Hi @BigEfrom84,

Maybe have `bezier_multi_seg`

return not just the bezier coordinate and tangent, but the local right, and up for that point on the curve also? I added a helper function that normalizes the tangent and finds the right vector relative to a reference / world up. The right vector is rotated by the tilt around the forward axis. Last, the local up vector is found with the cross product.

```
def axes(tangent, tilt=0.0, ref_up=Vector((0.0, 0.0, 1.0))):
tan_norm = tangent.normalized()
right = tan_norm.cross(ref_up)
rot = Quaternion(tangent, tilt)
right = rot * right
right.normalize()
up = right.cross(tangent)
up.normalize()
return {'right': right, 'up': up, 'forward': tan_norm}
```

To update the relevant bit of the `bezier_multi_seg`

function:

```
def bezier_multi_seg(knots=[], step=0.0, closed_loop=False,
ref_up=Vector((0.0, 0.0, 1.0))):
#...
tangent = bezier_tangent(pt0=pt0, pt1=pt1, pt2=pt2, pt3=pt3, step=u)
tilt = (1.0 - u) * a.tilt + u * b.tilt
ax = axes(tangent, tilt, ref_up)
return {'coord': coord,
'right': ax['right'],
'forward': ax['forward'],
'up': ax['up']}
```

Then you could build a quaternion from the three axes.

```
i = coord_tangent['right']
j = coord_tangent['forward']
k = coord_tangent['up']
rotation = Matrix([
[i.x, j.x, k.x, 0.0],
[i.y, j.y, k.y, 0.0],
[i.z, j.z, k.z, 0.0],
[0.0, 0.0, 0.0, 1.0]
]).to_quaternion()
coaster.rotation_quaternion = rotation
```

Sorry, I can’t upload a .blend file attachment atm, otherwise I would.