(Press-News.org) The State Key Laboratory of Virtual Reality Technology and Systems, Beihang University in Beijing, has proposed an image based modeling method for inhomogeneous single-scattering participating media whose density fields may contain high frequency details [1]. This work could reduce the difficulty in capturing real-world participating media, which can be applied to 3D games, film production, virtual reality systems, etc. This study is reported in Volume 53 (June, 2010) of the Science China Information Sciences journal because of its significant research value.
Realistic modeling of real-world objects is one of the most important topics in the area of Virtual Reality [2]. Currently, geometric modeling of solid objects has made much headway [3], whilst the modeling of dynamic and fluidic participating media is less studied. Rich visual effects can be produced through the interaction between participating media and lighting, such as a scene shrouded with mist, an arena with smoke and various lighting sources coexisting, or the process of red wine or milk diffusing in water, etc. Therefore, a model for realistic participating media is of great value in enhancing immersion into a virtual environment. The propagation of light in participating media is a very complex process, involving three phenomena: scattering, absorption and media self-emission. The intensity perceived by one's line of sight is the integration of the intensities at all positions along the line within the media that traverses all three phenomena [4]. As it is very difficult to construct the dynamic density field of inhomogeneous participating media and make realistic visual effects with traditional methods (e.g., using particle systems and hydrodynamic equations), the modeling of participating media is an extremely difficult issue in Virtual Reality and Computer Graphics. Currently, the rapid development of digital imaging technology makes it possible to fabricate devices for capturing the real interaction process between lighting and participating media. The fabrication of devices and the use of image-based modeling methods are the main directions of the related research.
So far, related work that can reconstruct the participating media with high frequency detail needs to make good use of complex optical devices such as lasers and high-speed projectors. We focus on proposing an image based modeling method in which the inputs are only a few images. Therefore, in this work, we propose a method to reconstruct inhomogeneous single-scattering participating media, which could preserve the fine high-frequency details of the density fields. Volumetric data and the ratio of the absorption coefficient to the scattering coefficient are used to describe the spatial-varying density distribution and optical properties of certain participating media, and a function relating the above parameters and the captured pixel values is developed. Thus, the problem of how to find solutions to these parameters is formulated as a nonlinear numerical optimization problem. To reduce large time overheads and numerical instability brought about by simultaneously solving large numbers of voxels, we propose an initialization algorithm for enabling the assigned density values to satisfy the regularity of brightness distribution in captured images, in a manner that is nearly as good as the progressive refinement algorithm for multi-resolution volumetric data. Moreover, we propose a parallel multi-voxel gradient computation algorithm using hardware acceleration to reduce the time overheads in the gradient computation of large numbers of voxels.
INFORMATION:
The authors are affiliated to the State Key Laboratory of Virtual Reality Technology and Systems, Beihang University. This laboratory is conducting research mainly in four areas: Modeling Theory and Methodology in Virtual Reality, Augmented Reality and Human-computer Interaction Mechanisms, Distributed Virtual Reality Methods and Techniques, and Virtual Reality Platform Tools and Systems. The third author of this paper is affiliated to Microsoft Research Asia.
Funding from the National Natural Science Foundation of China (Grant Nos. 60773153), 863 Plan of China (Grant No. 2009AA012102) and the Beijing Natural Science Foundation (Grant No. 4102037) supported this research.
7 References:
[1] Hu Y, Qi Y, Tong X .Image-based modeling of inhomogeneous single-scattering participating media. Sci China Inf Sci, 2010, 53:1141�, doi:10.1007/s11432-010-0104-y
http://china.springerlink.com/content/k06640xn3713523r/?p=b25bc232b1f6425aab11ed22a34fa38eπ=0
[2] Zhao Q P. A survey on virtual reality. Science in China Series F: Information Sciences, 2009, 52(3): 348--400
http://china.springerlink.com/content/3413x5245x280801/?p=97af227d5ac24d6985c7c3b5bf35946dπ=0
[3] Qi Y, Yang S, Cai S, et al. A method of 3D modeling and codec. Science in China Series F: Information Sciences, 2009, 52(5): 758--769
http://china.springerlink.com/content/5m52t54423t0r764/?p=97af227d5ac24d6985c7c3b5bf35946dπ=1
[4] Siegel R, Howell J R. Thermal radiation heat transfer. 2nd ed. Washington: Hemisphere Pub. Corp., 1981. 412--484
Nurses have a responsibility to respect and support patients who use cannabis for medicinal purposes, but must stay within the law and follow professional guidance at all times, according to a research review in the September issue of the Journal of Clinical Nursing.
