Serban D. Porumbescu

Ph.D.
email: idav 'at' hiddenelephant.com
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Hello and welcome to my research page. My name is Serban (pronounced Sir-Bon) Porumbescu (pronounced Pour-oom-bess-coo). I completed my PhD in 2005. During my studies, my research was primarily focused on 2D surface parameterization and remeshing of large data. Some of my most interesting results involve 3D near surface parameterizations (see Shell Maps below). Ken Joy was my advisor.

After graduating in 2005, I spent some time at Sony R&D, NVIDIA, and my own little startup that focused on work in the nonprofit sector. In October 2008 I started a new company, Hidden Elephant, focused on iPhone application development.

I joined iPhone startup Tapulous in October of 2009 as a senior gameplay engineer. While there I worked on a number of different projects (two that come to mind: Tap Tap Radiation and Riddim Ribbon). That Fall I also designed and taught UCD's first iPhone development course with Ken Joy. I left Tapulous in September of 2010, two months after we were acquired by Disney, to focus on my own indie development projects.

In November 2010 my company, Hidden Elephant, partnered with Limbic Software. Together we developed the hit iOS game, Zombie Gunship (released July, 2011). I spent the rest of 2011 and big chuncks of 2012 adding features and updating Zombie Gunship.

I launched Lexmee, a puzzle word game, for iOS February 28th, 2013.

May 8th, 2014 Gunship X, a top down shooter for iOS, is released.

You can reach me via email at idav 'at' hiddenelephant.com.

Geometric Texturing Using Level Sets

Anders Brodersen, Ken Museth, Serban Porumbescu, Brian Budge
IEEE Transactions on Visualization and Computer Graphics 2008
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We present techniques for warping and blending (or subtracting) geometric textures onto surfaces represented by high resolution level sets. The geometric texture itself can be represented either explicitly as a polygonal mesh or implicitly as a level set. Unlike previous approaches, we can produce topologically connected surfaces with smooth blending and low distortion. Specifically, we offer two different solutions to the problem of adding fine-scale geometric detail to surfaces. Both solutions assume a level set representation of the base surface which is easily achieved by means of a mesh-to-level-set scan conversion. To facilitate our mapping, we parameterize the embedding space of the base level set surface using fast particle advection. We can then warp explicit texture meshes onto this surface at nearly interactive speeds or blend level set representations of the texture to produce high-quality surfaces with smooth transitions.

Download Geometric Texturing Using Level Sets

Shell Maps

Serban D. Porumbescu, Brian C. Budge, Louis Feng, Kenneth I. Joy
ACM SIGGRAPH 2005
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A shell map is a bijective mapping between shell space and texture space that can be used to generate small-scale features on surfaces using a variety of modeling techniques. The method is based upon the generation of an offset surface and the construction of a tetrahedral mesh that fills the space between the base surface and its offset.  By identifying a corresponding tetrahedral mesh in texture space, the shell map can be implemented through a straightforward barycentric-coordinate map between corresponding tetrahedra. The generality of shell maps allows texture space to contain geometric objects, procedural volume textures, scalar fields, or other shell-mapped objects. 

Download Shell Maps

Meshless Isosurface Generation from Multiblock Data

Christopher S. Co, Serban D. Porumbescu, Kenneth I. Joy
VisSym 2004
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We propose a meshless method for the extraction of high-quality continuous isosurfaces from volumetric data represented by multiple grids, also called multiblock data sets. Multiblock data sets are commonplace in computational mechanics applications. Relatively little research has been performed on contouring multiblock data sets, particularly when the grids overlap one another. Our algorithm proceeds in two steps. In the first step, we determine a continuous interpolant using a set of locally defined radial basis functions (RBFs) in conjunction with a partition of unity method to blend smoothly between these functions. In the second step, we extract isosurface geometry by sampling points on Marching Cubes triangles and projecting these point samples onto the isosurface defined by our interpolant. A surface splatting algorithm is employed for visualizing the resulting point set representing the isosurface. Because of our method's generality, it inherently solves the crack problem in isosurface generation. Results using a set of synthetic data sets and a discussion of practical considerations are presented. The importance of our method is that it can be applied to arbitrary grid data regardless of mesh layout or orientation.

