# stop transformation matrix from scaling mesh

I’m using some code from LINK to create a transformation matrix to align shapes on faces of other shapes. for some reason it also scales the object up, and I have no idea why. I’m not at all familiar with transformation matrices. here is the code:

``````import bpy
import mathutils
import pprint
import bmesh
from mathutils import *

def make_matrix(v1, v2, v3):
a = v2-v1
b = v3-v1

c = a.cross(b)
if c.magnitude&gt;0:
c = c.normalized()
else:
raise BaseException("A B C are colinear")

b2 = c.cross(a).normalized()
a2 = a.normalized()
m = Matrix([a2, b2, c]).transposed()
s = a.magnitude
m = Matrix.Translation(v1) * Matrix.Scale(s,4) * m.to_4x4()

return m

bm = bmesh.from_edit_mesh(bpy.context.object.data)

selected_face = [f for f in bm.faces if f.select]
selected_face = selected_face[0]        # list has only one item. this makes it a single object instead of a list of one.

trans_matrix = make_matrix(selected_face.verts[0].co, selected_face.verts[1].co, selected_face.verts[2].co)

vert1position = (1, 1, 2)
vert2position = (-1, 1, 2)
vert3position = (-1, -1, 2)
vert4position = (1, -1, 2)
vert5position = (1, 1, 0)
vert6position = (-1, 1, 0)
vert7position = (-1, -1, 0)
vert8position = (1, -1, 0)

vert = []

# vertices
bm.verts.ensure_lookup_table()
vert.append(bm.verts.new((vert1position)))
vert.append(bm.verts.new((vert2position)))
vert.append(bm.verts.new((vert3position)))
vert.append(bm.verts.new((vert4position)))
vert.append(bm.verts.new((vert5position)))
vert.append(bm.verts.new((vert6position)))
vert.append(bm.verts.new((vert7position)))
vert.append(bm.verts.new((vert8position)))

# edges
bm.edges.ensure_lookup_table()
bm.edges.new((vert[0], vert[1]))
bm.edges.new((vert[1], vert[2]))
bm.edges.new((vert[2], vert[3]))
bm.edges.new((vert[3], vert[0]))
bm.edges.new((vert[4], vert[5]))
bm.edges.new((vert[5], vert[6]))
bm.edges.new((vert[6], vert[7]))
bm.edges.new((vert[7], vert[4]))
bm.edges.new((vert[0], vert[4]))
bm.edges.new((vert[1], vert[5]))
bm.edges.new((vert[2], vert[6]))
bm.edges.new((vert[3], vert[7]))

bmesh.ops.transform(bm, matrix= trans_matrix, verts= bm.verts[-8:])
``````

if you want to run this code, you need a triangular face of a mesh selected for it to work properly.

SOLVED: Matrix.Scale(s,4) -> Matrix.Scale(1,4)

Matrix.Scale(1,4) is the identity matrix. You can omit that entirely, you’re essentially multiplying by 1.