A progressive refinement approach for the visualisation of implicit surfaces

Visualising implicit surfaces with the ray casting method is a slow procedure. The design cycle of a new implicit surface is, therefore, fraught with long latency times as a user must wait for the surface to be rendered before being able to decide what changes should be introduced in the next iteration. In this paper, we present an attempt at reducing the design cycle of an implicit surface modeler by introducing a progressive refinement rendering approach to the visualisation of implicit surfaces. This progressive refinement renderer provides a quick previewing facility. It first displays a low quality estimate of what the final rendering is going to be and, as the computation progresses, increases the quality of this estimate at a steady rate. The progressive refinement algorithm is based on the adaptive subdivision of the viewing frustrum into smaller cells. An estimate for the variation of the implicit function inside each cell is obtained with an affine arithmetic range estimation technique. Overall, we show that our progressive refinement approach not only provides the user with visual feedback as the rendering advances but is also capable of completing the image faster than a conventional implicit surface rendering algorithm based on ray casting

Narrative of the Volunteer Camp at Niagara, June 1871

Editor’s Introduction: The Canadian military as we know it emerged in the critical decades that immediately preceded and followed Confederation in 1867. While a number of accounts are available of militia officers’ experiences in these decades, so far we have missed the important perspective of rank and file. Recently, however, an interesting example of such a perspective has come to light and has been added to the collection of the Canadian War Museum (CWM). This is in the form of a short but insightful narrative, written by a Private Andrew Greenhill of Hamilton, Ontario’s 13th Battalion, Canadian Militia, describing his experiences while serving at the Militia Camp held at Niagara in June 1871

Breaking down banners: analytical approaches to determining the materials of painted banners

Background: This paper investigates a range of analytical techniques to yield information about the materials and processes used in making painted banners. A textile conservator, technical art historian and paintings conservator, and materials scientist have joined forces to develop a greater understanding of the potential of analytical findings in the identification of materials. Results: Visual examination using low level magnification and microscopy proved to be a crucial starting point and for identification of areas for further analysis. High magnification microscopy of cross sections was invaluable to gather information regarding the build-up of the layers, their interaction and condition. Scanning electron microscopy (SEM) of ion-milled samples showed that different areas of the banner had been prepared in different ways. SEM-EDX (scanning electron microscopy energy-dispersive X-ray spectroscopy) confirmed the presence of the main elements of pigments. Raman enabled identification of specific pigments. Raman also provided confirmation of specific materials (such as the paint filler). Fourier transform infrared spectroscopy with attenuated total reflectance (FTIR-ATR) enabled the identification of oil and resin, confirmation of pigments and fibres. Thin layers made sampling and identification challenging. Presence of materials such as silk and lead white dominated some analysis making interpretation of other materials more difficult. Conclusions: Sample preparation had a significant bearing on the effectiveness of the analysis. Ion-milling provided high quality surface on the cross section samples that enabled material interfaces to be clearly seen. The challenges of finding effective wavelengths for analysis of samples using Raman were clearly evident in this study. Microscopy showed fibres blends, easily missed using FTIR, whereas FTIR was particularly effective in the identification of man-made fibres. While portable instrumentation may be useful, for in-depth understanding of the heterogeneous layered materials sample taking still remains crucial. Commercial makers used many typical grounds and pigments but these were used sparingly, in thin layers, in order to produce a flexible object and also perhaps to reduce costs. The textile was however of high quality, in this case silk. Unexpectedly, the preparation layers do not appear to be consistent across the banner; the reasons for this need further investigation

Hauntology or the return of the real man: edging the Žižek-Laclau controversy on populism

Looking at today’s academization of everyday life – academic knowledge having become central in mediating the presence of the human being with himself, the others and the world – it seems that academia has become the home-base of post-modern man. Academia is however no viable habitat, the (post)modern subject is pushed to the search to rejoin real life and be a real human being. In this paper it is argued that this is centrally related to the topic of ideology. The dispute between Ernesto Laclau and Slavoj Žižek on populism is re-read in this light as it ultimately boils down to a dispute on what real man is. Laclau’s theory, missing the dimension of the uncanny and the truth shall thus be contrasted with Žižek’s recourse to the idea of hauntology as the latter is the basis for Žižek’s reasserting of what we could call the rock of class struggle. Class struggle furthermore turns out to be also the issue at stake in that other debate of Žižek with Yannis Stavrakakis. In the concluding part the viability of Žižekian hauntology is questioned given the impossible politization of psychoanalysis and its skandalons