Dataflow and Remapping for Wavelet Compression and View-dependent Optimization of Billion-Trangle Isosurfaces

Mark A. Duchaineau, Serban D. Porumbescu, Martin Bertram, Bernd Hamann, Kenneth I. Joy
in G. Farin, H. Hagen, and B. Hamann, eds., Approximation and Geometrical Methods for Scientific Visualization, Springer-Verlag, Heidelberg, Germany, 2003, 10 pages.
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Currently, large physics simulations produce 3D discretized field data whose individual isosurfaces, after conventional extraction processes, contain upwards of hundreds of millions of triangles. Detailed interactive viewing of these surfaces requires (a) powerful compression to minimize storage, and (b) fast view-dependent optimization of display triangulations to most efectively utilize high-performance graphics hardware. In this work, we introduce the first end-to-end multiresolution data flow strategy that can effectively combine the top performing subdivision-surface wavelet compression and view-dependent optimization methods, thus increasing efficiency by several orders of magnitude over conventional processing pipelines. In addition to the general development and analysis of the data flow, we present new algorithms at two steps in the pipeline that provide the "glue" that makes an integrated large-scale data visualization approach possible. A shrink-wrapping step converts highly detailed unstructured surfaces of arbitrary topology to the semi-structured meshes needed for wavelet compression. Remapping to triangle bintrees minimizes disturbing "pops" during realtime display-triangulation optimization and provides effective selective-transmission compression for out-of-core and remote access to extremely large surfaces. Overall, this is the first effort to exploit semi-structured surface representations for a complete large-data visualization pipeline.

Automatic Semi-Regular Mesh Construction from Adaptive Distance Fields

Peer Timo Bremer, Serban D. Porumbescu, Bernd Hamann, Kenneth I. Joy
Curve and Surface Fitting: Saint-Malo 2002
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This paper describes a method to construct semi-regular meshes for a surface S defined by the zero set of a trivariate function F(x,y,z), representing a distance field definition of S. An adaptive distance field (ADF) definition of S is obtained by constructing, adaptively, an octree decomposition of F's domain. The vertices of the octree-based definition of S lie either on the positive or negative side of S (or on S). Octree cells that are intersected by S are identified, and the faces of these cells that lie on the outside of S are projected onto S. The result is a quadrilateral mesh to which various procedures are applied that lead to an improved mesh containing a much smaller number of extraordinary vertices, i.e., non-valence-four vertices.

Virtual Clay Modeling Using Adaptive Distance Fields

Peer Timo Bremer, Serban D. Porumbescu, Falko Kuester, Bernd Hamann, Kenneth I. Joy, Kwan-Liu Ma
in H. R. Arambnia et al., eds., Proceedings of the 2002 International Conference on Imaging Science, Systems, and Technology (CISST 2002), Volume 1, Computer Science Research, Education, and Applications Press, Athens, Georgia, 2002.
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This paper describes an approach for the parametrization and modeling of objects represented by adaptive distance fields (ADFs). ADFs support the construction of powerful solid modeling tools. They can represent surfaces of arbitrary and even changing topology, while providing a more intuitive user interface than control-point based structures such as B-splines. Using the octree structure, an adaptively refined quadrilateral mesh is constructed that is topologically equivalent to the surface. The mesh is then projected onto the surface using multiple projection and smoothing steps. The resulting mesh serves as the ``interface'' for interactive modeling operations and high-quality rendering.

Interactive Display of Surfaces Using Subdivision Surfaces and Wavelets

Duchaineau, M.A., Bertram, M., Porumbescu, S., Hamann, B. and Joy, K.I.
in Kunii, T.L. ed., Proceedings of Spring Conference on Computer Graphics 2001, Comenius University, Bratislava, Slovak Republic, pp. 22--34.

Complex surfaces and solids are produced by large-scale modeling and simulation activities in a variety of disciplines. Productive interaction with these simulations requires that these surfaces or solids be viewable at interactive rates yet many of these surfaces/solids can contain hundreds of millions of polygons/polyhedra. Interactive display of these objects requires compression techniques to minimize storage, and fast view-dependent triangulation techniques to drive the graphics hardware. In this paper, we review recent advances in subdivision-surface wavelet compression and optimization that can be used to provide a framework for both compression and triangulation. These techniques can be used to produce suitable approximations of complex surfaces of arbitrary topology, and can be used to determine suitable triangulations for display. The techniques can be used in a variety of applications in computer graphics, computer animation and visualization.