Semi rigid body simulation: Opinions and suggestions - Java-Games

>I am trying to simulate a catether for a medical simulation project. I
>believe that i can reach a good degree of realism with a multirigid
>body in which each body is connected to the other with an elastic
>sperical joint. I am thinking of modelling this in ODE (open dynamics
>engine) using a set of bodies connected with Ball and Socket joints
>and adding elastic forces near the anchor of each joint. Do u think
>this approach is suitable??
>
>Thanks in advance
>Regards
>
>Luca
>

Ewww, yucky ;-)

I haven't used ODE, but have heard a lot about it. That might work fine, but
depending on what you're interested in there might be easier ways. I'm not
sure how stable ODE is with multiple bodies attached this way, or even if it's
possible. Can you elaborate on what you're looking for in this project?


Todd Wasson
Racing Software
http://PerformanceSimulations.com
http://performancesimulations.com/scnshot4.htm

"ciao" <swengineerit@yahoo.it> wrote in message
news:d93cc25b.0401160108.3ab13a3a@posting.google.com...
> I am trying to simulate a catether for a medical simulation project. I
> believe that i can reach a good degree of realism with a multirigid
> body in which each body is connected to the other with an elastic
> sperical joint. I am thinking of modelling this in ODE (open dynamics
> engine) using a set of bodies connected with Ball and Socket joints
> and adding elastic forces near the anchor of each joint. Do u think
> this approach is suitable??

My opinion is to look at the problem differently. The
"physics" of the situation is to make sure the tip of the
catheter can follow a path approximately in the center
of the tube-shaped vessel into which it is inserted. If
the tip has a path it can follow through the vessel, the
rest of the catheter must follow the tip. Assuming that
the catheter is itself a tube surface with a constant
radius R, the problem reduces to computing distance
D from the tip to the vessel boundary. If R < D, the
tip can move a small step in the direction tangential
to the central curve of the vessel tube surface. Over
time the tip has moved along a (polyline) path that is
used as the central curve for drawing the catheter as
a tube surface.

--
Dave Eberly
eberly@magic-software.com
http://www.magic-software.com
http://www.wild-magic.com

Ur suggestion is smart, and certainly merit consideration. However the
system has an haptic interface and it should be able to reproduce
situations that arise when the catether is driven badly. I have seen
that u are the author of a very good book on physic simulation ( which
i am going to buy aniway ) so i believe u are the right person to ask
this question:

how to add stifness and damping at the joints??

Regards
Luca

"Dave Eberly" <eberly@magic-software.com> wrote in message news:<zJSNb.9788$q4.3898@newsread3.news.atl.earthlink.net>...
> "ciao" <swengineerit@yahoo.it> wrote in message
> news:d93cc25b.0401160108.3ab13a3a@posting.google.com...
> > I am trying to simulate a catether for a medical simulation project. I
> > believe that i can reach a good degree of realism with a multirigid
> > body in which each body is connected to the other with an elastic
> > sperical joint. I am thinking of modelling this in ODE (open dynamics
> > engine) using a set of bodies connected with Ball and Socket joints
> > and adding elastic forces near the anchor of each joint. Do u think
> > this approach is suitable??
>
> My opinion is to look at the problem differently. The
> "physics" of the situation is to make sure the tip of the
> catheter can follow a path approximately in the center
> of the tube-shaped vessel into which it is inserted. If
> the tip has a path it can follow through the vessel, the
> rest of the catheter must follow the tip. Assuming that
> the catheter is itself a tube surface with a constant
> radius R, the problem reduces to computing distance
> D from the tip to the vessel boundary. If R < D, the
> tip can move a small step in the direction tangential
> to the central curve of the vessel tube surface. Over
> time the tip has moved along a (polyline) path that is
> used as the central curve for drawing the catheter as
> a tube surface.

I've bought 3d game engine design and game physic. Compliments, superb quality!
There's no need for other books on realt time physic.

I'm just using ur code in the medical simulation system we are developing.

