Rotate bmesh around Vector with Python

Question

I try to rotate a bmesh around a vector as axis.

vec = vert1.co + vert2.co
rot = mathutils.Euler(vec/max(vec)).to_matrix()
bmesh.ops.rotate(bm, cent=vert2.co, matrix=rot, verts=bm.verts, space=objCT.matrix_world)

But unfortunately it rotates in a strange way. How could I fix this?

Answer 1

Rotate bmesh vertices around a vector defined by two selected verts.

Test script, rotates 45 degrees around the vector defined by two selected verts. Select two vertices and run script. Running 8 times should rotate the full sweep.

import bpy
import bmesh
context = bpy.context
from mathutils import Matrix
from math import radians

obj = context.edit_object
me = obj.data
bm = bmesh.from_edit_mesh(me)

# have 2 verts selected.
v1, v2, *_ = (v for v in bm.verts if v.select)
axis = (v2.co - v1.co).normalized()
rot = Matrix.Rotation(radians(45), 4, axis)
bmesh.ops.rotate(bm, cent=v2.co, matrix=rot, verts=bm.verts)

me.update()

Note: because our rotation matrix is using an axis and both v1 and v2 are on the axis, either (or any point on) can be used for cent property of operator . The centre point would be calculated via v1.co + axis / 2 or (v1.co + v2.co) / 2

Answer 2

I am trying to do something similar but running into problems, so this is not an answer but a question about a slightly more advanced usage of this script.

I am also trying to rotate bmesh around Vector, but I only want to rotate the selected faces, not the whole mesh, around the Active Edge. Also, before that, I want to do an extrusion with 0 distance, so that the rotation kind of has a new segment. My problem is that I get this extra geometry. I read that I am supposed to delete the geometry that bmesh.ops.extrude_face_region() uses to make new geometry. I have tried that as well but blender crashes every time when I use bmesh.ops.delete(). So I have that part commented out in my script. Could anyone help me avoid the weird extra geometry when using this script. Again, this will work with copy-past into the Text Editor and Run Script, while having a mesh in Edit mode with one Active Edge.

import bpy
import bmesh
context = bpy.context
from mathutils import Matrix
from math import radians

obj = context.edit_object
me = obj.data
bm = bmesh.from_edit_mesh(me)
selected = [v for v in bm.verts if v.select]
face_sel = [f for f in bm.faces if f.select]

edge = bm.select_history.active
axis_rot = (edge.verts[0].co - edge.verts[1].co).normalized()
rot = Matrix.Rotation(radians(45), 4, axis_rot)

r = bmesh.ops.extrude_face_region(bm, geom=face_sel)

# DEL_VERTS = 1
# DEL_EDGES = 2
# DEL_ONLYFACES = 3
# DEL_EDGESFACES = 4
# DEL_FACES = 5
# DEL_ALL = 6
# DEL_ONLYTAGGED = 7

# bmesh.ops.delete(bm, geom=face_sel, context=DEL_FACES)

bmesh.ops.rotate(bm, cent=edge.verts[0].co, matrix=rot, verts=selected)


me.update()