How to pass a soft object through a narrow channel?

Question

I found an excelent Q/A about Some examples of shape key sculpting vs lattice?. @moonboots suggests in his answer to use a Lattice in order to deform an cylinder object:

How does that work? How can I pass a soft object through a narrow channel like @moonboots does in his answer?

Answer 1

What you've posted there is no soft object passing through a channel, it's actually a Cylinder with a Lattice Modifier moving through a Lattice object.

1. Add a Cylinder to your scene or whatever object you want to deform.
2. To be deformed smoothly it needs enough geometry, so subdivide it either in Edit Mode or with a Subdivision Surface modifier.
3. Add a Lattice to your scene (Shift+A > Lattice)
4. In the Lattice settings, set the Resolution W to at least 3.
5. Go to Edit Mode and scale the middle vertices down so that they narrow the Lattice in the center.
6. Add a Lattice Modifier to the Cylinder and under Object choose the Lattice.
7. Now you can move the Cylinder up and down and it gets deformed.

EDIT: I'm too slow. The above solution is correct, this is just a shorter version.

Answer 2

This can be achieved using the Lattice deform modifier.

1. Create a Lattice object (ShiftA, Lattice). In the properties tab, set the U, V and W resolution to a sufficiently high number (I used 5).

2. In Edit mode (Tab), select the middle layer of points in the lattice (C to enter paint selection mode, then paint, then Enter). Scale them down (S) to define the deformation the Lattice should have.

3. Add the Lattice modifier to the object you wish to deform, and select the Lattice object you created. Note: you need to ensure that your object has enough vertices for a smooth transformation. If it is too low-resolution, you can add a subdivision surface modifier to increase it.

Your object should now be deformed by the lattice. As you move it through the lattice in object mode, it will appear to squeeze through the narrow region.

Answer 3

Another way is to use simulation. A cloth simulation using pressure behaves a lot like a soft body and can illustrate the effect you want to show.

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Details

1. Create the geometry for the channel and the object to pass through.
2. On the physics panel for the channel, add collision physics.
3. On the physics panel for the object, add soft cloth physics. Settings shown below:

4. Animate!

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Example Blender 2.92 file -