دانلود رایگان مقاله مدل ساخته شده پارامتری نسل سبک های پیچیده محاسبات نقطه ای

Abstract

This paper presents a novel semi-automated method for the generation of 3D parametric as-built models from point clouds. Laser scanning and photogrammetry have a primary role in the survey of existing facilities, especially for the generation of accurate and detailed as-built parametric models that reflect the true condition of a building. Various studies demonstrate that point clouds have a sporadic adoption in large and complex parametric modeling projects. The lack of advanced processing algorithms able to convert point clouds into parametric objects makes the generation of accurate as-built models a challenging task for irregular elements without predefined shape. The proposed semi-automated method allows the creation of parametric models from photogrammetric and laser scanning point clouds. The method is intended as a multi-step process where NURBS curves and surfaces are used to reconstruct complex and irregular objects, without excessive simplification of the information encapsulated into huge point clouds to avoid heavy models useless for practical purposes and productive work. Different case studies derived from actual BIM-based projects are illustrated and discussed to demonstrate advantages and limitations of the method.

5. Conclusions

This paper presented a methodology for the generation of asbuilt parametric models from dense point clouds able to reveal the actual shape of existing constructions. Starting from a set of registered point clouds, NURBS curves that form a rigid curve network were extracted in a semi-automated way by considering the logic of construction of the building. Then, NURBS surfaces driven by both network and point cloud were generated to reconstruct the shape of complex objects along with their geometric anomalies. As NURBS are mathematical functions defined by numerical coefficients, a rigorous mathematical parametrization becomes feasible and allows the creation of parametric objects. The kind of parametrization shown in this work is optimal for constructive elements that require thickness parametrization with multiple layers.