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Stippling and Silhouette Rendering on Geometry Image Space
X. Yuan, M. X. Nguyen, N. Zhang, and B. Chen.
Eurographics Symposium on Rendering 2005.
Abstract:
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Volume Cutout
X. Yuan, N. Zhang, M. X. Nguyen, and B. Chen.
Pacific Graphics 2005.
Abstract:
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CSG Operations for Point Models with Implicit Connectivity
N. Zhang, H. Qu, and A. Kaufman.
Computer Graphics International 2005.
Abstract:
We propose Point with Implicit Connectivity (PIC) as a new data structure for representing
solid objects using points. In the PIC representation, an object is adaptively sampled into
an octree, where each leaf cell contains at most one surface component of the object. Each
surface component is represented by a vertex, together with inside/outside classification values
of the cell corners. PIC objects are compact, feature-preserving, and supports easy construction
of the boundary surfaces. To convert geometric objects into the PIC representation, we propose
a sampling algorithm and use quadric error functions as error metrics. For CSG operations between
PIC objects, we present a feature-preserving, adaptive CSG algorithm on the octrees.
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Multiresolution Isosurface Modeling and Rendering
Nan Zhang.
PhD dissertation, Aug. 2004. Advisor: Prof. Arie Kaufman.
Abstract:
This dissertation presents a set of algorithms for modeling and
rendering isosurfaces in multiresolution volume visualization. The
primary contributions are: (1) the introduction of Implicit
Connectivity Mesh (ICM) and its applications, and (2) texturing
volumetric objects and accelerated rendering algorithms for
voxel-based terrain.
The ICM representation is a new type of implicit surfaces. In this
representation, a mesh is composed of vertices only. The space is
partitioned into cubic cells, where each cell may contain one or
more vertices. Each vertex is associated with a connectivity
encoding vector, which implicitly defines the connection of this
vertex with its neighbors. The connectivity information can be the
classification values of cell corner points or the edges/surfaces
intersections of the cell. The explicit polygon mesh can be
quickly reconstructed using the connectivity information stored in
each vertex. Two topology-preserving vertex clustering algorithms,
hierarchical clustering and selective clustering, are used for
creating a multiresolution ICM. Especially, the selective
clustering handles up to four intersection points on a cell edge.
Algorithms for converting isosurfaces of volume datasets and
polygon meshes into the ICM representation are also presented.
...More...
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SHIC: A View-Dependent Rendering Framework for Isosurfaces
N. Zhang, H. Qu, W. Hong and A. Kaufman.
To appear in IEEE/SIGGRAPH Symposium on Volume Visualization 2004.
Abstract:
We propose Selective and Hierarchical Isopoint Clustering (SHIC) as a framework
for interactive isosurface visualization. SHIC is an octree-based vertex hierarchy where each
surface component in a cell is represented by a vertex (isopoint) with encoded connectivity.
We propose a novel connectivity encoding scheme, called Connectivity Encoding Bitmap, and two
topology-preserving isopoint clustering algorithms to build the vertex hierarchy. Our framework
is able to cluster surface components with up to four intersection points on a cell edge. During
rendering, an incremental isosurface extraction algorithm is used to construct the isosurface
dynamically. Events associated with vertex tree modifications and active vertices changes are unified
using timestamps. Our framework is efficient, space-saving, and suitable for rendering large
isosurface objects with local modifications.
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Dual Contouring with Topology-Preserving Simplification Using Enhanced Cell Representation
N. Zhang, W. Hong and A. Kaufman.
To appear in IEEE Visualization 2004.
Abstract:
To preserve topology, multiresolution isosurface extraction algorithms extract and maintain all
critical points. However, this method lowers the simplification capability at the regions containing
critical points. We devise a different approach: preserving the disconnected surface components in cells
during isosurface simplification. We represent isosurface components in a novel representation---enhanced
cell, where surface components in a cell are represented by vertices with connectivity information. A
topology-preserving vertex clustering algorithm is applied to build a vertex octree. An enhanced dual
contouring algorithm is proposed to extract error-bounded multiresolution isosurfaces from the vertex
octree while preserving the finest resolution isosurface topology. Cells containing multiple representative
vertices are properly handled. Several selection strategies for active vertices are supported.
