Point Cloud Scanner

A point cloud is a set of data points in some coordinate system.

In a three-dimensional coordinate system, these points are usually defined by X, Y, and Z coordinates, and often are intended to represent the external surface of an object.

Point clouds may be created by 3D scanners. These devices measure a large number of points on an object's surface, and often output a point cloud as a data file. The point cloud represents the set of points that the device has measured.

As the result of a 3D scanning process point clouds are used for many purposes, including to create 3D CAD models for manufactured parts, metrology/quality inspection, and a multitude of visualization, animation, rendering and mass customization applications.

While point clouds can be directly rendered and inspected, usually point clouds themselves are generally not directly usable in most 3D applications, and therefore are usually converted to polygon mesh or triangle mesh models, NURBS surface models, or CAD models through a process commonly referred to as surface reconstruction.

There are many techniques for converting a point cloud to a 3D surface. Some approaches, like Delaunay triangulation, alpha shapes, and ball pivoting, build a network of triangles over the existing vertices of the point cloud, while other approaches convert the point cloud into a volumetric distance field and reconstruct the implicit surface so defined through a marching cubes algorithm.

One application in which point clouds are directly usable is industrial metrology or inspection using industrial computed tomography. The point cloud of a manufactured part can be aligned to a CAD model (or even another point cloud), and compared to check for differences. These differences can be displayed as color maps that give a visual indicator of the deviation between the manufactured part and the CAD model. Geometric dimensions and tolerances can also be extracted directly from the point cloud.

Point clouds can also be used to represent volumetric data used for example in medical imaging. Using point clouds multi-sampling and data compression are achieved.

In geographic information system, point clouds are one of the sources used to make digital elevation model of the terrain. They are also used to generate 3D models of urban environments.

Rebound Hammer Test

                      Rebound hammer test is done to find out the compressive strength of concrete by using rebound hammer as per IS: 13311 (Part 2) – 1992. The underlying principle of the rebound hammer test is

                   The rebound of an elastic mass depends on the hardness of the surface against which its mass strikes. When the plunger of the rebound hammer is pressed against the surface of the concrete, the pring-controlled mass rebounds and the extent of such a rebound depends upon the surface hardness of the concrete. The surface hardness and therefore the rebound is taken to be related to the compressive strength of the concrete. The rebound value is read from a graduated scale and is designated as the rebound number or rebound index. The compressive strength can be read directly from the graph provided on the body of the hammer.

 

Procedure to determine strength of hardened concrete by rebound hammer.

i) Before commencement of a test, the rebound hammer should be tested against the test anvil, to get reliable results, for which the manufacturer of the rebound hammer indicates the range of readings on the anvil suitable for different types of rebound hammer.

ii) Apply light pressure on the plunger – it will release it from the locked position and allow it to extend to the ready position for the test.
iii) Press the plunger against the surface of the concrete, keeping the instrument perpendicular to the test surface. Apply a gradual increase in pressure until the hammer impacts. (Do not touch the button while depressing the plunger. Press the button after impact, in case it is not convenient to note the rebound reading in that position.)
iv) Take the average of about 15 readings.
Interpretation of ResultsThe rebound reading on the indicator scale has been calibrated by the manufacturer of the rebound hammer for horizontal impact, that is, on a vertical surface, to indicate the compressive strength. When used in any other position, appropriate correction as given by the manufacturer is to be taken into account.

Skyscrapers

        A skyscraper is a tall, continuously habitable building of over 40 floors, mostly designed for office, commercial and residential uses. A skyscraper can also be called a high-rise, but the term skyscraper is often used for buildings higher than 150 m (492 ft). For buildings above a height of 300 m (984 ft), the term Supertall can be used, while skyscrapers reaching beyond 600 m (1,969 ft) are classified as Megatall.

           A relatively big building may be considered a skyscraper if it protrudes well above its built environment and changes the overall skyline. The maximum height of structures has progressed historically with building methods and technologies and thus what is today considered a skyscraper is taller than before. The Burj Khalifa is currently the tallest building in the world.

        One common feature of skyscrapers is having a steel framework that supports curtain walls. These curtain walls either bear on the framework below or are suspended from the framework above, rather than load-bearing walls of conventional construction. Some early skyscrapers have a steel frame that enables the construction of load-bearing walls taller than of those made of reinforced concrete. Modern skyscrapers' walls are not load-bearing and most skyscrapers are characterized by large surface areas of windows made possible by the concept of steel frame and curtain walls. However, skyscrapers can have curtain walls that mimic conventional walls and a small surface area of windows. Modern skyscrapers often have a tubular structure, and are designed to act like a hollow cylinder to resist lateral loads (wind, seismic, etc.). To appear more slender, allow less wind exposure, and in order to transmit more daylight to the ground, many skyscrapers have a design with setbacks; sometimes they are also structurally required.

Roof Shapes

Roof shapes differ greatly from region to region. The main factors which influence the shape of roofs are the climate and the materials available for roof structure and the outer covering. Roof terminology is also not rigidly defined. Usages vary slightly from region to region, or from one builder or architect to another.

Roof shapes vary from almost flat to steeply pitched. They can be arched or domed; a single flat sheet or a complex arrangement of slopes, gables and hips; or truncated (terraced, cut) to minimize the overall height.

Types:-

Flat: These are found in traditional buildings in regions with a low precipitation. Modern materials which are highly impermeable to water make possible the very large low-pitch roofs found on large commercial buildings. Although called flat they are generally gently pitched.

Saw-tooth: A roof comprising a mono-pitched roof or for larger buildings, series of, mono-pitched roofs with vertical surfaces glazed and pitched upward in general terms away from the equator, though other directions suit if direct sunlight is desired and where rooftop access may otherwise be impracticable. The roof tops are opaque, shielding traditionally workers and machinery from direct sunlight. This sort of roof commonly admits natural light into a factory, and is also known as "Northlight" in the northern hemisphere implying a single such plane.

Mansard (French roof): A roof with the pitch divided into a shallow slope above a steeper slope. The steep slope may be curved. An element of the Second Empire architectural style (Mansard style) in the U.S.