POLYFIT ASSISTED MONOSCOPIC MULTI-IMAGE MEASUREMENT SYSTEMS

Nowadays, in light of the latest development in three-dimensional (3D) modeling technology, an essential role is given to the research and development of fully-automated or semi-automated processes in order to increase workflow effectiveness. A key challenge is thus to automate the process leading to the geometric model which supports the Building Information Modeling (BIM) or 3D-Geographical Information Systems (3D-GIS). This 3D model usually originates from image-based or range-based point clouds. This research is the beginning of the development of a 3D modeling approach that is semi-automatic, and possibly fully-automatic, by combining polygon surface fitting (polyfit) technique and monoscopic multi-image measurement system. With the advent of dense matching and Structure from Motion methods (SfM), point clouds can be generated from multiple images obtained from digital cameras. Then, to reduce the data and to allow for efficient processing, it is necessary to extract polygonal surface data from point clouds delivered by the dense matching process. The polygonal surface is then used for the basis of further manual monoscopic measurements which are achieved separately on each image to obtain more detailed 3D model. Next, this approach analyzed the polygonal surface deformations in comparison to the initial point cloud data. It can be seen how the resolution and noise of the original point clouds affect the subsequent Polyfit-based modeling and monoscopic measurements. The deformations and the accuracy evaluation have been undertaken using different open source software. Also, the geometric error in the polyfit-derived polyhedral reconstruction propagating to the subsequent monoscopic-derived measurements was evaluated. Finally, our modeling approach shows that it can improve the processing speed and level of detail of the 3D models achieved using existing monoscopic measurements. Typically geometric accuracy itself doesn’t have enough information to make accurate geometry model.

Fast tetrahedral mesh generation and segmentation of an atlas-based heart model using a periodic uniform grid

A fast procedure for generation of regular tetrahedral finite element mesh for objects with complex shape cavities is proposed. The procedure like LBIE-Mesher can generate tetrahedral meshes for the volume interior to a polygonal surface, or for an interval volume between two surfaces having a complex shape and defined in STL-format. This procedure consists of several stages: generation of a regular tetrahedral mesh that fills the volume of the required object; generation of clipping for the uniform grid parts by a boundary surface; shifting vertices of the boundary layer to align onto the surface.We present a sequential and parallel implementation of the algorithm and compare their performance with existing generators of tetrahedral grids such as TetGen, NETGEN, and CGAL. The current version of the algorithm using the mobile GPU is about 5 times faster than NETGEN. The source code of the developed software is available on GitHub.

Geometric Parameters of Cutting Tools that Can be Used for Forming Sided Surfaces with Variable Profile

This article describes machining technology of polyhedral surfaces with varying profile, which is provided by planetary motion of multiblade block tools. The features of the technology and urgency of the problem is indicated. The purpose of the study is to determine the minimum value of the clearance angle of the tool. Also, the study is carried out about changing the value of the front and rear corners during the formation of polygonal surface using a planetary gear. The scheme of calculating the impact of various factors on the value of the minimum clearance angle of the tool and kinematic front and rear corners of the instrument is provided. The mathematical formula for calculating the minimum clearance angle of the tool is given. Also, given the formula for determining the front and rear corners of the tool during driving. This study can be used in the calculation of the design operations forming multifaceted external surfaces with a variable profile by using the planetary gear.

Bump mapping effect application analysing

Bump mapping is an easy way to create the effect of the relief surface that allows a more detailed surface than a polygonal surface does. If there are bumps in surface, you can see light and dark place on surface. Flat surfaces reflect more light and bumpy surfaces reflect less. This effect is used in bump technology. OpenGL, WebGL and DirectX supports this bump technology. This realization is not difficult and is working fast. This is an implementation in pixel or fragment shader.

Polyhedra faster than spheres?

Purpose – The purpose of this paper is to present a new and efficient technique for discrete element modelling using non-convex polyhedral grain shapes. Design/methodology/approach – The efficiency of the technique follows from the use of grains that are dilated versions of the basic polyhedral grain shapes. Dilation of an arbitrary polyhedral grain is accomplished by placing the center of a sphere of fixed radius at every point on the surface. The dilated vertices become sphere segments and the edges become cylinder segments. The sharpness of the vertices and edges can be adjusted by varying the dilation radius. Contacts between two dilated polyhedral grains can be grouped into three categories; vertex on surface, vertex on edge, and edge on edge, or in the grammar of the model, sphere on polygonal surface, sphere on cylinder, and cylinder on cylinder. Simple, closed-form solutions exist for each of these cases. Findings – The speed of the proposed polyhedral discrete element model is compared to similar models using spherical and ellipsoidal grains. The polyhedral code is found to run about 40 percent as fast as an equivalent code using spherical grains and about 80 percent as fast as an equivalent code using ellipsoidal grains. Finally, several applications of the polyhedral model are illustrated. Originality/value – Few examples of discrete element modeling studies in the literature use polyhedral grains. This dearth is because of the perceived complexity of the polyhedral coding challenges and the slow speed of the codes compared to codes for other grain shapes. This paper presents a much simpler approach to discrete element modeling using polyhedral grain shapes.