Quantitative assessment of automatic reconstructions of branching systems

ISBN 978-951-651-408-9International audienceIn this work, we propose a method to evaluate and compare different reconstruction methods from laser data using expert reconstruction and a new structural distance

Influence of point cloud density on the results of automated Object-Based building extraction from ALS data

Ponencias, comunicaciones y pósters presentados en el 17th AGILE Conference on Geographic Information Science "Connecting a Digital Europe through Location and Place", celebrado en la Universitat Jaume I del 3 al 6 de junio de 2014.Nowadays there is a plethora of approaches dealing with object extraction from remote sensing data. Airborne Laser scanning (ALS) has become a new method for timely and accurate collection of spatial data in the form of point clouds which can vary in density from less than one point per square meter (ppsm) up to in excess of 200 ppsm. Many algorithms have been developed which provide solutions to object extraction from 3D data sources as ALS point clouds. This paper evaluates the influence of the spatial point density within the point cloud on the obtained results from a pre-developed Object-Based rule set which incorporates formalized knowledge for extraction of 2D building outlines. Analysis is performed with regards to the accuracy and completeness of the resultant extraction dataset. A pre-existing building footprint dataset representing Lake Tahoe (USA) was used for ground truthing. Point cloud datasets with varying densities (18, 16, 9, 7, 5, 2, 1 and 0.5ppsm) where used in the analysis process. Results indicate that using higher density point clouds increases the level of classification accuracy in terms of both completeness and correctness. As the density of points is lowered the accuracy of the results also decreases, although little difference is seen in the interval of 5-16ppsm

Rendering of Wind Effects in 3D Landscape Scenes

AbstractVisualization of 3D landscape scenes is often used in architectural modeling systems, realistic simulators, computer virtual reality, and other applications. Wind is a common spread natural effect without which any scene would be unrealistic. Three algorithms for tree rendering under changeable wind parameters were developed. They have a minimal computational cost and simulate weak wind; mid-force wind, and storm wind. A 3D landscape scene is formed from a set of trees models that are generated from laser data and templates of L-systems. The user can tune the wind parameters and manipulate a modeling scene by using the designed software tool

Comparative analysis of technologies and methods for automatic construction of building information models for existing buildings

Building Information Modelling (BIM) provides an intelligent and parametric digital platform to support activities throughout the life-cycle of a building and has been used for new building construction projects nowadays. However, most existing buildings today do not have complete as-built information documents after the construction phase, nor existed meaningful BIM models. Despite the growing use of BIM models and the improvement in as-built records, missing or incomplete building information is still one of the main reasons for the low-level efficiency of building project management. Furthermore, as-built BIM modelling for existing buildings is considered to be a time-consuming process in real projects. Researchers have paid attention to systems and technologies for automated creation of as-built BIM models, but no system has achieved full automation yet. With the ultimate goal of developing a fully automated BIM model creation system, this paper summarises the state-of-the-art techniques and methods for creating as-built BIM models as the starting point, which include data capturing technologies, data processing technologies, object recognition approaches and creating as-built BIM models. Merits and limitations of each technology and method are evaluated based on intensive literature review. This paper also discusses key challenges and gaps remained unaddressed, which are identified through comparative analysis of technologies and methods currently available to support fully automated creation of as-built BIM models.published_or_final_versio

Modelling and Simulation of Lily flowers using PDE Surfaces

This paper presents a partial differential equation (PDE)-based surface modelling and simulation framework for lily flowers. We use a PDE-based surface modelling technique to represent shape of a lily flower and PDE-based dynamic simulation to animate blossom and decay processes of lily flowers. To this aim, we first automatically construct the geometry of lily flowers from photos to obtain feature curves. Second, we apply a PDE-based surface modelling technique to generate sweeping surfaces to obtain geometric models of the flowers. Then, we use a physics-driven and data-based method and introduce the flower shapes at the initial and final positions into our proposed dynamic deformation model to generate a realistic deformation of flower blossom and decay. The results demonstrate that our proposed technique can create realistic flower models and their movements and shape changes against time efficiently with a small data size