I want to animate a body using an external file with x, y, z coordinates and quaternion data.

In the file every entry [x,y,x,q0,q1,q2,q3] represents a frame to be rendered.

I heard about Blender and its compatibility with python and, since I am a python user, I would like to know if it is possible to do what I mentioned above and how to do it.

Thanks in advance.


It's very possible, and doesn't even sound difficult to do.

Make sure Object.rotation_mode is 'QUATERNION' (once for the object):

ob = bpy.context.object # active object, assuming there is one
ob.rotation_mode = 'QUATERNION'

Reading the file:

import bpy
from mathutils import Vector, Quaternion

file = open("input.txt", "r")
for line in file:
    x, y, z, q0, q1, q2, q3 = line.strip(" \t\r\n[]").split(",")
    loc = float(x), float(y), float(z)
    quat = float(q0), float(q1), float(q2), float(q3)

    # Or cast to Vector / Quaternion type if you need any methods of them later
    #loc = Vector(loc)
    #quat = Quaternion(quat)

I assume line 1 in the file is meant to be the first frame in Blender and so on. Let's keep track of the line number:

for i, line in enumerate(file, 1):

Assign the location and the rotation in our for-loop:

    ob.location = loc
    ob.rotation_quaternion = quat

and insert keyframes for frame i:

    ob.keyframe_insert('location', frame=i)
    ob.keyframe_insert('rotation_quaternion', frame=i)

Finally, we close the file:


For a better performaning way to animate with python, see:


  • $\begingroup$ Thank you so much for your help. It works! I just want to add something: loc and quat can't have string entries so they must be transform to float. $\endgroup$ – Tharek M Feb 12 '14 at 0:33
  • $\begingroup$ Geez! Totally forgot to cast to numbers, edited my post. float() accepts any kind of floating point notation: 0.1, .1, 1., 1e-3. For integer values, you would use int() (no rounding if used on floats, use math.round() instead if needed). Properties like Object.location accept several types without explicit casting, Vector, int, float... $\endgroup$ – CoDEmanX Feb 12 '14 at 0:41

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.