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I have the feeling i'm on the wrong way to do this. Because its part of the mesh. So, maybe somebody know it. How can i add movement to the tentacles in the wind? Like Hair. Sadly the whole mesh move with the wind, but i only want the tentacles.

enter image description here

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    $\begingroup$ have you tried with Cloth Physics? $\endgroup$ – moonboots Jul 24 at 18:18
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    $\begingroup$ Add softbody or cloth physics, or do it the hardway by adding bones and weight painting $\endgroup$ – Retrax Jul 24 at 18:25
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You can achieve this by using a Soft Body Lattice to automatically deform your mesh and react to the physics. The advantage of this over making the whole mesh a Soft Body is that each tendril can be given its own soft body settings (so some could be stiffer or heavier than others) and also your actual mesh geometry will not affect the simulation (making it simpler and quicker to simulate without having to change the geometry of your mesh).

To start, create a Lattice object and increase 'U' to give it enough detail in that direction. Scale it and position it over your 'tendril'. After re-scaling, ensure you 'Apply Scale' to ensure the simulation is consistent.

create lattice, scale and position

If you need to you can reposition each vertex of the lattice in Edit mode so that it evenly surrounds your mesh (in my case I used a straight extrusion for simplicity).

Anchor the 'base' of the lattice by adding a new Vertex Group (we'll call it 'Anchor') and assigning the 'base' vertices to that group.

assign the 'anchor'

Similarly, on your mesh, create a new Vertex Group (in my case named 'Tendril') and in Edit mode assign all vertices in the tendril to that group.

assign mesh vertices to the group

Select the lattice, hold Shift and select the mesh, press Ctrl+P and parent the lattice to the mesh so that it follows it.

parent lattice to the mesh

Select the lattice and add Soft Body physics. In the Goal, set the Anchor as the Vertex Group, increase Stiffness to 0.999 and Default Strength to 1.0. Set the rest of the soft body settings as desired. For me I set the Object Mass as 0.1kg, set the Edge Springs to 0.8 Pull and Push and Bending to 2 and enabled Stiffness.

soft body settings

Select the mesh, add a Lattice deform modifier and set the Target to the lattice, with the Vertex Group set to Tendril.

modifier

Now run the simulation and you should have the tendril reacting to the soft body physics.

animated result

The mesh should now respond to forces and movement. For multiple tendrils, simply repeat the process - adding more soft body lattices and further groups and modifiers for each tendril.

Blend file included

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    $\begingroup$ Nice, because it can be applied to an existing mesh relatively easily. I made some progress having bones follow a weighted-pin single-strand cloth simulation, but had to chuck it because of collision detection. Can soft-bodies be set up / use proxies in some way to avoid themselves / one another by some margin? Maybe this is a question I should post myself. $\endgroup$ – Robin Betts Jul 25 at 10:22
  • $\begingroup$ Thanks! The soft body can collide with meshes so you can to collision - but you do have to be careful that it isn’t set to collide with its own mesh - so would need a proxy so that you can control the collision collection. It should work to have another (hidden) collision mesh Also controlled by the same lattice and use that to collide with all the lattices controlling the other tendrils. This is similar to another question I was already working on (so I Had a bit of a head start with this one!). $\endgroup$ – Rich Sedman Jul 25 at 10:40
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It might be doable with only Cloth Physics but I don't know it enough to find the settings that would prevent face collisions, so here is a method that works:

  • Create a vertical plane with for example 5 different faces, assign it a series of vertex groups, the 2 bottom vertices will be group1, then the group above will be group2 and so on. Also create a new group that will be the Pinning group: in Weight Paint mode paint a gradient that goes from red on the top to blue on the bottom. Give this plane a Cloth physics and in the Shape > Pin Group select the ^pinning group you've created.

  • Create 5 bones that follow the vertical plane, with the head at the position of each plane's group. Deparent each bone. Give each bone a Bone Constraint > Child Of, for the bottom one choose group1 as Vertex Group, and so on. Each time press on the constraint Set Inverse button so that the bones stay in place.

  • Parent the tentacle mesh to the bones With Automatic Weight.

  • Create a Force Field > Wind to test the rigging.

enter image description here

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