Greets


swengineerit@yahoo.it (ciao) wrote in message news:<d93cc25b.0401161359.47261d3b@posting.google.com>...
> Ur suggestion is smart, and certainly merit consideration. However the
> system has an haptic interface and it should be able to reproduce
> situations that arise when the catether is driven badly. I have seen
> that u are the author of a very good book on physic simulation ( which
> i am going to buy aniway ) so i believe u are the right person to ask
> this question:
>
> how to add stifness and damping at the joints??
>
> Regards
> Luca
>
> "Dave Eberly" <eberly@magic-software.com> wrote in message news:<zJSNb.9788$q4.3898@newsread3.news.atl.earthlink.net>...
> > "ciao" <swengineerit@yahoo.it> wrote in message
> > news:d93cc25b.0401160108.3ab13a3a@posting.google.com...
> > > I am trying to simulate a catether for a medical simulation project. I
> > > believe that i can reach a good degree of realism with a multirigid
> > > body in which each body is connected to the other with an elastic
> > > sperical joint. I am thinking of modelling this in ODE (open dynamics
> > > engine) using a set of bodies connected with Ball and Socket joints
> > > and adding elastic forces near the anchor of each joint. Do u think
> > > this approach is suitable??
> >
> > My opinion is to look at the problem differently. The
> > "physics" of the situation is to make sure the tip of the
> > catheter can follow a path approximately in the center
> > of the tube-shaped vessel into which it is inserted. If
> > the tip has a path it can follow through the vessel, the
> > rest of the catheter must follow the tip. Assuming that
> > the catheter is itself a tube surface with a constant
> > radius R, the problem reduces to computing distance
> > D from the tip to the vessel boundary. If R < D, the
> > tip can move a small step in the direction tangential
> > to the central curve of the vessel tube surface. Over
> > time the tip has moved along a (polyline) path that is
> > used as the central curve for drawing the catheter as
> > a tube surface.

Am i wrong or your book doesnt discuss how to force constraints like
links or joints??

Cheers
Luca


swengineerit@yahoo.it (ciao) wrote in message news:<d93cc25b.0402100626.2819ecb1@posting.google.com>...
> I've bought 3d game engine design and game physic. Compliments, superb quality!
> There's no need for other books on realt time physic.
>
> I'm just using ur code in the medical simulation system we are developing.
>
> Greets
>
>
> swengineerit@yahoo.it (ciao) wrote in message news:<d93cc25b.0401161359.47261d3b@posting.google.com>...
> > Ur suggestion is smart, and certainly merit consideration. However the
> > system has an haptic interface and it should be able to reproduce
> > situations that arise when the catether is driven badly. I have seen
> > that u are the author of a very good book on physic simulation ( which
> > i am going to buy aniway ) so i believe u are the right person to ask
> > this question:
> >
> > how to add stifness and damping at the joints??
> >
> > Regards
> > Luca
> >
> > "Dave Eberly" <eberly@magic-software.com> wrote in message news:<zJSNb.9788$q4.3898@newsread3.news.atl.earthlink.net>...
> > > "ciao" <swengineerit@yahoo.it> wrote in message
> > > news:d93cc25b.0401160108.3ab13a3a@posting.google.com...
> > > > I am trying to simulate a catether for a medical simulation project. I
> > > > believe that i can reach a good degree of realism with a multirigid
> > > > body in which each body is connected to the other with an elastic
> > > > sperical joint. I am thinking of modelling this in ODE (open dynamics
> > > > engine) using a set of bodies connected with Ball and Socket joints
> > > > and adding elastic forces near the anchor of each joint. Do u think
> > > > this approach is suitable??
> > >
> > > My opinion is to look at the problem differently. The
> > > "physics" of the situation is to make sure the tip of the
> > > catheter can follow a path approximately in the center
> > > of the tube-shaped vessel into which it is inserted. If
> > > the tip has a path it can follow through the vessel, the
> > > rest of the catheter must follow the tip. Assuming that
> > > the catheter is itself a tube surface with a constant
> > > radius R, the problem reduces to computing distance
> > > D from the tip to the vessel boundary. If R < D, the
> > > tip can move a small step in the direction tangential
> > > to the central curve of the vessel tube surface. Over
> > > time the tip has moved along a (polyline) path that is
> > > used as the central curve for drawing the catheter as
> > > a tube surface.

"ciao" <swengineerit@yahoo.it> wrote in message
news:d93cc25b.0402111236.5557b6cb@posting.google.com...
> Am i wrong or your book doesnt discuss how to force constraints like
> links or joints??

Both the material on Lagragian dynamics and mass-spring
systems cover such topics.

I think a better medium for your questions about the
book is to send email to me directly.

--
Dave Eberly
eberly@magic-software.com
http://www.magic-software.com
http://www.wild-magic.com