3,842 research outputs found
NePF: Neural Photon Field for Single-Stage Inverse Rendering
We present a novel single-stage framework, Neural Photon Field (NePF), to
address the ill-posed inverse rendering from multi-view images. Contrary to
previous methods that recover the geometry, material, and illumination in
multiple stages and extract the properties from various multi-layer perceptrons
across different neural fields, we question such complexities and introduce our
method - a single-stage framework that uniformly recovers all properties. NePF
achieves this unification by fully utilizing the physical implication behind
the weight function of neural implicit surfaces and the view-dependent
radiance. Moreover, we introduce an innovative coordinate-based illumination
model for rapid volume physically-based rendering. To regularize this
illumination, we implement the subsurface scattering model for diffuse
estimation. We evaluate our method on both real and synthetic datasets. The
results demonstrate the superiority of our approach in recovering high-fidelity
geometry and visual-plausible material attributes
Report on shape analysis and matching and on semantic matching
In GRAVITATE, two disparate specialities will come together in one working platform for the archaeologist: the fields of shape analysis, and of metadata search. These fields are relatively disjoint at the moment, and the research and development challenge of GRAVITATE is precisely to merge them for our chosen tasks. As shown in chapter 7 the small amount of literature that already attempts join 3D geometry and semantics is not related to the cultural heritage domain. Therefore, after the project is done, there should be a clear ‘before-GRAVITATE’ and ‘after-GRAVITATE’ split in how these two aspects of a cultural heritage artefact are treated.This state of the art report (SOTA) is ‘before-GRAVITATE’. Shape analysis and metadata description are described separately, as currently in the literature and we end the report with common recommendations in chapter 8 on possible or plausible cross-connections that suggest themselves. These considerations will be refined for the Roadmap for Research deliverable.Within the project, a jargon is developing in which ‘geometry’ stands for the physical properties of an artefact (not only its shape, but also its colour and material) and ‘metadata’ is used as a general shorthand for the semantic description of the provenance, location, ownership, classification, use etc. of the artefact. As we proceed in the project, we will find a need to refine those broad divisions, and find intermediate classes (such as a semantic description of certain colour patterns), but for now the terminology is convenient – not least because it highlights the interesting area where both aspects meet.On the ‘geometry’ side, the GRAVITATE partners are UVA, Technion, CNR/IMATI; on the metadata side, IT Innovation, British Museum and Cyprus Institute; the latter two of course also playing the role of internal users, and representatives of the Cultural Heritage (CH) data and target user’s group. CNR/IMATI’s experience in shape analysis and similarity will be an important bridge between the two worlds for geometry and metadata. The authorship and styles of this SOTA reflect these specialisms: the first part (chapters 3 and 4) purely by the geometry partners (mostly IMATI and UVA), the second part (chapters 5 and 6) by the metadata partners, especially IT Innovation while the joint overview on 3D geometry and semantics is mainly by IT Innovation and IMATI. The common section on Perspectives was written with the contribution of all
Dynamic Multivariate Simplex Splines For Volume Representation And Modeling
Volume representation and modeling of heterogeneous objects acquired from real world are very challenging research tasks and playing fundamental roles in many potential applications, e.g., volume reconstruction, volume simulation and volume registration. In order to accurately and efficiently represent and model the real-world objects, this dissertation proposes an integrated computational framework based on dynamic multivariate simplex splines (DMSS) that can greatly improve the accuracy and efficacy of modeling and simulation of heterogenous objects. The framework can not only reconstruct with high accuracy geometric, material, and other quantities associated with heterogeneous real-world models, but also simulate the complicated dynamics precisely by tightly coupling these physical properties into simulation. The integration of geometric modeling and material modeling is the key to the success of representation and modeling of real-world objects.
The proposed framework has been successfully applied to multiple research areas, such as volume reconstruction and visualization, nonrigid volume registration, and physically based modeling and simulation
Reconstructing Cardiac Electrical Excitations from Optical Mapping Recordings
The reconstruction of electrical excitation patterns through the unobserved
depth of the tissue is essential to realizing the potential of computational
models in cardiac medicine. We have utilized experimental optical-mapping
recordings of cardiac electrical excitation on the epicardial and endocardial
surfaces of a canine ventricle as observations directing a local ensemble
transform Kalman Filter (LETKF) data assimilation scheme. We demonstrate that
the inclusion of explicit information about the stimulation protocol can
marginally improve the confidence of the ensemble reconstruction and the
reliability of the assimilation over time. Likewise, we consider the efficacy
of stochastic modeling additions to the assimilation scheme in the context of
experimentally derived observation sets. Approximation error is addressed at
both the observation and modeling stages, through the uncertainty of
observations and the specification of the model used in the assimilation
ensemble. We find that perturbative modifications to the observations have
marginal to deleterious effects on the accuracy and robustness of the state
reconstruction. Further, we find that incorporating additional information from
the observations into the model itself (in the case of stimulus and stochastic
currents) has a marginal improvement on the reconstruction accuracy over a
fully autonomous model, while complicating the model itself and thus
introducing potential for new types of model error. That the inclusion of
explicit modeling information has negligible to negative effects on the
reconstruction implies the need for new avenues for optimization of data
assimilation schemes applied to cardiac electrical excitation.Comment: main text: 18 pages, 10 figures; supplement: 5 pages, 9 figures, 2
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Resolving the obscuring torus in NGC 1068 with the power of infrared interferometry: Revealing the inner funnel of dust
We present new interferometric data obtained with MIDI (MID infrared
Interferometric instrument) for the Seyfert II galaxy NGC 1068, with an
extensive coverage of sixteen uv points. These observations resolve the nuclear
mid-infrared emission from NGC 1068 in unprecedented detail with a maximum
resolution of 7 mas. For the first time, sufficient uv points have been
obtained, allowing us to generate an image of the source using maximum entropy
image reconstruction. The features of the image are similar to those obtained
by modelling. We find that the mid-infrared emission can be represented by two
components, each with a Gaussian brightness distribution. The first, identified
as the inner funnel of the obscuring torus, is hot (800K), 1.35 parsec long,
and 0.45 parsec thick in FWHM at a PA=-42 degrees (from north to east). It has
an absorption profile different than standard interstellar dust and with
evidence for clumpiness. The second component is 3 by 4 pc in FWHM with T=300K,
and we identify it with the cooler body of the torus. The compact component is
tilted by 45 degrees with respect to the radio jet and has similar size and
orientation to the observed water maser distribution. We show how the dust
distribution relates to other observables within a few parsecs of the core of
the galaxy such as the nuclear masers, the radio jet, and the ionization cone.
We compare our findings to a similar study of the Circinus galaxy and other
relevant studies. Our findings shed new light on the relation between the
different parsec-scale components in NGC 1068 and the obscuring torus.Comment: Accepted to MNRA
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