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Feature Preserving Distance Fields
H. Qu, N. Zhang, R. Shao, A. Kaufman and K. Mueller.
To appear in IEEE/ SIGGRAPH Symposium on Volume Visualization 2004.
Abstract:
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Interactive Stereoscopic Rendering of Volumetric Environments
M. Wan, N. Zhang, H. Qu, and A. Kaufman.
IEEE Trans. on Visualization and Computer Graphics, Vol. 10, No. 1, pages 15-28, 2004.
Abstract:
We present an efficient stereoscopic rendering algorithm supporting interactive navigation
inside large-scale 3D voxel-based environments (in short, volumetric environments). In this algorithm,
most of the pixel values of the right image are derived from the left image by a fast 3D warping based
on our stereoscopic projection geometry. A fast volumetric ray casting then fills the remaining gaps
in the warped right image. Our algorithm has been parallelized on a multiprocessor by employing effective
task partitioning schemes and achieved a high cache performance and load balancing. We have applied our
algorithm in two virtual navigation systems, flythrough over terrain and virtual colonoscopy, and reached
interactive stereoscopic rendering rates of more than 10 frames per second on a 16-processor SGI Challenge.
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Ray Tracing Height Fields
H. Qu and Q. Feng and N. Zhang and A. Kaufman.
In Computer Graphics International, July 2003.
Abstract:
We present a novel surface reconstruction algorithm which can directly reconstruct surfaces with different
levels of smoothness in one framework from height fields using 3D discrete grid ray tracing. Our algorithm
exploits the 2.5D nature of the elevation data and the regularity of the rectangular grid from which the
height field surface is sampled. Based on this reconstruction method, we also develop a hybrid rendering
method which has the features of both rasterization and ray tracing. This hybrid method is designed to take
advantage of GPUs newly available flexibility and processing power.
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Multiresolution Volume Simplification and Polygonization
N. Zhang and A. Kaufman.
In International Workshop on Volume Graphics, July 2003.
Abstract:
We propose a multiresolution volume simplification and polygonization algorithm. Traditionally,
voxel-based algorithms lack the adaptive resolution support and consequently simplified volumes
quickly lose sharp features after several levels of downsampling, while tetrahedral-based simplification
algorithms usually generate poorly shaped triangles. In our method, each boundary cell is represented by
a carefully selected representative vertex. The quadric error metrics are applied as the geometric error
metric. Our approach first builds an error pyramid by bottom-up cell merging. We avoid topology problems
in hierarchical cell merging by disabling erroneous cells and penalizing cells containing disconnected
surface components with additional costs. Then, a top-down traversal is used to collect cells within a
user specified error threshold. The surfacenets algorithm is used to polygonize these cells. We enhance
it with online triangle shape optimization and budget control. Finally, we discuss a novel octree implementation
which greatly eases the polygonization operations.
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Interactive Stereoscopic Rendering of Voxel-based Terrain
M. Wan, N. Zhang, H. Qu, and A. Kaufman.
In IEEE Virtual Reality, pages 197-206, 2000.
Abstract:
We present an interactive stereoscopic rendering algorithm of voxel-based terrain. It provides unambiguous
depth information of a terrain scene by generating perspective images for a pair of eyes with a horizontal
parallax. The left-eye image is generated using a fast ray casting algorithm accelerated by exploiting a
specific ray coherence in the voxel-based terrain scene. The right-eye image is obtained by exploiting the
frame coherence between the two views. Most of the pixel values are directly obtained from the left image
by reprojection. The remaining pixels are computed by ray casting, while further accelerated with ray coherence.
An A-buffer is employed to reduce image error caused by reprojection to non-integer pixel locations.
Image-based task partitioning schemes are explored to effectively parallelize our algorithm on a multiprocessor.
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Real Time Volume Rendering
A. Kaufman, F. Dachille, B. Chen, I. Bitter, K. Kreeger, N. Zhang, Q. Tang, and H. Hua.
In Special Issue on 3D Imaging of the International Journal of Imaging Systems and Technology, pages 44-52, 2000.
Abstract:
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