The main objective of this paper is to propose a systematic fieldwork approach in order to describe the ground condition of dense urban riverine settlements. The proposed approach supplements aerial-view acquireddigi...
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The main objective of this paper is to propose a systematic fieldwork approach in order to describe the ground condition of dense urban riverine settlements. The proposed approach supplements aerial-view acquireddigital elevation models that are unable to describe the ground conditions that are obstructed by urban and vegetative canopies. After three years spent developing this approach, we can compare and identify synergies between three ground-view acquisition methods: an action-, digital single lens reflex (dSLR)-camera, and terrestrial laser scanner (TLS). This paper consists of a two-part study, which uses the visual quality and accuracy of the data sets produced as criterion for appraisal. Although norms would suggest a hypothetical best operational workflow as an outcome of this paper, we instead argue that the identification of circumstances in which different methods are combined to complement the limitations of another is more beneficial. As such, through the appraisal of visual quality and accuracy obtained by the approaches described above we can draw better insights to make the most out of typically laborious fieldwork. Given the labour-intensive process, an economy of work is necessitated in order to capture the best description of landscape elements with the given equipment and time, allowing the greatest area of coverage. (C) 2015 Elsevier Ltd. All rights reserved.
image-based3dmodelling using Structure-form-Motion (SfM) has matured significantly over the last decade. Standard SfM methods create the object's texture from the appearance of the physical object at the time of...
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ISBN:
(纸本)9781728109879
image-based3dmodelling using Structure-form-Motion (SfM) has matured significantly over the last decade. Standard SfM methods create the object's texture from the appearance of the physical object at the time of acquisition. We propose a method for acquiring the diffuse per-point reflectance of the modelled object, as part of the image acquisition work flow, only adding one extra capturedimage and an irradiance rendering step, making it easy for anyone to digitize physical objects to create 3d content for AR/VR using only consumer grade hardware. Current state of the art of spatially varying reflectance capture requires either large, expensive, and purpose built setups or are optimization based approaches, whereas the proposed approach is model based. This paper proposes adding a render of irradiance with modelled camera and light source, using off the shelf hardware for image capture. The key element is taking two images at each imaging location: one with just the ambient illumination conditions, and one where the light from an on-camera flash is included. It is demonstrated how to get the ambient illumination to cancel out, and by assuming Lambertian materials, render the irradiance corresponding to the flash-only image, enabling computation of spatially varying diffuse reflectance rather than appearance. Qualitative results demonstrate the added realism of the modelled objects when used as assets in renders under varying illumination conditions, including limited outdoor scenarios. Quantitative tests demonstrate that the reflectance can be estimated correctly to within a few percent even in cases with severe un-even ambient illumination.
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