[Bf-committers] IRC Meeting Minutes, 15 Aug, 2004

Ton Roosendaal bf-committers@blender.org
Thu, 19 Aug 2004 12:31:03 +0200


Great! That's three people already. :)
I am still recovering from LA jetlag and the busy period I've had the  
past month. My intention is to come with a structure proposal first,  
especially on the level how to integrate it within Blender nicely. That  
has it's limitations (and possibilities). For the real math & physics  
involved I'll need a lot of help from the experts then.

Let's do the initial discussion on this maillist then, and - if  
possible & required - try to make an appointment for a special irc  
session on the issues.


On Wednesday, Aug 18, 2004, at 12:30 Europe/Amsterdam, David  
Bourguignon wrote:

>> IRC Meeting Minutes, 15 Aug, 2004
>> 2) B-Con 1: possible 2.35 features & roadmap
>> * softbodies (Ton R/Jensen O.M.)
> Hi all,
> I missed last IRC meeting, but in a previous one, I said I was willing  
> to
> help with the softbodies. Since I have been very busy recently  
> (finding a
> job...) I haven't made any progress. According to last meeting  
> minutes, Ton
> and Jensen are in charge now, so I just want to give a recap of what I  
> was
> thinking about.
> I wrote roughly a year ago an overview of softbodies simulation in  
> computer
> graphics. It it is part of an heavy (~30 MB) pdf you will find here:
> http://perso.wanadoo.fr/david-m.bourguignon/pub/Bou03/
> However, I have put (temporarily) a relevant excerpt here:
> http://perso.wanadoo.fr/david-m.bourguignon/tmp/previous_work.pdf
> IMHO, there are two interesting approaches for softbodies in Blender.  
> In
> both cases, you need to transform your surface triangular mesh into a  
> volume
> tetrahedral mesh by (temporarily) inserting internal vertices. (Not an  
> easy
> problem if you want to obtain "nice" tetrahedra, but I think several  
> solutions are
> possible.)
> * First softbodies approach: discreet model.
> A paper on this method is available here:
> http://perso.wanadoo.fr/david-m.bourguignon/pub/BC00/
> - Pros: easy to code (extension of mass-spring systems), easy to  
> understand,
> easy to tinker with (IMHO, this is very important for artists).
> - Cons: rough approximation of the real physical behavior, eg, it is
> difficult to obtain quasi-incompressible behavior.
> I have to clean the code written for this paper, compile it under  
> linux and
> mswin to provide a nice demo. I think I can do this before the end of  
> next
> week.
> * Second softbodies approach: continuous model.
> IMHO, the most relevant paper is:
> G. Picinbono, H. Delingette, and N. Ayache. Non-Linear Anisotropic
> Elasticity for Real-Time Surgery Simulation. Graphical Models,
> 65(5):305-321, September 2003.
> You can find it here:
> ftp://ftp-sop.inria.fr/epidaure/Publications/Delingette/Picinbono- 
> GM03.pdf
> - Pros: classical continous mechanics equations solved in a very
> efficient way, thus the model is fast and accurate.
> - Cons: difficult to tinker with the model without a good continous
> mechanics background, and thus potentially difficult to use for  
> artists.
> That's all! Sorry for the long post. I welcome any question you may  
> have.
> David.
> -- 
> http://perso.wanadoo.fr/david-m.bourguignon/
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Ton Roosendaal  Blender Foundation ton@blender.org