Budirijanto Purnomo (Budi Purnomo)

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Hi, I do not maintain this website anymore, please visit my new website here. In 2008, I graduated from Johns Hopkins University with a Computer Science Ph.D. degree. I am currently working as a Senior Software Engineer in the 3D Application Research Group of Advanced Micro Devices, Marlborough, MA.
In Summer 2006, I was a technical scholar in the Center for Applied Scientific Computing at Lawrence Livermore National Laboratory. In Summer 2004, I was a Graphics Software Engineer Intern at Pixar Animation Studios.

As a member of JHU Computer Graphics Group, I am working closely with Dr. Subodh Kumar and Dr. Jonathan Cohen. Recent projects:

	Multi-grained Level of Detail Using a Hierarchical Seamless Texture Atlas -- SIGGRAPH Symposium on Interactive 3D Graphics and Games 2007 Collaborators: Krzysztof Niski and Dr. Jonathan Cohen. Previous algorithms for view-dependent level of detail provide local mesh refinements either at the finest granularity or at a fixed, coarse granularity. The former provides triangle-level adaptation, often at the expense of heavy CPU usage and low triangle rendering throughput; the latter improves CPU usage and rendering throughput by operating on groups of triangles. We present a new multiresolution hierarchy and associated algorithms that provide adaptive granularity. This multi-grained hierarchy allows independent control of the number of hierarchy nodes processed on the CPU and the number of triangles to be rendered on the GPU. We employ a seamless texture atlas style of geometry image as a GPU-friendly data organization, enabling efficient rendering and GPU-based stitching of patch borders. We demonstrate our approach on both large triangle meshes and terrains with up to billions of vertices. Video (56 MB, H.264 codec, Quicktime 7).
	Digital Hammurabi: Design and Development of a 3D Scanner for Cuneiform Tablets -- IS&T SPIE Electronic Imaging 2006 Collaborators: Daniel Hahn (JHU APL), Dr. Kevin C. Baldwin (JHU APL), Dr. Donald Duncan (JHU APL) and Dr. Jonathan Cohen. We describe a 3D scanner capable of acquiring the shape, color, and reflectance of a tablet as a complete 3D object. This data set could then be stored in an online library and manipulated by suitable rendering software that would allow a user to speficy any view direction and lighting condition. The scanner utilizes a camera and telecentric lens to acquire images of the tablet under varying controlled illumination conditions. Image data are processed using photometric stereo and structured light techniques to determine the tablet shape; color information is reconstructed from primary color monochrome image data. The scanned surface is sampled at 26.8 micron lateral spacing and the height information is calculated on a much smaller scale. Scans of adjacent tablet sides are registered together to form a 3D surface model.
	Hardware-Compatible Vertex Compression Using Quantization and Simplification -- SIGGRAPH/Eurographics Symposium on Graphics Hardware 2005 Collaborators: Jonathan Bilodeau, Dr. Jonathan Cohen, and Dr. Subodh Kumar. We present a vertex compression technique suitable for efficient decompression on graphics hardware. Given a user-specified number of bits per vertex, we automatically allocate bits to vertex attributes for quantization to maximize quality, guided by an image-space error metric. This allocation accounts for the contraints of graphics hardware by packing the quantized attributes into bins associated with the hardware's vectorized vertex data elements. We show that this general approach is also applicable if the user specifies a total desired model size. We present an algorithm that integrally combines vertex decimation and attribute quantization to produce the best quality model for a user-specified data size. Such models have an appropriate balance between the number of vertices and the number of bits per vertex. Vertex data is transmitted to and optionally stored in video memory in the compressed form. The vertices are decompressed on the fly using a vertex program at rendering time. Our algorithm not only work well within the constraints of current graphics hardware but also generalize to a setting where these constraints are relaxed. They apply to models with a wide variety of vertex attributes, providing new tools for optimizing space and bandwidth constraints of interactive graphics applications.
	Digital Hammurabi Project: Digitizing Cuneiform Tablets -- VAST 2004 Collaborators: Yuan Chen, Jonathan Bilodeau, John Graetingger, Dr. Jonathan Cohen, Dr. Subodh Kumar, Dean Snyder, Dr. Jerrold Cooper (Near Eastern Studies), Daniel Hahn (JHU APL) and Dr. Donald Duncan (JHU APL). Advances in digital technology for the graphic and textual representation of manuscripts have not, until recently, been applied to the world's oldest manuscripts, cuneiform tablets. This is due in large part both to the three-dimensional nature of cuneiform tablets and to the complexity of the cuneiform script system. The Digital Hammurabi Project and the Initiative for Cuneiform Encoding announce success in encoding Sumero-Akkadian cuneiform in Unicode while also demonstrating advances in 3-D scanning and visualization of cuneiform tablets, showcased by iClay, a cross-platform, Internet-deployable, Java applet that allows for the viewing and manipulation of 2D+ images of cuneiform tablets.
	Seamless Texture Atlases -- SIGGRAPH/Eurographics SGP 2004 Collaborators: Dr. Jonathan Cohen and Dr. Subodh Kumar. Texture atlas parameterization provides an effective way to map a variety of color and data attributes from 2D texture domains onto polygonal surface meshes. However, the individual charts of such atlases are typically plagued by noticeable seams. We describe a new type of atlas which is seamless by construction. Our seamless atlas comprises all quadrilateral charts, and permits seamless texturing, as well as per-fragment down-sampling. We demonstrate the use of this atlas for capturing appearance attributes and producing seamless rendering.
	A System for Unwrapping and Visualizing Cuneiform Tablets -- JHU Magazine September 2003 Collaborators: Dr. Jonathan Cohen and Dr. Subodh Kumar. We present an automatic system for unwrapping (flattening) 3-D scanned cuneiform tablets. It uses a new out-of-core clustering, low distortion parameterization and non-photorealistic rendering. We can also capture attributes (colors or normals) into textures for efficient rendering. This work as a part of Digital Hammurabi project appeared as the cover story of the September 2003 issue of Johns Hopkins magazine. It was also demonstrated to the participants of Initiative for Cuneiform Encoding (an international group of cuneiformists, unicode experts, linguists and font architects) in Baltimore on June 2003.
	High-Fidelity Walkthroughs of Large Virtual Environments -- IEEE TVCG, Vol. 11, No. 1, Jan/Feb 2005 Collaborators: Jatin Chhugani, Dr. Shankar Krishnan (AT&T Research), Dr. Suresh Venkatasubramanian (AT&T Research), Dr. David Johnson (AT&T Research), Dr. Jonathan Cohen, and Dr. Subodh Kumar. We combine two rendering acceleration techniques (LOD and visibility) into one common framework. We show that time and storage requirements are not prohibitive for large models when we shift all these computations into a pre-computation phase. By using one pixel of screen space error (LOD), we are able to show high-fidelity images and still be able to maintain interactive rates throughout walkthrough of UNC Power plant's model (13 million triangles).
	General From-Region Visibility for Large Models Collaborators: Jatin Chhugani, Dr. Shankar Krishnan (AT&T Research), Dr. Jonathan Cohen, and Dr. Subodh Kumar. We present an efficient hardware-accelerated algorithm for region-based visibility computation for large models. The algorithm works for general and out-of-core scenes. It conservatively bounds shadow-volumes and reduces the general shadow containment problem to hardware occlusion queries. A video describing this algorithm: quicktime (5 MB).

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