Thanks Ben. That is some good info. I was thinking more along implementing the Harmonic Coordinates approach. I think Pixar had some papers on it.
Sent from my iPhone > On Dec 11, 2013, at 10:50 PM, Ben Houston <[email protected]> wrote: > > My knowledge is out of date, but off the top of my head.... > > Cage deformers are often written using a cubic interpolant rather than affine > ones. If you use a grid cage you can use Bezier Volumes, which are just a > generalization of https://en.wikipedia.org/wiki/B%C3%A9zier_surface. If you > are using a regular grid, you can just take 3D coordinates relative to each > grid. If you use a tetrahedral mesh, you can use generalization of the Cubic > Triangle for deformation: https://en.wikipedia.org/wiki/B%C3%A9zier_triangle > and then you need to use barycentric coordinates to get a relative spatial > relationship. > > So I think yes, barycentric coordinates within a space filling discretization > of space, either a grid or a tetrahedralization with a cubic interpolate as > you start to deform them. > > I implemented the grid-based deformation with cubic volumes and got this > result: > > http://www.exocortex.org/ben_software/hd-ffd.zip > > I have also implemented the tetrahedral-based discretization with Christopher > Batty to deform a high resolution object to follow the path of a low > resolution object to really good success. The only issue is that tetrahedral > meshes suck to create and maintain efficiently. It is the bunny getting > crushed in the gears at the end of this video -- the actual simulation bunny > was super low res, but we uprezed it for rendering: http://vimeo.com/874168 > > Best regards, > -ben > > > >> On Wed, Dec 11, 2013 at 5:09 PM, Alok Gandhi <[email protected]> >> wrote: >> Hi All, >> >> Very soon, I am starting on my own generic custom cage deformer. A mix of >> C++/Cython/Python. >> >> I am thinking of implementing fast calculations on barycentric coordinates >> with affine transformations. I have some good papers (in my treasure trove >> but haven't checked it yet). >> >> Anyone suggest a different approach other than barycentring coordinates. >> >> The reason I will be writing this is for (proof of concept / prototype for >> now) is to be able to get point cache data from a low res geometry and then >> use this outside of an DCC to convert to high res deformations. >> >> This ways existing animation pipelines which have to rely on switching to >> higher resolutions before caching out do not have to do so. Simply export >> out point caches (alembic, pc2, mdd, bgeo, icecache etc.) and then apply >> this to a high res point data outside of any DCC as post process, even on >> farms from command line for example. >> >> -- >> > > > > -- > Best regards, > Ben Houston > Voice: 613-762-4113 Skype: ben.exocortex Twitter: @exocortexcom > http://Clara.io - Professional-Grade WebGL-based 3D Content Creation