Dr Anita Green and Dr Kay De-Vries studied more than 50 published papers, together with professional and Government guidance documents, official reports and media coverage, from 1996 to 2009.
They point out that the fact that the cannabis is usually obtained illegally can have consequences for those who ...
ESA's Herschel infrared space observatory has discovered that ultraviolet starlight is the key ingredient for making water in space. It is the only explanation for why a dying star is surrounded by a gigantic cloud of hot water vapour.
Every recipe needs a secret ingredient. When astronomers discovered an unexpected cloud of water vapour around the old star IRC+10216 in 2001, they immediately began searching for the source. Stars like IRC+10216 are known as carbon stars and are thought not to make much water. Initially they suspected the star's heat must be evaporating ...
People who take oral bisphosphonates for bone disease over five years may be doubling their risk of developing oesophageal cancer (cancer of the gullet), according to a new study published on bmj.com today.
Oral bisphosphonates are a type of drug used to treat osteoporosis and other bone diseases and are the most commonly recommended treatment for such conditions.
Case reports suggest an association between use of oral bisphosphonates for osteoporosis and increased risk of oesophageal cancer. But the evidence is limited, and no adequately large study with information ...
Interim results from the first comprehensive evaluation of the implementation of electronic health records in secondary care in England have found delays and frustration with the system, according to research published on bmj.com today.
The authors, led by Professor Aziz Sheikh from The University of Edinburgh (and which included researchers from The London School of Economics and Political Science, The School of Pharmacy and The University of Nottingham), say experiences from the first-wave implementation site "indicate that delivering improved healthcare through nationwide ...
Scientists have built a clearer picture of how lengthy strands of DNA are concertinaed when our cells grow and divide, in a discovery could help explain how cell renewal can go wrong.
Scientists have identified thousands of proteins that play a key role in compacting DNA – a crucial process by which DNA is shortened up to 10,000 times to fit inside cells as they split into two.
Researchers hope the findings could shed light on what happens when this packaging process fails and cells divide abnormally – which can lead to cancer or cause developing embryos to miscarry.
Scientists ...
Biophysicists in Bochum have discovered a diode for protons: just like the electronic component determines the direction of flow of electric current, the "proton diode" ensures that protons can only pass through a cell membrane in one direction. Water molecules play an important role here as active components of the diode. The researchers led by Prof. Dr. Klaus Gerwert (Chair of Biophysics at the RUB) were able to observe this through a combination of molecular biology, X-ray crystallography, time-resolved FTIR spectroscopy and biomolecular simulations. They report in the ...
For severe migraine sufferers, psychological treatments build on the benefits of drug therapy, according to a new study1 by Elizabeth Seng and Dr. Kenneth Holroyd from Ohio University in the US. Their comparison of the effects of various treatment combinations for severe migraine – drug therapy with or without behavioral management – shows that those patients receiving the behavioral management program alongside drug therapy are significantly more confident in their ability to use behavioral skills to effectively self-manage migraines. And surprisingly, the increase in ...
A chemical analysis of the bones of ancient Nubians shows that they were regularly consuming tetracycline, most likely in their beer. The finding is the strongest evidence yet that the art of making antibiotics, which officially dates to the discovery of penicillin in 1928, was common practice nearly 2,000 years ago.
The research, led by Emory University anthropologist George Armelagos and medicinal chemist Mark Nelson of Paratek Pharmaceuticals, Inc., is in the current issue of the American Journal of Physical Anthropology.
"We tend to associate drugs that cure diseases ...
A new study from the Center for Interdisciplinary Chronobiological Research at the University of Haifa has found an additional link between Light At Night (LAN) and cancer. This research joins a series of earlier studies carried out at the University of Haifa that also established the correlation. "High power light bulbs contribute more to 'environmental light pollution', which the study has shown is a carcinogenic pollution," notes Prof. Abraham Haim, who headed the study.
Earlier studies in which Prof. Haim has participated at the University of Haifa, have shown that ...
A team of McGill chemists have discovered that a technique known as photoacoustic infrared spectroscopy could be used to identify the composition of pigments used in art work that is decades or even centuries old. Pigments give artist's materials colour, and they emit sounds when light is shone on them.
"The chemical composition of pigments is important to know, because it enables museums and restorers to know how the paints will react to sunlight and temperature changes," explained Dr. Ian Butler, lead researcher and professor at McGill's Department of Chemistry. Without ...
