What can we see from the road? Applications of a cumulative viewshed analysis on a US state highway network

In many parts of the world, motorized travel is one of the most common ways that people interact with their regional landscape. This study investigates how travelers\u27 understandings of place might be influenced by what landforms they can see from a vehicle. It uses a cumulative viewshed analysis on the Washington State (United States) highway network to determine which physical landscape features are most frequently visible or obscured from the road. Adapting ideas from Kevin Lynch\u27s The Image of the City, I propose spatial data processing methods to derive landmarks, edges, and districts that could most contribute to the mental maps of travelers and should be prioritized for labeling on print, electronic, and augmented reality maps. Other applications of the cumulative viewshed include deriving scenic byways, siting proposed construction for high or low visibility, and guiding conversations about critical toponymy and perceptions of place

Fast photorealistic techniques to simulate global illumination in videogames and virtual environments

Per al càlcul de la il·luminació global per a la síntesi d'imatges d'escenaris virtuals s'usen mètodes físicament acurats com a radiositat o el ray-tracing. Aquests mètodes són molt potents i capaços de generar imatges de gran realisme, però són molt costosos. A aquesta tesi presenta algunes tècniques per simular i/o accelerar el càlcul de la il·luminació global. La tècnica de les obscurances es basa en la suposició que com més amagat és un punt a l'escena, més fosc s'ha de veure. Es calcula analitzant l'entorn geomètric del punt i ens dóna un valor per a la seva il·luminació indirecta, que no és físicament acurat, però sí aparentment realista.Aquesta tècnica es millora per a entorns en temps real com els videojocs. S'aplica també a entorns de ray-tracing per a la generació d'imatges realistes. En aquest context, el càlcul de seqüències de frames per a l'animació de llums i càmeres s'accelera enormement reusant informació entre frames.Les obscurances serveixen per a simular la il·luminació indirecta d'una escena. La llum directa es calcula apart i de manera independent. El desacoblament de la llum directa i la indirecta és una gran avantatge, i en treurem profit. Podem afegir fàcilment l'efecte de coloració entre objectes sense afegir temps de càlcul. Una altra avantatge és que per calcular les obscurances només hem d'analitzar un entorn limitat al voltant del punt.Per escenes virtuals difuses, la radiositat es pot precalcular i l'escena es pot navegar amb apariència realista, però si un objecte de l'escena es mou en un entorn dinàmic en temps real, com un videojoc, el recàlcul de la il·luminació global de l'escena és prohibitiu. Com les obscurances es calculen en un entorn limitat, es poden recalcular en temps real per a l'entorn de l'objecte que es mou a cada frame i encara aconseguir temps real.A més, podem fer servir les obscurances per a calcular imatges de gran qualitat, o per seqüències d'imatges per una animació, com en el ray-tracing. Això ens permet tractar materials no difusos i investigar l'ús de tècniques normalment difuses com les obscurances en entorns generals. Quan la càmera està estàtica, l'ús d'animació de llum només afecta la il·luminació directa, i si usem obscurances per a la llum indirecta, gràcies al seu desacoblament, el càlcul de sèries de frames per a una animació és molt ràpid. El següent pas és afegir animació de càmera, reusant els valors de les obscurances entre frames. Aquesta última tècnica de reús d'informació de la il·luminació del punt d'impacte entre frames la podem usar per a tècniques acurades d'il·luminació global com el path-tracing, i nosaltres estudiem com reusar aquesta informació de manera no esbiaixada. A més, estudiem diferents tècniques de mostreig per a la semi-esfera, i les obscurances es calculen amb una nova tècnica, aplicant depth peeling amb GPU.To compute global illumination solutions for rendering virtual scenes, physically accurate methods based on radiosity or ray-tracing are usually employed. These methods, though powerful and capable of generating images with high realism, are very costly. In this thesis, some techniques to simulate and/or accelerate the computation of global illumination are studied. The obscurances technique is based on the supposition that the more occluded is a point in the scene, the darker it will appear. It is computed by analyzing the geometric environment of the point and gives a value for the indirect illumination for the point that is, though not physically accurate, visually realistic. This technique is enhanced and improved in real-time environments as videogames. It is also applied to ray-tracing frameworks to generate realistic images. In this last context, sequences of frames for animation of lights and cameras are dramatically accelerated by reusing information between frames.The obscurances are computed to simulate the indirect illumination of a scene. The direct lighting is computed apart and in an independent way. The decoupling of direct and indirect lighting is a big advantage, and we will take profit from this. We can easily add color bleeding effects without adding computation time. Another advantage is that to compute the obscurances we only need to analyze a limited environment around the point. For diffuse virtual scenes, the radiosity can be precomputed and we can navigate the scene with a realistic appearance. But when a small object moves in a dynamic real-time virtual environment, as a videogame, the recomputation of the global illumination of the scene is prohibitive. Thanks to the limited reach of the obscurance computation, we can recompute the obscurances only for the limited environment of the moving object for every frame and still have real-time frame rates. Obscurances can also be used to compute high quality images, or sequences of images for an animation, in a ray-tracing-like. This allows us to deal with non-diffuse materials and to research the use of a commonly diffuse technique as obscurances in general environments. For static cameras, using light animation only affects to direct lighting, and if we use obscurances for the indirect lighting, thanks to the decoupling of direct and indirect illumination, the computation of a series of frames for the animation is very fast. The next step is to add camera animation, reusing the obscurances results between frames. Using this last technique of reusing the illumination of the hit points between frames for a true global illumination technique as path tracing, we study how we can reuse this information in an unbiased way. Besides, a study of different sampling techniques for the hemisphere is made, obscurances are computed with the depth-peeling technique and using GPU

