6 research outputs found
Iterative stripification of a triangle mesh: focus on data structures
In this paper we describe the data structure and some implementation details of the tunneling algorithm for generating
a set of triangle strips from a mesh of triangles. The algorithm uses a simple topological operation on the dual graph
of the mesh, to generate an initial stripification and iteratively rearrange and decrease the number of strips. Our
method is a major improvement of a proposed one originally devised for both static and continuous level-of-detail
(CLOD) meshes and retains this feature. The usage of a dynamical identification strategy for the strips allows us to
drastically reduce the length of the searching paths in the graph needed for the rearrangement and produce loop-free
triangle strips without any further controls and post-processing, while requiring a more sophisticated implementation
to manage the search and undo operations
Novel methods of image compression for 3D reconstruction
Data compression techniques are widely used in the transmission and storage of 2D
image, video and 3D data structures. The thesis addresses two aspects of data
compression: 2D images and 3D structures by focusing research on solving the
problem of compressing structured light images for 3D reconstruction. It is useful then
to describe the research by separating the compression of 2D images from the
compression of 3D data. Concerning image compression, there are many types of
techniques and among the most popular are JPEG and JPEG2000. The thesis
addresses different types of discrete transformations (DWT, DCT and DST)
thatcombined in particular ways followed by Matrix Minimization algorithm,which is
achieved high compression ratio by converting groups of data into a single value. This
is an essential step to achieve higher compression ratios reaches to 99%. It is
demonstrated that the approach is superior to both JPEG and JPEG2000 for
compressing 2D images used in 3D reconstruction. The approach has also been tested
oncompressing natural or generic 2D images mainly through DCT followed by Matrix
Minimization and arithmetic coding.Results show that the method is superior to JPEG
in terms of compression ratios and image quality, and equivalent to JPEG2000 in
terms of image quality.
Concerning the compression of 3D data structures, the Matrix Minimization algorithm
is used to compress geometry and connectivity represented by a list of vertices and a
list of triangulated faces. It is demonstrated that the method can compress vertices
very efficiently compared with other 3D formats. Here the Matrix Minimization
algorithm converts each vertex (X, Y and Z) into a single value without the use of any
prior discrete transformation (as used in 2D images) and without using any coding
algorithm. Concerningconnectivity,the triangulated face data are also compressed with
the Matrix Minimizationalgorithm followed by arithmetic coding yielding a stream of
compressed data. Results show compression ratiosclose to 95% which are far superior
to compression with other 3D techniques.
The compression methods presented in this thesis are defined as per-file compression.
The methods to generate compression keys depend on the data to be compressed.
Thus, each file generates their own set of compression keys and their own set of
unique data. This feature enables application in the security domain for safe
transmission and storage of data. The generated keys together with the set of unique
data can be defined as an encryption key for the file as, without this information, the
file cannot be decompressed