I'm hoping to create my own simple character animation system and need
some guidance in joint deformation.  I'm looking for some
algorithms/conceptual explanations for deforming meshes around "joints"
in a bones animation style system.  A web search gives only leads to
sales of professional packages (and "Warez houses").  Anybody got some
leads on the following:

1) how to scale deformation as distance from joint increases
2) how to treat interpenetration of meshes
3) how to add gridding on expanding side of joint to preserve shape


I'm a FORTRAN programmer with nearly 20 years experience throwing
formulas around, so hairy math is no problem.  I'm also very "creative"
at crafting bizarre data structures within its limited repetoire.  In
short - not a newby, not afraid of heavy comp-sci stuff.  Just not
familiar with bending, deformable meshes.

Any help greatly appreciated.


tgl### [at] nettallycom

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You could try looking at the soure code at
http://www.darwin3d.com/gamedev.htm#gdm0598 for inspiration.

This looks like it does what you want (I haven't examined the code, only
compiled it to see if it works).

Andrew

Tim Glover wrote:
> 
> I'm hoping to create my own simple character animation system and need
> some guidance in joint deformation.  I'm looking for some
> algorithms/conceptual explanations for deforming meshes around "joints"
> in a bones animation style system.  A web search gives only leads to
> sales of professional packages (and "Warez houses").  Anybody got some
> leads on the following:
> 
> 1) how to scale deformation as distance from joint increases
> 2) how to treat interpenetration of meshes
> 3) how to add gridding on expanding side of joint to preserve shape
> 
> I'm a FORTRAN programmer with nearly 20 years experience throwing
> formulas around, so hairy math is no problem.  I'm also very "creative"
> at crafting bizarre data structures within its limited repetoire.  In
> short - not a newby, not afraid of heavy comp-sci stuff.  Just not
> familiar with bending, deformable meshes.
> 
> Any help greatly appreciated.
> 
> tgl### [at] nettallycom

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Tim Glover wrote:
> 
> I'm hoping to create my own simple character animation system and need
> some guidance in joint deformation.  I'm looking for some
> algorithms/conceptual explanations for deforming meshes around "joints"
> in a bones animation style system.  A web search gives only leads to
> sales of professional packages (and "Warez houses").  Anybody got some
> leads on the following:
> 
> 1) how to scale deformation as distance from joint increases
> 2) how to treat interpenetration of meshes
> 3) how to add gridding on expanding side of joint to preserve shape
> 
> I'm a FORTRAN programmer with nearly 20 years experience throwing
> formulas around, so hairy math is no problem.  I'm also very "creative"
> at crafting bizarre data structures within its limited repetoire.  In
> short - not a newby, not afraid of heavy comp-sci stuff.  Just not
> familiar with bending, deformable meshes.

You might want to try h-splines, possibly combined with Catmull-Clark
surfaces.  Check the Dragon Wing,
http://www.cs.ubc.ca/nest/imager/contributions/forsey/dragon/top.html. 
In particular check the page there on multiresolution surface
approximation http://www.cs.ubc.ca/spider/forsey/Approx/App_1.html. 
Also check out the paper by Hoppe, DeRose, et. al. in Tony DeRose's
recent papers at http://www.cs.washington.edu/homes/derose/papers.html. 
Finally, check out the Online Geometric Modelling Notes at
http://graphics.cs.ucdavis.edu/CAGDNotes/CAGD-Notes.html for a lot of
useful algorithms and general info.  In particular read the page on
Catmull-Clark surfaces at
http://graphics.cs.ucdavis.edu/CAGDNotes/Catmull-Clark/Catmull-Clark.html. 
Have fun.

Jerry Anning
cle### [at] dholcom

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Hmmm....  Looks interesting. Thanks!



