Keeping the shape?

My model has long arms the shape of a tube. When I move them, how do I keep the round shape of these tubes without having to move single vertexes?

I presume you’ve used an armature to rig the arms?

If so, make sure that each intersection has a significant weight overlap (vertex weight groups).

An alternative would be to use a lattice and parent the lattice itself to the armature (so that manipulating the armature affects the lattice which smoothly bends the mesh).

Does this help?

Thanks for replying. I’m not going to animate but I want to move the model to different positions and then render hi-resolution images so I guess I have to study rigging and skinning.

Just use a lattice. When you’re done with it, apply the deformation and delete. No rigging necessary.

Good luck!

How would you apply a lattice to part of a model, like one arm? Is it just a question of positioning it.

Yep, like sticking the arm in a PVC pipe.