FEM/PBD topology change

Hello,first thanks for your contributions in imstk.

I want to realize the topology change of FEM or PBD 3D model. I know that PBDPickingExample demonstrates the topology change of 2D pbd model, but further I want to interact with a 3D model and change its topology.

I noticed that kitawre published an article based on iMSTK in 2019. “Towards an Advanced Virtual Ultrasound-guided Renal Biopsy Trainer”.@sreekanth.arikatla You are one of the authors.
And I saw the product effect demonstration of this article on the imstk website, I cut a picture in which the puncture deformation of the kidney is what I want to achieve, but there is no collisionhandling related to the 3D model in imstk. Does this means The related implementation of this part is temporarily not open source? Or does it require some other efforts? Hope to get some advices.

Medical simulation cannot be done without tissue deformation.:rofl:

Hi, I can only comment on PBD right now.

PBDPickingExample does not do cutting yet. We are working on it for another project right now. We do have a couple of prototypes that do it.

As of right now you can swap the topology of a geometry and reinitialize a model (done in PBDClothRemap example). But, for example, if you were using PBD with distance constraints and reinit’d you would end up with new resting lengths (similar issues with other constraints and even with FEM). You can certainly insert/remove PBD constraints yourself but it is not yet handled for you.

In addition to what Andrew stated, I just want to say that in the example of the renal biopsy you posted, what you see is a needle-tissue interaction implemented using linear projection constraints (LPC; which make sure that once the nodes fall on the needle they are kinematically constrained to only move along the needle). This example does not show topology changes.

LPCs are implemented in imstk (see this) which can be handled by the modified Conjugate Gradient solver.

Do let us know if you LPC would work for your application and we can provide more guidance including literature references.

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