

Welcome 
Thanks for visiting my web site. I graduated from UC Davis with computer
science degree, worked for few years developing software for Adobe Illustrator
(detail here), and am now back for graduate studies.
My academic interests revolve around computer graphics. 
Research 

Research Interest 
Developing new algorithms and data structures for efficient processing
of geometric shapes. A major goal of this research is to guarantee desired
surface properties such as geometric accuracy or topological properties
such as being a manifold. An application involves interactive shape modeling
and sculpting in virtual environments.





Publications 

Dissertation 
Dissertation




GPUassisted
Surface Reconstruction on Locallyuniform Samples [pdf]
Yong J Kil and Nina Amenta,
Proceedings of International Meshing Roundtable, 2008.
Abstract:
In pointbased graphics, surfaces are represented by point clouds without
explicit connectivity. If the distribution of the points can be carefully
controlled, surface reconstruction becomes a much easier problem. We present
a simple, completely local surface reconstruction algorithm for input
point distributions that are locally uniform. The locality of the computation
lets us handle large point sets using parallel and outofcore methods.
The algorithm can be implemented robustly with floatingpoint arithmetic.
We demonstrate the simplicity, efficiency, and numerical stability of
our algorithm with an outofcore and parallel implementation using graphics
hardware.




Laser Scanner Superresolution
Yong Joo Kil, Boris Mederos, and Nina Amenta
Eurographics Symposium on Pointbased Graphics 2006.
Combining
Laser Scans
Yong Joo Kil, Boris Mederos, and Nina Amenta
Sketch of ACM SIGGRAPH 2006.
Abstract:
We give a method for improving the resolution of surfaces captured with
a laser range scanner by combining many very similar scans. This idea
is an application of the 2D image processing technique known as superresolution.
The input lowerresolution scans are each randomly shifted, so that each
one contributes slightly different information to the final model. Noise
is reduced by averaging the input scans.




Evolutionary
Morphing [movie]
David F. Wiley, Nina Amenta, Dan A. Alcantara, Deboshmita Ghosh,
Yong J Kil,
Eric Delson, Will HarcourtSmith, F. James Rohlf, Katherine St. John,
Bernd Hamann
Proceedings of IEEE Visualization 2005
[More Info].
Abstract:
We introduce a technique to visualize the gradual evolutionary change
of the shapes of living things as a morph between known threedimensional
shapes. Given geometric computer models of anatomical shapes for some
collection of specimens  here the skulls of the some of the extant members
of a family of monkeys  an evolutionary tree for the group implies a
hypothesis about the way in which the shape changed through time. We use
a statistical method which expresses the value of some variable  in this
case the shape  at an internal point in the tree as a weighted average
of the values at the leaves. The framework of geometric morphometrics
can then be used to define a shapespace, based on the correspondences
of landmark points on the surfaces, within which these weighted averages
can be realized as actual surfaces. Our software provides tools for performing
and visualizing such an analysis in three dimensions. Beginning with laser
range surfaces scans of skulls, we use our landmark editor to interactively
place landmark points on the surface. We use these to compute a treemorph
which smoothly interpolates the shapes across the tree. Each intermediate
shape in the morph is a linear combination of all of the input surfaces.
We create a surface model for an intermediate shape by warping all the
input meshes towards the correct shape and then merging them together.
Our merging procedure is novel. Given several similar surface meshes,
we compute a weighted average between them by averaging their associated
trivariate squared distance functions, and then extract the extremal surface
which traces out the "valleys" along which the averaged function
is nearly zero.




3D Warp Brush Modeling
Y. Kil, P. Renzulli, O. Kreylos, B. Hamann, G. Monno, O.G. Staadt.
Journal of Computer and Graphics, ELSEVIER, Vol. 30, No. 4, 2006.
3D Warp Brush: Interactive FreeForm
Modeling on the Responsive Workbench
Y. Kil, P. Renzulli, O. Kreylos, B. Hamann, G. Monno, O.G. Staadt
Proceedings of IEEE Virtual Reality 2005.
Abstract:
We introduce the 3D warp brush, a method for interactive shape modeling
in a immersive virtual reality environment. 3D warp brushes are implicitlydefined
tools that operate on triangle meshes. We combine the efficiency of explicit
mesh representations with implicit modeling operators. The area of influence
of a 3D warp brush can be of arbitrary shape since it has an associated
distance field. We define different warp functions including drag, explode,
and whittle. A unique feature of our framework is the ability to convert
meshes into 3D warp brushes at run time. The use of a Responsive Workbench
and twohanded interaction allows the user to exploit the full potential
of the modeling system by intuitive and easy modification of a base surface
into a desired shape. We present models, which have been created and modified
using 3D warp brushes, to demonstrate the usefulness of our framework.




Defining Point Set Surfaces
Nina Amenta and Yong Joo Kil
Journal of ACM SIGGRAPH, pp. 264270,
2004.
[More Info].
Abstract:
The MLS surface, used for modeling and rendering with point clouds, was
originally defined algorithmically as the output of a particular meshless
construction. We give a new explicit definition in terms of the critical
points of an energy function on lines determined by a vector field. This
definition reveals connections to research in computer vision and computational
topology. Variants of the MLS surface can be created by varying the vector
field and the energy function. As an example of such a generalization,
we define a pointset surface for surfels (points equipped with normals).
We also make an important technical observation: the procedures described
in the literature to take points in space onto the MLS surface do not,
in fact, produce points of the MLS surface. We describe a simple iterative
procedure which does, for any of the variants.




The Domain of a Point Set Surface
Nina Amenta and Yong Joo Kil
Eurographics Symposium on Pointbased
Graphics, pp. 139147, 2004.
[More Info].
Abstract:
It is useful to be able to define a twodimensional pointset surface
determined by a point cloud. One popular definition is Levin's MLS surface.
This surface is defined on a domain which is a threedimensional, a narrow
region around the input point cloud. If we were to extend the definition
outside the domain, we would produce components of the surface which are
far from the point cloud. This is important in practice, since when moving
points onto the MLS surface, we need to begin with an initial guess which
is within the domain. We visualize the domain in two dimensions, and explain
why it is so narrow. We also consider two MLS variants which can be defined
on a wider domain without producing spurious surface components. One is
efficient and works well except near sharp corners. The other is computationally
expensive but seems to work well everywhere.


Resume 
Here's my cv.
Here's my visual resume.
. 
Talk to me! 
I do enjoy a nice conversation. You can contact
me:
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Personal 
Here is link to my personal information.
My new website justfoc.us. .links

Last modified Nov 2007 