Seven HCI Grand Challenges

This article aims to investigate the Grand Challenges which arise in the current and emerging landscape of rapid technological evolution towards more intelligent interactive technologies, coupled with increased and widened societal needs, as well as individual and collective expectations that HCI, as a discipline, is called upon to address. A perspective oriented to humane and social values is adopted, formulating the challenges in terms of the impact of emerging intelligent interactive technologies on human life both at the individual and societal levels. Seven Grand Challenges are identified and presented in this article: Human-Technology Symbiosis; Human-Environment Interactions; Ethics, Privacy and Security; Well-being, Health and Eudaimonia; Accessibility and Universal Access; Learning and Creativity; and Social Organization and Democracy. Although not exhaustive, they summarize the views and research priorities of an international interdisciplinary group of experts, reflecting different scientific perspectives, methodological approaches and application domains. Each identified Grand Challenge is analyzed in terms of: concept and problem definition; main research issues involved and state of the art; and associated emerging requirements

Sparse Volumetric Deformation

Volume rendering is becoming increasingly popular as applications require realistic solid shape representations with seamless texture mapping and accurate filtering. However rendering sparse volumetric data is difficult because of the limited memory and processing capabilities of current hardware. To address these limitations, the volumetric information can be stored at progressive resolutions in the hierarchical branches of a tree structure, and sampled according to the region of interest. This means that only a partial region of the full dataset is processed, and therefore massive volumetric scenes can be rendered efficiently. The problem with this approach is that it currently only supports static scenes. This is because it is difficult to accurately deform massive amounts of volume elements and reconstruct the scene hierarchy in real-time. Another problem is that deformation operations distort the shape where more than one volume element tries to occupy the same location, and similarly gaps occur where deformation stretches the elements further than one discrete location. It is also challenging to efficiently support sophisticated deformations at hierarchical resolutions, such as character skinning or physically based animation. These types of deformation are expensive and require a control structure (for example a cage or skeleton) that maps to a set of features to accelerate the deformation process. The problems with this technique are that the varying volume hierarchy reflects different feature sizes, and manipulating the features at the original resolution is too expensive; therefore the control structure must also hierarchically capture features according to the varying volumetric resolution. This thesis investigates the area of deforming and rendering massive amounts of dynamic volumetric content. The proposed approach efficiently deforms hierarchical volume elements without introducing artifacts and supports both ray casting and rasterization renderers. This enables light transport to be modeled both accurately and efficiently with applications in the fields of real-time rendering and computer animation. Sophisticated volumetric deformation, including character animation, is also supported in real-time. This is achieved by automatically generating a control skeleton which is mapped to the varying feature resolution of the volume hierarchy. The output deformations are demonstrated in massive dynamic volumetric scenes