disadvantages of graphical representation of data

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From Wikipedia

Visualization (computer graphics) - Wikipedia, the free encyclopedia

As a subject in computer science, data visualization or scientific visualization is the use of interactive, sensory representations, typically visual, ...

3D computer graphics - Wikipedia, the free encyclopedia

3D computer graphics (in contrast to 2D computer graphics) are graphics that use a three-dimensional representation of geometric data (often Cartesian) that ...

3D modeling

In 3D computer graphics, 3D modeling (also known as meshing) is the process of developing a mathematical representation of any three-dimensionalsurface of object (either inanimate or living) via specialized software. The product is called a 3D model. It can be displayed as a two-dimensional image through a process called 3D renderingor used in acomputersimulation of physical phenomena. The model can also be physically created using 3D Printing devices.

Models may be created automatically or manually. The manual modeling process of preparing geometric data for 3D computer graphics is similar to plastic arts such as sculpting.

Models

3D models represent a 3D object using a collection of points in 3D space, connected by various geometric entities such as triangles, lines, curved surfaces, etc. Being a collection of data (points and other information), 3D models can be created by hand, algorithmically (procedural modeling), or scanned.

3D models are widely used anywhere in 3D graphics. Actually, their use predates the widespread use of 3D graphics on personal computers. Many computer games used pre-rendered images of 3D models as sprites before computers could render them in real-time.

Today, 3D models are used in a wide variety of fields. The medical industry uses detailed models of organs. The movie industry uses them as characters and objects for animated and real-life motion pictures. The video game industry uses them as assets for computer and video games. The science sector uses them as highly detailed models of chemical compounds. The architecture industry uses them to demonstrate proposed buildings and landscapes through Software Architectural Models. The engineering community uses them as designs of new devices, vehicles and structures as well as a host of other uses. In recent decades the earth science community has started to construct 3D geological models as a standard practice.

Representation

Almost all 3D models can be divided into two categories.

  • Solid - These models define the volume of the object they represent (like a rock). These are more realistic, but more difficult to build. Solid models are mostly used for nonvisual simulations such as medical and engineering simulations, for CAD and specialized visual applications such as ray tracing and constructive solid geometry
  • Shell/boundary - these models represent the surface, e.g. the boundary of the object, not its volume (like an infinitesimally thin eggshell). These are easier to work with than solid models. Almost all visual models used in games and film are shell models.

Because the appearance of an object depends largely on the exterior of the object, boundary representations are common in computer graphics. Two dimensional surfaces are a good analogy for the objects used in graphics, though quite often these objects are non-manifold. Since surfaces are not finite, a discrete digital approximation is required: polygonal meshes (and to a lesser extent subdivision surfaces) are by far the most common representation, although point-based representations have been gaining some popularity in recent years. Level sets are a useful representation for deforming surfaces which undergo many topological changes such as fluids.

The process of transforming representations of objects, such as the middle point coordinate of a sphere and a point on its circumference into a polygon representation of a sphere, is called tessellation. This step is used in polygon-based rendering, where objects are broken down from abstract representations ("primitives") such as spheres, cones etc., to so-called meshes, which are nets of interconnected triangles. Meshes of triangles (instead of e.g. squares) are popular as they have proven to be easy to render using scanline rendering. Polygon representations are not used in all rendering techniques, and in these cases the tessellation step is not included in the transition from abstract representation to rendered scene.

Modeling processes

There are five popular ways to represent a model:

  • Polygonal modeling - Points in 3D space, called vertices, are connected by line segments to form a polygonal mesh. Used, for example, by Blender. The vast majority of 3D models today are built as textured polygonal models, because they are flexible and because computers can render them so quickly. However, polygons are planar and can only approximate curved surfaces using many polygons.
  • NURBS modeling - NURBS Surfaces are defined by spline curves, which are influenced by weighted control points. The curve follows (but does not necessarily interpolate) the points. Increasing the weight for a po


From Yahoo Answers

Question:I heard all the advantage of graphic representation of equation. what are the disadvantage of it?

Answers:limited range and limited accuracy. If you graph y = x on graph paper where x runs between 10 and +10, then the value of y cannot be determined if x = 11. Furthermore, the accuracy is limited to the resolution of the graph paper. So you could read y = 4.02 for x = 2 One more disadvantage: difficult to read, need training on how to read graphs. And another, graph paper is fragile, some water and your graph is gone. And another: you can't email it. .

