path following camera

I'm new to scripting inside blender (two days). I have a camera folowing a path (a circle).

I have written the following code to get the location and rotation for each frame and write it to a file:

import bpy


for f in range(bpy.context.scene.frame_start,bpy.context.scene.frame_end):
    for obj in bpy.context.selected_objects:
        transformMetrix.write('\n'+ str(f)+'\n')
        transformMetrix.write('Location : ' + str(obj.location.x) +' '+ str(obj.location.y) +' '+ str(obj.location.z) +'\n')
        transformMetrix.write('rotation : ' + str(obj.rotation_euler.x) +' '+str(obj.rotation_euler.y) +' '+str(obj.rotation_euler.z)+'\n')
        transformMetrix.write('scale : ' + str(int(obj.scale.x)) +' '+str(int(obj.scale.y))+' '+str(int(obj.scale.z)) +'\n')


When I play and run the script I only get the same rotation and location matrix for every frame.

enter image description here

What am I doing wrong here?

Then I tried to put above code inside a function and append it to a handler, but I still get the same output:

  • 2
    $\begingroup$ Looks like to me that you just iterate through the frames but don't ask where the object is in a certain frame, just where the object is (that will be frame 0 or 1 w/e) $\endgroup$
    – WhatAMesh
    Aug 20 '18 at 17:27
  • $\begingroup$ Get the fcurves for the animation and use fcurve.evaluate() to get the values at a given frame. $\endgroup$
    – sambler
    Aug 22 '18 at 4:34

You have to change the frame in your for-loop via Scene.frame_set():


By the way, I would not use obj.location, rotation_euler etc. because they do not contain the final location, rotation and so on. For example, parent your camera to an object, then rotate the object - the camera.rotation_euler will not change.

You should use obj.matrix_world instead (if you need it separated, decompose this matrix with to_location, to_euler etc.)

  • 4
    $\begingroup$ Note too the decompose method loc, rot, scale = obj.matrix_world.decompose() $\endgroup$
    – batFINGER
    Aug 21 '18 at 15:44
  • $\begingroup$ Thank you for the answer. Adding bpy.context.scene.frame_set(f) for the initial code didn't gave me the expected output. it was same as the result I posted. I think this is because of the issue mentioned here right? but setting the frame bpy.context.scene.frame_set(f) and taking the transform metrix with obj.matrix_world worked. $\endgroup$ Aug 22 '18 at 21:11

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