Andrew Hedges wrote:
> 
> You could try looking at the soure code at
> http://www.darwin3d.com/gamedev.htm#gdm0598 for inspiration.
> 
> This looks like it does what you want (I haven't examined the code, only
> compiled it to see if it works).
> 
> Andrew
>

Post a reply to this message

Tim Glover wrote:

> I'm hoping to create my own simple character animation system and need
> some guidance in joint deformation.  I'm looking for some
> algorithms/conceptual explanations for deforming meshes around "joints"
> in a bones animation style system.  A web search gives only leads to
> sales of professional packages (and "Warez houses").  Anybody got some
> leads on the following:
>
> 1) how to scale deformation as distance from joint increases
> 2) how to treat interpenetration of meshes
> 3) how to add gridding on expanding side of joint to preserve shape
>
> I'm a FORTRAN programmer with nearly 20 years experience throwing
> formulas around, so hairy math is no problem.  I'm also very "creative"
> at crafting bizarre data structures within its limited repetoire.  In
> short - not a newby, not afraid of heavy comp-sci stuff.  Just not
> familiar with bending, deformable meshes.
>
> Any help greatly appreciated.
>
> tgl### [at] nettallycom

   There has been a new program written that you might want
to investigate. Developed by Warp, and currently is supported
by Chris Colefax, it is said to be able to dramatically reduce the
overall number of triangles used in a mesh object without any
noticeable loss of model resolution. It also has a built in feature
that will allow you to deform mesh objects in a variety of ways.
It may not feed your hunger for math but once you figure out
the kinematic actions you want to perform this utility may make
the road a little less rocky. There is a sister Pov macro file from
Chris that is supposed to work in harmony with Warps program.
I just haven't taken the time yet to figure out the relationship.

   You can find the programs available, for free, and ready for
download at the "Chris Colefax Incredible Include Files" web site.

http://www.geocities.com/SiliconValley/Lakes/1434/

Ken Tyler

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Although not very technical, this page has some ideas on things like
this:
http://freespace.virgin.net/hugo.elias/models/m_main.htm

Tim Glover wrote:
> 
> I'm hoping to create my own simple character animation system and need
> some guidance in joint deformation.  I'm looking for some
> algorithms/conceptual explanations for deforming meshes around "joints"
...

-- 
Chris Maryan
mailto:cma### [at] geocitiescom
***
Will work for cash.
***
Email me if you are interested in donating
to the Chris Maryan needs money fund.
We will also accept donations to the Chris
needs a Pentium II or SGI workstation 
fund and the Chris needs a car fund.

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As always, this newsgroup amazes me.  Great page. Thanks!

Tim G.


Chris Maryan wrote:
> 
> Although not very technical, this page has some ideas on things like
> this:
> http://freespace.virgin.net/hugo.elias/models/m_main.htm
> 
> 
> --
> Chris Maryan
> mailto:cma### [at] geocitiescom
> ***
> Will work for cash.
> ***
> Email me if you are interested in donating
> to the Chris Maryan needs money fund.
> We will also accept donations to the Chris
> needs a Pentium II or SGI workstation
> fund and the Chris needs a car fund.

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Came across these yesterday after leaving the message - --actually
looking for an old Rock.inc file!  Very interesting.  Looks like I'll
have some "thunking" to do! (thunking as in gee-wow thinking, not
thunking as in making a 32bit OS think it's 16 bit a la Windows!)


Thanks for the re-direct.

Tim G. 



Ken wrote:

> 
>    There has been a new program written that you might want
> to investigate. Developed by Warp, and currently is supported
> by Chris Colefax, it is said to be able to dramatically reduce the
> overall number of triangles used in a mesh object without any
> noticeable loss of model resolution. It also has a built in feature
> that will allow you to deform mesh objects in a variety of ways.
> It may not feed your hunger for math but once you figure out
> the kinematic actions you want to perform this utility may make
> the road a little less rocky. There is a sister Pov macro file from
> Chris that is supposed to work in harmony with Warps program.
> I just haven't taken the time yet to figure out the relationship.
> 
>    You can find the programs available, for free, and ready for
> download at the "Chris Colefax Incredible Include Files" web site.
> 
> http://www.geocities.com/SiliconValley/Lakes/1434/
> 
> Ken Tyler

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Tim Glover wrote:

> As always, this newsgroup amazes me.  Great page. Thanks!
>
> Tim G.

The address below will take you to a links page that has
several links to information on human modeling and human
motion studies. The first one I clicked on took me to a site
that contained information that was quite impressive.
The human animation links are about 1/6 th the way down
the page

http://atrey.karlin.mff.cuni.cz/~0rfelyus/bookmark.html

Ken Tyler

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