Interactive skeleton-driven simulation: Difference between revisions

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{{short description|Scientific computer simulation technique}}

{{Orphan|date=April 2008}}

'''Interactive skeleton-driven simulation''' (or '''Interactive skeleton-driven dynamic deformations''') is a scientific [[computer simulation]] technique used to approximate realistic physical [[deformation (engineering)|deformation]]s of dynamic bodies in [[real-time computing|real-time]]. It involves using [[Elasticity (physics)|elastic]] [[dynamics (mechanics)|dynamics]] and [[optimization (mathematics)|mathematical optimization]]s to decide the body-shapes during motion and interaction with [[force]]s. It has various applications within realistic simulations for [[medicine]], 3D [[computer animation]] and [[virtual reality]].

'''Interactive skeleton-driven simulation''' (or '''Interactive skeleton-driven dynamic deformations''') is a scientific [[computer simulation]] technique used to approximate realistic physical [[deformation (engineering)|deformation]]s of dynamic bodies in [[real-time computing|real-time]]. It involves using [[Elasticity (physics)|elastic]] [[dynamics (mechanics)|dynamics]] and [[optimization (mathematics)|mathematical optimization]]s to decide the body-shapes during motion and interaction with [[force]]s. It has various applications within realistic simulations for [[medicine]], 3D [[computer animation]] and [[virtual reality]].

==Background==

Methods for simulating deformation, such as changes of shapes, of dynamic bodies involve intensive calculations, and several models have been developed. Some of these are known as [[''[[free-form deformation'']]'', ''skeleton-driven deformation'', ''dynamic deformation'' and ''anatomical modelling''. [[Skeletal animation]] is well known in [[computer animation]] and 3D character simulation. Because of the calculation intensitivityinsensitivity of the simulation, few interactive systems are available which realistically can simulate dynamic bodies in [[real-time computing|real-time]]. Being able to ''interact'' with such a [[Realism (arts)|realistic]] 3D model would mean that calculations would have to be performed within the constraints of a [[frame rate]] which would be acceptable via a [[user interface]].

Recent research has been able to build on previously developed models and methods to provide sufficiently efficient and realistic simulations. The promise for this technique can be as widespread as [[mimic]]ingking human [[facial expression]]s for [[face perception|perception]] of simulating a human actor in real-time or other [[cell (biology)|cell]] [[organism]]s. Using skeletal constraints and parameterized force to calculate deformations also has the benefit of matching how a single cell has a shaping [[skeleton]], as well as how a larger living organism might have an internal bone skeleton - such as the [[vertebrae]]s. The generalized external body force simulations makes [[Elasticity (physics)|elasticity]] calculations more efficient, and means real-time [[Human-computer interaction|interaction]]s are possible.

==Basic theory==

There are several components to such a simulation system:

* a [[polygon mesh]] defining the body shape of the model

* a coarse volumetric mesh using [[finite element method]]s to ensure complete integration over the model

* line constraints corresponding to internal skeleton and instrumented to the model

* [[linear]]izing of equations of motion to achieve interactive rates

* [[hierarchical]] regions of the mesh associated with skeletal lines

* blending of locally linearlized simulations

* a control lattice through [[Subdivision (graph theory)|subdivision]] fitting the model by surrounding and covering it

* a hierarchical basis containing functions which will provide values for deformation of each lattice

[[Domain of a function|___domain]] with calculations of these hierarchical functions similar to that of [[lazy evaluation|lazy]] [[wavelet]]s

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To achieve interactivity there are several optimizations necessary which are implementation specific.

Start by defining the object you wish to animate as a set (iei.e. define all the points):

<math>p : \Omega \times \mathbb{R} \rightarrow \mathbb{R}^3 : (x, t) \mapsto p(x, t)</math> .

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Let <math>p_S : S \times \mathbb{R} \rightarrow \mathbb{R}^3</math>

Then you need to define the rest state of the object (the non-wobble point):

<math>r(x) = \sum_{a} r_a \emptyset ^a (x) = r_a \emptyset ^a (x) = x</math>

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==See also==

* [[Kinematics]]

* [[Dynamics (mechanics)|Dynamics]]

* [[Computer animation]]

* [[Skeletal animation]]

* [[Morph target animation]]

* [[3D computer graphics]]

* [[Development of Spore]]

==References==

* ''[https://web.archive.org/web/20060902214406/http://grail.cs.washington.edu/theses/CapellPhd.pdf Interactive Character Animation Using Dynamic Elastic Simulation]'', 2004, Steve Capell Ph.D. dissertation.

* ''[https://web.archive.org/web/20060828072755/http://grail.cs.washington.edu/pub/papers/Capell-2002-ISD.pdf Interactive Skeleton-Driven Dynamic Deformations]'', 2002 [[SIGGRAPH]]. Authors: Steve Capell, Seth Green, Brian Curless, Tom Duchamp and Zoran Popović.

* ''[https://web.archive.org/web/20060828072336/http://grail.cs.washington.edu/pub/papers/Capell-2002-MFD.pdf A Multiresolution Framework for Dynamic Deformations]'', 2002 [[SIGGRAPH]].Authors: Steve Capell, Seth Green, Brian Curless, Tom Duchamp and Zoran Popović.

* ''[https://web.archive.org/web/20060828073725/http://grail.cs.washington.edu/pub/papers/Capell-2005-PBR.pdf Physically Based Rigging for Deformable Characters]'', 2005 [[SIGGRAPH]]. Authors: Steve Capell, Matthew Burkhart, Brian Curless, Tom Duchamp and Zoran Popović.

* ''[http://www.cs.unc.edu/~lin/COMP259-S05/LEC/24.ppt Skeleton-driven Deformation - lecture on physically-based modelling, simulation and animation]'', 2005, [[Ming C. Lin]], University of North Carolina, USA.

==External links==

* ''[http://grail.cs.washington.edu/projects/deformation/Capell-2002-ISD-divx.avi Video of aan interactive skeletal and model editor with introduction to the basic theory]'', University of Washington, USA.

* ''[http://grail.cs.washington.edu/projects/deformation/ Deformable Objects and Characters project]'', University of Washington, USA. Has example videos of the techniques.

* ''[http://grail.cs.washington.edu/projects/charanim/ Motion Libraries for Character Animation project]'', University of Washington, USA. Has example videos of the techniques.

{{DEFAULTSORT:Interactive Skeleton-Driven Simulation}}