SpringLab

Interactive RT simulation of elastic bodies

Description

This program is a prototype of an interactive elastic model. It makes use of both spring and FEM forces, and several of the elasticity parameters can be modified in run-time (key bindings are displayed in the figure).
To use, left click and drag any point on any face of the model. When the mouse is released, new constraints can be added in the same way. To release such a constraint, right click on its face.

Play around with the parameters - the simulation (although using implicit time integration) can become unstable at certain parameters setup.

The model input format is a VOL file, the (ascii) simple output format of the freeware NetGen. Few sample models are included.

Usage:

SpringLab('sphere')
SpringLab('tissue_cut2')
SpringLab('stomach')
SpringLab('y')

REQUIRES ADDITIONAL FILES:
select3d by Joe Conti, and cameratoolbarnokeys by me.

• MATLAB release: MATLAB 7.2 (R2006a)
• Other requirements: cameratoolbarnokeys , select3d, preferrably some graphic hardware (would run very slow with software rendering).

[Anton Semechko]

Incredible! Many thanks for posting this!

[Tim Davis]

Very nice simulation, but I have a suggestion for improvment. There are some suspicious numerical techniques used here. See line 417 of Springlab.m, for example. You should never multiply by the inverse of a matrix. Using inv that way is inaccurate and very slow (althought it appears you're doing it only for matrices of modest size, so speed is not an issue). Anyway, "multiplying by the inverse" is what slash and backslash are for (they do not explicitly compute the inverse). This might be the source of instability that you've observed.

ForceCoeffMat=1/(dt*dt) *inv((U*W)*(Minv*U'));

[Jesse Parker]

Wow, this is really cool! Way more advanced than what I'm trying to do, but fun to play with.