regards,
Nikos
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