Simple Logic Brick Question

Hi Blender Community,

I’m trying to make a simple animation involving a flexible tube and I can’t get the logic break to respond. I’m just trying to make the right arrow control the location motion of an empty hook. However, after I set the logic bricks up, the hook doesn’t move. I can drag the hook (named Vertex1) and it will flex the tube, but I am unable to get the keyboard to control this. Could someone please point me in the right direction?


I’ve attached the .blend file in case you would like to take a look. I’m using the newer version of Blender.
Test.blend (399 KB)

I think that your problems might not be as simple as just the logic brick.

  1. Your mesh, armature, and bezier curve all have some combination of transforms, rotations, and scales in Object space. Before you rig or parent objects you really need to ensure that all these transformation have been applied to your component parts.

  2. Your cylinder is not really what I would call a mesh. It has vertices and edges but no faces. So at best it will show as a wire frame and at worst it might not show in the BGE at all. Depends on how nice the game player is.

  3. Your objects and armatures are marked as “Static” in the physics. They need to be Dynamic and they need to have their “Ghost” settings setup correctly to keep them from colliding with each other.

  4. I have never tried using dynamic IK splines + hooks in the BGE but I know that they have some lag in how the evaluate in “normal” blender. I’m not sure that this will look correct in the BGE or if the hooks are going to play nice with the BGE at all.

I have attached a simplified .blend that just has a plane, a cube, and an Empty. The cube is parented to the empty and when you push the “up arrow” is will slide off your screen.

I would recommend the following.

  1. Clear the parenting on your Objects and cleanup your Object transformations.
  2. Parent a new cube to your “vertex 1” Empty and duplicate my setup just so you can see that the empty is moving.
  3. Put your rig back together and add the hooks, then try running it.


BGE_vertex_motion.blend (407 KB)

One more thought. You might want to ditch the IK spline + hooks and simply use a regular armature with b-bones. I’ve seen some tail rigs that used those and they came out looking pretty nice. You don’t get the full deform control of a bezier curve but they come very close and when used to deform a cylinder I think are actually more accurate.