دانلود رایگان مقاله بازرسی تعاملی چند شی پیچیده اسمبلی صنعتی

Abstract

The use of virtual prototypes and digital models containing thousands of individual objects is commonplace in complex industrial applications like the cooperative design of huge ships. Designers are interested in selecting and editing specific sets of objects during the interactive inspection sessions. This is however not supported by standard visualization systems for huge models. In this paper we discuss in detail the concept of rendering front in multiresolution trees, their properties and the algorithms that construct the hierarchy and efficiently render it, applied to very complex CAD models, so that the model structure and the identities of objects are preserved. We also propose an algorithm for the interactive inspection of huge models which uses a rendering budget and supports selection of individual objects and sets of objects, displacement of the selected objects and real-time collision detection during these displacements. Our solution–based on the analysis of several existing view-dependent visualization schemes–uses a Hybrid Multiresolution Tree that mixes layers of exact geometry, simplified models and impostors, together with a time-critical, view-dependent algorithm and a Constrained Front. The algorithm has been successfully tested in real industrial environments; the models involved are presented and discussed in the paper.

8. Conclusions and future work

The paper contributes to the field by proposing a formalization of the front concept and a new object-aware algorithm for the interactive inspection of huge models which uses a rendering budget and supports selection of individual objects and sets of objects, displacement of the selected objects and real-time collision detection during these displacements. As far as we know, no present algorithm addresses rendering such huge sets of objects with guaranteed frame rates, while allowing for the modification of individual objects during the inspection and attempting to optimize image quality. Our proposal addresses these needs, and is also able to verify on the fly possible collisions when moving objects around. The proposed algorithm has proved to successfully solve a precise need in the design of huge assemblies and is now being used in real ship design environments. In our tests, we have not perceived differences between the quality of the images rendered by our algorithm with respect to the ground truth represented by the input models. Isolated frames may present transient artifacts when the visibility changes abruptly, since the updates exceed the budget, but they very quickly disappear. Although we have not discussed it here, our current implementation supports textured polygons and selection through attributes. To be able to fully support textured models, however, we need to further improve the ORIs to handle them. This is intended as future work. Because of the locality in space afforded by the Kd-trees, the whole pre-processing is amenable to being done out-of-core, and hence our approach should scale well for even larger models and modest hardware. Another avenue of improvement is therefore the implementation of this out-of-core approach in a fully automatic way.