Plunger, again


I am new to Blender and have been playing around with the idea of animating a plunger, as in here I have a model, I have a rig, but I don’t seem to be able to marry them. The movement of the model is not smooth. So I was wondering if any of you guys could lay down a road map of how you would go about it.

My biggest problem is the rounded rubber bottom bit. Even after I assigned vertices manually to the rig, the movement is not smooth. It seems that because vertices of the curved surface are not all equally far away from the bone that the model gets squashed in the oddest places, if you know what I mean. My rig consists of several bones in a straight line for the stick and four sort of spider legs at the bottom. Only moving the rig looks very much like what I want to achieve.

I want to personalise the plunger, in the end it should happily hop across the scene. Ever saw that desktop lamp which Pixar uses in the logo? Guess what inspired me.

I attached piccies of the model (which is very straight forward) and the rig. The four vertical bones at the end of the legs are the IK targets, the center bone realises the floor constraint. Again, any pointers would be greatly appreciated, let me know if you need more infos.



IMHO, you shouldn’t be using an armature for the bottom of the plunger. I would look into using a lattice or a different kind of deformation.

our shape keys

QFT. A lattice for something this simplistic would probably be your best friend.

Ahhh, shape keys, lattice deformation… a whole new world out there.

Cheers for the help

have fun
but if you get stuck you know where to ask :slight_smile:

Speaking of being stuck…

I spend some time getting to know lattices and although I seem to understand what they do and what you can achieve with them, I do not see how they help me. Certainly, I can squash the bottom rubber bit like the ball in the famous ball bouncing tutorial. However, everybody who has placed a plunger on the kitchen table (and I encourage you all to do it now) will know that this is absolutely not what the real thing will do. Instead, the outer edge of the sucker will stay essentially intact whereas the middle bit sinks in - if you know what I mean. And so far I have not figured out how I can achieve that with a lattice. The reason is that I cannot seem to change vertices of the lattice as part of an animation, i.e. so

  1. add plunger mesh
  2. add lattice
  3. add lattice modifier to plunger mesh
  4. insert keyframe
  5. move some frames in the future
  6. edit the lattice, i.e. go inte Edit Mode and change positions of lattice vertices
  7. insert keyframe

If you follow the above steps, the deformation of the lattice itself and hence the mesh will not be animated. This might be because that is not the way things work. If that is indeed the way things work then I do not see how you can make the sucker behave naturally with only scaling, rotating and translating the entire lattice.

I hope I am missing something and somebody can shed some light on these issues.

2 hours and a bottle of wine later I have climbed quite a learning curve and realised that combining a lattice with shape keys is the way forward. I (almost) know how to handle both now.


Is a stretch-to constraint maybe what you are looking for?

If I want to deform a round thing like the sucker with a square thing like the lattice, I naturally run into problems, i.e. that the deformation does not look natural but, well, square. Are the following the only two options?

  1. Increase number of lattice vertices to something incredible high, so that the spacing of the lattice is the same or smaller than the spacing of the model mesh.

  2. Move the lattice vertices by hand so that they form a circular lattice.

Is 2) even an option? I haven’t tried it because it seems like a hell of a lot of work.

Any ideas?

PS: Maybe the stretch to constraint is the way out of all of this. Will give that a go.

I guess you could try the mesh deform modifier that’s in svn. I’m still trying to figure it out myself, but it’s basically a lattice deformation that can be anything, i.e. non-square.

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