Product design efficiency: surface vs. voxel modeling - Lead time and surface quality
0
Citation
0
Reference
20
Related Paper
Abstract:
Product design tend to keep surface modelling as a major means for creating geometry, where excessive time is spent and specialized professions are needed sometimes. Would a change to voxel modelling increase efficiency without reducing surface quality? A comparison between software for surface modeling and voxel modeling was made. Two objects were modeled side-by-side in the two software, one motorcycle tank demanding high surface quality and one automotive seat having detailed form. Surface quality was evaluated using curvature visualization and lead time from sketch to finished CAD object was measured. The tests showed voxel modeling to be much faster than surface modeling for both objects significant difference. However, there was a difference in surface smoothness in favor of surface modeling, although not visible in real-time rendered reflections. Despite the quality difference, voxel modeling might be accurate enough even for products with glossy surfaces, such as automotive exterior panels.Keywords:
Sketch
3D modeling
Solid modeling
Smoothness
Cite
Interpolation
Surface reconstruction
Spline (mechanical)
Cite
Citations (37)
In recent years, the elements reconstruction based on existing physical objects, plays an increasingly important role in research and everyday life. With the advancement of modern industry, more and more often reverse engineering is used, including automotive industry, modeling and deformation techniques of the objects. One of such example is the reconstruction of the geometry of motor vehicles using 3D scans. Damages of motor vehicles cause local changes in the shape of the product and their size and character is directly related to the occurred reaction. However, to assess the damage extent and qualify the object for further repair, it is necessary to thoroughly know the condition of the object after the damage to select the appropriate technology and repair method. This is the case for reverse engineering, and 3D scanning using structural light. The aim of the study was to evaluate the influence of the parameters of the 3D scanner on the accuracy of reconstructing the geometry of the vehicle element – the rear door of the Skoda Octavia in two variants, non-deformed and deformed. The dimensions of door exceeded the range of the largest single measuring area of used 3D scanner, so it was necessary to use the photogrammetric technique in order to generate a point model of the object that was used to compose the individual scans. Parameters of 3D scanner has significant effect on obtained results – in case of scanning small objects by big measuring field, discontinuities and unscanned areas can occur. For large objects any measuring volume can be used, but increased resolution do not increase accuracy every time, and results depends on environment conditions, object surface preparation and skills of the operator.
Reverse engineering
Classification of discontinuities
3D Scanning
Laser Scanning
Structured-light 3D scanner
Cite
Citations (2)
SUMMARY A main advantage of terrestrial laser scanning is the possibility to nearly simultaneously acquire the geometrical positions of millions of object points in 3D. However this is also the main bottle neck of terrestrial laser scanning when it comes to data processing. In this paper a new strategy will be proposed, presented and applied in order to show how to overcome the discrepancies. The modelling and processing will be done based on surface parameters which will be efficiently derived from point cloud measurements. It will be shown, that there is no need for a triangularisation of the points prior to a derivation of significant surface parameters. In such a way enormous data reduction will be achieved. It becomes feasible to combine adjacent scans completely based on identical surface parameters derived from natural objects detected automatically in both scans. Natural objects may be used for geo-referencing as well. Characteristic lines can be derived from the intersection of surfaces. Due to the high point density of the scan, an increased improvement of the accuracy of the surface parameters will be achieved even for small extensions of the detected surfaces. Then even deformation analysis of walls of buildings can be based on surface parameters. From the surface parameters and a defined boundary line and boundary plane also the volume under the surface can be easily determined. Examples from rail monitoring, building monitoring and the automatic determination of the volume of a pile of coal are presented in order to demonstrate the efficiency of the concept.
Laser Scanning
Data Processing
Cite
Citations (1)
For the construction of breakwaters large amounts of armourstone which are produced in dedicated quarries are needed. The better the in-situ block size distribution (IBSD) of these quarries can be determined, the more accurately the quarry production can be predicted. Currently, the IBSD prediction is based on manually acquired scanline data. This method is accompanied with a lot of disadvantages as it is an unsafe, time consuming and subjective method of data gathering in which the amount of gathered data strongly depends on the reach of the surveyor. To determine the IBSD the resulting data is inserted into Wang’s equation method, which uses the mean discontinuity set properties (orientation and principal mean spacing) as input. Taking the disadvantages of the manual scanlining method into account, 3D terrestrial laser scanning is proposed as a suitable alternative to gather the discontinuity data. This thesis investigates the applicability of laser data for IBSD determination. The research is based on the manual and laser data that was gathered during a fieldwork in the Dan-quarry in Benin. Firstly, it is investigated whether it is possible to replace the manually gathered discontinuity data by laser data by simulating a virtual scanline in the point cloud. Secondly, as the laser scanner allows to gather discontinuity data across the entire rockface, an alternative method which allows to take all the obtained discontinuity data directly into account becomes necessary. It is for this purpose that the voxel method in this thesis is developed. This approach has not been used for geotechnical purposes before and is based on the method that is used in the medical world to determine volume data from CT scans. It requires a bounding box to be subdivided into voxels of a predefined size. The position of the centre of each voxel is evaluated with respect to all discontinuity planes that intersect the bounding box. As voxels with the same position with respect to all discontinuity planes can be considered to belong to the same block, the sum of the volumes of these voxels gives the in-situ block size. When comparing the results of the two developed methods with the manually obtained results, it is found that they can represent at best a lower boundary of the IBSD. The main reason for this is that the laser data results in a lot more planes than the manual data. This decreases the IBSD drastically and allows to the conclude that although the orientation data can be easily obtained from the laser data, more effort is needed to obtain the correct spacing and the persistence of the found discontinuities. The effects caused by this are larger in case of the voxel method as all discontinuities over the full height of the face are taken into account instead of only the ones that intersect the virtual scanline. Therefore it is concluded that the virtual scanline method can be used to determine a lower boundary for the IBSD whereas the voxel method, although it has great potential to become an alternative method for IBSD determination from laser scan data, needs more research.
Discontinuity (linguistics)
Laser Scanning
Scan line
Data set
Data Processing
Cite
Citations (0)
Subroutine
Line (geometry)
Surface reconstruction
Cite
Citations (9)