Question:A network administrator has been asked to provide a graphic representation of exactly where the company network wiring and equipment are located in the building. What is this type of drawing? logical topology physical topology cable path wiring grid access topology

Answers:This sounds like a physical topology, though us network admins don't use this terminology in our day-to-day. I usually call it a physical map. Logical topology drawings contain less-than-exact physical mappings but precise IP and routing protocol information for the internal network. Cable paths are physical maps for major cable runs between patch panels, data centers, core network devices, etc. Wiring grids are usually electrical diagrams, and network admins are usually only interested in locations of major sources of EMI (electro-magnetic interference.) Access topologies are physical and logical of all entry points into your network, including provider MPOEs (major points of entry), location/equipage of COs (central offices), etc.

Question:The geometric transformation stage maps triangles from a 3D coordinate system (object space) to a 2D coordinate system (image space) by performing a series of transformations. The computation in this stage is mostly floating-point intensive, involving linear algebraic operations such as matrix multiplication and dot products. The rasterization stage converts transformed triangles into pixel values to be shown on the computer screen. This stage involves mostly integer arithmetic, such as simple additions and comparisons. Unlike rasterization stage, geometric transformation stage is continuous, performed on the geometric definition of objects, but its input is not adequate for sampled digital images. Raster graphics provides the capability to present realistic, shaded, and textured surfaces in full color, as well as line drawings. It is adequate for sampled digital images. The main disadvantages of this rasterization stage are the aliasing present in the image due to the discrete nature of the representation, and the large memory and processing power this stage requires. The input of the geometric transformation stage cannot provide the ideal environment for mixing digital images with synthetic graphics. Why not? What's missing? Or, what's not in the ideal form?

Answers:Well the question isn't very clear, but basically, transformations are only done on vertices. There is no indication of color, only locations of objects and their enpoints. The vertices are the "input" for transformations. Rasterization, considers color and meshes, however, it processes them according to an algorithm. Depending on the sophistication of the hardware being used, the quality of the results can vary widely, but can still have certain aliasing effects etc, as mentioned. Taking an image that is generated in that way can't have the natural touch that comes from digital images created by a person, or taken from a camera. The exception might be for a program that was specifically created for this task (i.e. to humanize the rasterization process, which has been done, but not in real-time systems to my knowledge). So this is why mixing natural images with synthetic rasterizations will have problems...because the algorithms in the synthetic environment spoil the "naturalness" of the image.

Question:Also, Out of: Stem and leaf Box & whisker Histograms Cumulative freq. graphs What are suitable ways of presenting raw data for a sample situation...

Answers:Stem and leaf diagrams record data values in rows, and can easily be made into a histogram. Large data sets can be accomodated by splitting stems. Advantages: - Concise representation of data - Shows range, minimum & maximum, gaps & clusters, and outliers easily - Can handle extremely large data sets Disadvantages: - Not visually appealing - Does not easily indicate measures of centrality for large data sets Pictogram,line graph,pie chart,bar graph and scatterplot are normally classified as 'data handling' ways.

From Youtube

Morphable Face: Automatic 3D Reconstruction and Manipulation from Single Data-Set Reference Face :www.mpi-inf.mpg.de The Morphable Face Model captures the variations of 3D shape and texture that occur among human faces. It represents each face by a set of model coefficients, and generates new, natural-looking faces from any novel set of coefficients, which is useful in a wide range of applications in computer vision and computer graphics. The Morphable Face Model is derived from a data set of 3D face models by automatically establishing point-to-point correspondence between the examples, and transforming their shapes and textures into a vector space representation. New faces and expressions can be modeled by forming linear combinations of the prototypes. In this framework, it is easy to control complex facial attributes, such as gender, attractiveness, body weight, or facial expressions. Attributes are automatically learned from a set of faces rated by the user, and can then be applied to classify and manipulate new faces. Given a single photograph of a face, we can estimate its 3D shape, its orientation in space and the illumination conditions in the scene. Starting from a rough estimate of size, orientation and illumination, our algorithm optimizes these parameters along with the face's internal shape and surface colour to find the best match to the input image. The face model extracted from the image can be rotated and manipulated in 3D. Matching a morphable model automatically to a single sample image of a face produces a 3D shape and a texture map estimate. The ...

PhotoTechEDU Day 11: Document Image Analysis with Leptonica :Google Tech Talks April 4, 2007 ABSTRACT Graphics typically takes a representation of an image or scene and renders it in raster form. This normally occurs through a well-specified process. What happens when you try to go the other way, from a raster image to a description of its contents? The process, so easy for humans, is not easy for machines, because the input raster data can be highly variable and the interpretation of the contents somewhat arbitrary. We'll talk about how this 'inverse graphics' process can be accomplished quickly and usually with sufficient accuracy for most applications, using rasters of document images as input. The 'trick' is to use the image as the primary...