Borderline bodies

This chapter is about borders that are made and broken at gay pride parades. Specifically, I examine the discursive and material borders maintained in tourism discourse. Binary oppositions such as self/other, straight/gay, and tourist/host provide a focus for this chapter. I am interested in where these borders wear thin and threaten to break and disrupt social order. I explore the bodies of gay pride parades because it is bodies such as these that threaten the borders of corporeal acceptability

Preparing for War: The 25th Battalion in Halifax, 1914–15

The 25th Battalion was authorized in November 1914 and recruited men from throughout Nova Scotia before departing for England in May 1915. It spent the winter and early spring of 1914–15 in Halifax, where it was based at the Armoury and on the Common. Robert Clements, a native of Yarmouth, enlisted in the battalion in November 1914 and served in it throughout the war, rising to the rank of lieutenant. Many years later he wrote an informal history of the battalion, giving a colourful account based on his personal experiences and observations. These excerpts from his soon to be published manuscript, describe the battalion’s experiences in Halifax as the men trained, coped with inadequate equipment and inexperienced officers, and prepared to go overseas

SurfelMeshing: Online Surfel-Based Mesh Reconstruction

We address the problem of mesh reconstruction from live RGB-D video, assuming a calibrated camera and poses provided externally (e.g., by a SLAM system). In contrast to most existing approaches, we do not fuse depth measurements in a volume but in a dense surfel cloud. We asynchronously (re)triangulate the smoothed surfels to reconstruct a surface mesh. This novel approach enables to maintain a dense surface representation of the scene during SLAM which can quickly adapt to loop closures. This is possible by deforming the surfel cloud and asynchronously remeshing the surface where necessary. The surfel-based representation also naturally supports strongly varying scan resolution. In particular, it reconstructs colors at the input camera's resolution. Moreover, in contrast to many volumetric approaches, ours can reconstruct thin objects since objects do not need to enclose a volume. We demonstrate our approach in a number of experiments, showing that it produces reconstructions that are competitive with the state-of-the-art, and we discuss its advantages and limitations. The algorithm (excluding loop closure functionality) is available as open source at https://github.com/puzzlepaint/surfelmeshing .Comment: Version accepted to IEEE Transactions on Pattern Analysis and Machine Intelligenc

The Albany Movement and the Origin of Freedom Songs

“We became visible.” This is how Bernice Johnson Reagon, a Civil Rights Movement worker, a member of the Freedom Singers, and the founder of Sweet Honey In The Rock explained how songs uplifted and inspired those blacks and whites who worked tirelessly for freedom throughout the 1950’s and 1960’s. Indeed, freedom songs in the movement gave participants the ability to stand up against their fears, express their hopes and desires, and unite the diverse range of people who participated in the movement. Reagon, now a history professor and music legend, grew up right outside of Albany, Georgia, where freedom songs first became an integral part of the Civil Rights Movement. Nestled in a land entrenched with racial segregation, the Albany campaign was notable because almost every single black member of the community became visible through his or her work. Whether it was by going to jail, marching, or attending a mass meeting, most citizens actively participated. Albany was and is still considered today to be one of the birthplaces of the mass movement for racial equality. Albany, therefore, came to symbolize for the larger struggle for black freedom not only the birthplace of a true grassroots campaign, but also the birthplace of freedom songs that would spread throughout the country and become a familiar and helpful tool for many freedom fighters

Visible

I will never know what it means to be invisible. I will never know how it is to be able to kiss carelessly in the park, to just go for it. What it means to stroll in the streets and not have to deal with the fact that somebody might try and touch my hair as they walk by. How it is not to have to constantly self-soothe in monologues after a day of being asked multiple times whether one understands German. To dissolve in the crowd is not an option for me. I belong to several minority groups at once; to conceal this would entail more dangers for me than to name my positionalities