A survey of real-time crowd rendering

In this survey we review, classify and compare existing approaches for real-time crowd rendering. We first overview character animation techniques, as they are highly tied to crowd rendering performance, and then we analyze the state of the art in crowd rendering. We discuss different representations for level-of-detail (LoD) rendering of animated characters, including polygon-based, point-based, and image-based techniques, and review different criteria for runtime LoD selection. Besides LoD approaches, we review classic acceleration schemes, such as frustum culling and occlusion culling, and describe how they can be adapted to handle crowds of animated characters. We also discuss specific acceleration techniques for crowd rendering, such as primitive pseudo-instancing, palette skinning, and dynamic key-pose caching, which benefit from current graphics hardware. We also address other factors affecting performance and realism of crowds such as lighting, shadowing, clothing and variability. Finally we provide an exhaustive comparison of the most relevant approaches in the field.Peer ReviewedPostprint (author's final draft

Interacting supernovae and supernova impostors. SN 2007sv: the major eruption of a massive star in UGC 5979

We report the results of the photometric and spectroscopic monitoring campaign of the transient SN 2007sv. The observables are similar to those of type IIn supernovae, a well-known class of objects whose ejecta interact with pre-existing circum-stellar material. The spectra show a blue continuum at early phases and prominent Balmer lines in emission, however, the absolute magnitude at the discovery of SN 2007sv (M_R = - 14.25 +/- 0.38) indicate it to be most likely a supernova impostor. This classification is also supported by the lack of evidence in the spectra of very high velocity material as expected in supernova ejecta. In addition we find no unequivocal evidence of broad lines of alpha - and/or Fe-peak elements. The comparison with the absolute light curves of other interacting objects (including type IIn supernovae) highlights the overall similarity with the prototypical impostor SN 1997bs. This supports our claim that SN 2007sv was not a genuine supernova, and was instead a supernova impostor, most likely similar to the major eruption of a luminous blue variable.Comment: Accepted for publication in MNRAS. 15 pages, 11 figures, 5 table

It is a Graviton! or maybe not

The discovery of Kaluza-Klein (KK) gravitons is a smoking gun of extra dimensions. Other scenarios, however, could give rise to spin-two resonances of a new strongly-coupled sector and act as impostors. In this paper we prove that a spin-two resonance does not couple to the Standard Model through dimension-four operators. We then show that the massive graviton and its impostor both couple to the Standard Model through the same dimension-five operators. Therefore the spin determination is identical. Nevertheless, we also show that one can use the ratio of branching ratios to photons and to jets for distinguishing between KK gravitons and their impostors. The capacity to distinguish between KK gravitons and impostors is a manifestation of the breakdown of the duality between AdS and strongly-coupled theories.Comment: 14 pages, 3 figures, 1 table. References added, typos correcte

Constraints for the Progenitor Masses of Historic Core-Collapse Supernovae

We age-date the stellar populations associated with 12 historic nearby core-collapse supernovae (CCSNe) and 2 supernova impostors, and from these ages, we infer their initial masses and associated uncertainties. To do this, we have obtained new HST imaging covering these CCSNe. Using these images, we measure resolved stellar photometry for the stars surrounding the locations of the SNe. We then fit the color-magnitude distributions of this photometry with stellar evolution models to determine the ages of any young existing populations present. From these age distributions, we infer the most likely progenitor mass for all of the SNe in our sample. We find ages between 4 and 50 Myr, corresponding to masses from 7.5 to 59 solar masses. There were no SNe that lacked a young population within 50~pc. Our sample contains 4 type Ib/c SNe; their masses have a wide range of values, suggesting that the progenitors of stripped-envelope SNe are binary systems. Both impostors have masses constrained to be $\lesssim$7.5 solar masses. In cases with precursor imaging measurements, we find that age-dating and precursor imaging give consistent progenitor masses. This consistency implies that, although the uncertainties for each technique are significantly different, the results of both are reliable to the measured uncertainties. We combine these new measurements with those from our previous work and find that the distribution of 25 core-collapse SNe progenitor masses is consistent with a standard Salpeter power-law mass function, no upper mass cutoff, and an assumed minimum mass for core-collapse of 7.5~M$_{\odot}$.Comment: 12 pages, 4 tables, 4 figures, accepted for publication in Ap

A Revised Historical Light Curve of Eta Carinae and the Timing of Close Periastron Encounters

The historical light curve of the 19th century "Great Eruption" of etaCar provides a striking record of violent instabilies encountered by the most massive stars. We report and analyze newly uncovered historical estimates of the visual brightness of etaCar during its eruption, and we correct some mistakes in the original record. The revised light curve looks substantially different from previous accounts: it shows two brief eruptions in 1838 and 1843 that resemble modern supernova impostors, while the final brightening in December 1844 marks the time when etaCar reached its peak brightness. We consider the timing of brightening events as they pertain to the putative binary system in etaCar: (1) The brief 1838 and 1843 events peaked within weeks of periastron if the pre-1845 orbital period is shorter than at present due to the mass loss of the eruption. Each event lasted only 100 days. (2) The main brightening at the end of 1844 has no conceivable association with periastron, beginning more than 1.5yr afterward. It lasted 10yr, with no obvious influence of periastron encounters during that time. (3) The 1890 eruption began to brighten at periastron, but took over 1yr to reach maximum and remained there for almost 10yr. A second periastron passage midway through the 1890 eruption had no effect. While evidence for a link between periastron encounters and the two brief precursor events is compelling, the differences between the three cases above make it difficult to explain all three phenomena with the same mechanism.Comment: 11 pages, 4 figures. submitted to MNRAS on october 12. updated reference

Interactive inspection of complex multi-object industrial assemblies

The final publication is available at Springer via http://dx.doi.org/10.1016/j.cad.2016.06.005The use of virtual prototypes and digital models containing thousands of individual objects is commonplace in complex industrial applications like the cooperative design of huge ships. Designers are interested in selecting and editing specific sets of objects during the interactive inspection sessions. This is however not supported by standard visualization systems for huge models. In this paper we discuss in detail the concept of rendering front in multiresolution trees, their properties and the algorithms that construct the hierarchy and efficiently render it, applied to very complex CAD models, so that the model structure and the identities of objects are preserved. We also propose an algorithm for the interactive inspection of huge models which uses a rendering budget and supports selection of individual objects and sets of objects, displacement of the selected objects and real-time collision detection during these displacements. Our solution–based on the analysis of several existing view-dependent visualization schemes–uses a Hybrid Multiresolution Tree that mixes layers of exact geometry, simplified models and impostors, together with a time-critical, view-dependent algorithm and a Constrained Front. The algorithm has been successfully tested in real industrial environments; the models involved are presented and discussed in the paper.Peer ReviewedPostprint (author's final draft