I have two cylinders, one is the puck, other is the handle. The handle is child of the puck. They both have dynamic physics. I use python to define their motion. As soon as I hit p and enter gaming/testing mode, their locations are changed. But the handle has more dramatical location change than the puck.

enter image description here

Here is two photos of before and after hitting p:


enter image description here


enter image description here

I cannot figure out why this sudden change of location and getting compressed in y direction.

Here is my script:

import bge

def main():
    cont = bge.logic.getCurrentController()
    scene = bge.logic.getCurrentScene()
    keyboard = bge.logic.keyboard
    puck = cont.owner

    # sensors
    bottom_edge_collision = cont.sensors["bottom_edge"]

    # keys
    r_pressed = bge.logic.KX_INPUT_JUST_ACTIVATED == keyboard.events[bge.events.RKEY]

    if r_pressed:
        print("rsrt", puck.localPosition)


Here is my blend file: https://drive.google.com/drive/folders/1dcXSZ7HHZH9h8f6KFJWUsVmuRl69o6bd?usp=sharing

  • $\begingroup$ You do not need "main()" and "def main()". It makes the code harder to read. $\endgroup$ – Monster Jan 16 '18 at 5:09

Without seeing your blend file we can only guess. The most likely candidate is a non-unit scale. Select the objects, press CTRL+A and choose "Scale". This applies the object-level scale factor to the mesh itself, and resets the object-level scale to (1, 1, 1).


This sounds like an old bug of Blender (which can't be compensated by the BGE).

in Blender:

  • Unparent the objects.
  • Reset both objects to the scene origin (Rot, Pos, Scale).
  • Parent them together
  • move the parent to the desired location.
  • $\begingroup$ When I use no scale, your solution is perfect. But when I make the handle slimmer, same problem occurs. How can I make a thin-long handle other than using scale? $\endgroup$ – Saba Jan 16 '18 at 14:01
  • $\begingroup$ As mentioned in the other answer, apply the scale, which deforms the vertices rather than the object. $\endgroup$ – Monster Jan 17 '18 at 13:47

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