International Journal of Computer Trends and Technology- volume3Issue1- 2012 ISSN: 2231-2803 http://www.internationaljournalssrg.org Page 18 A Overview of Point-based Rendering Techniques Mandakini Kaushik, Kapil Kumar Nagwanshi Dr. Lokesh Kumar Sharma M.Tech.(CSE) Scholar, Dept. of CSE, Reader , Dept. of CSE, Head, Dept. of CSE, Rungta College of Engg. & Tech., Rungta College of Engg. & Tech., Rungta College of Engg. & Tech., Bhilai – 490 024(C.G.), INDIA Bhilai – 490 024(C.G.), INDIA Bhilai – 490 024(C.G.), INDIA Abstract— In recent years point-based geometry has gained increasing attention as an alternative surface representation, both for efficient rendering and for flexible geometry processing of highly complex 3D-models. Traditional geometry based rendering methods use triangles as primitives which make rendering complexity dependent on complexity of the model to be rendered. But point based models overcome that problem as points don't maintain connectivity information and just represents surface information. Based on their fundamental simplicity, points have motivated a variety of research on topics such as shape modeling, object capturing, simplification, rendering and hybrid point-polygon methods. Rendering the points is inherently a big problem due to lack of connectivity information. But lack of connectivity introduces several artifacts while in the process of rendering like aliasing and holes in the rendered model. Several algorithms have been proposed for rendering point models efficiently and with high quality. The major challenge of point-based rendering (PBR) algorithms is to achieve a continuous interpolation between discrete point samples that are irregularly distributed on a surface. Furthermore, correct visibility must be supported as well as efficient level-of-detail (LOD) rendering for large data sets. Our work has the basis of understanding of the various popular algorithms for point rendering like qsplat and elliptical weighted average splatting. We will discuss advantages and disadvantages of each of the approaches and we will define and compare the result of all various algorithms. Keywords- computer graphics, point based rendering, qsplat, surfel, surface splatting, randomized Z-buffer algirithm I. INTRODUCTION Rendering is the process of generating an image from a model by means of a software program. The model is a description of three dimensional objects in a strictly defined data structure. It contains geometry, viewpoint, texture and lighting information. Rendering is one of the major field of 3D computer graphics. In the graphics pipeline it’s the last major step, giving the final appearance to the models and animation. With the increasing sophistication of computer graphics since the 1970s onward, it has become a more distinct subject. It has uses in computer and video games, simulators, movies or TV special effects, and design visualization, each employing a different balance of features and techniques. As a product, a wide variety of renderers are available. some are integrated into larger modeling and animation packages, some are stand-alone, some are free open-source projects. On the inside, a renderer is a carefully engineered program, based on a selective mixture of disciplines related to light physics, visual perception, mathematics, and software development. In rendering, a modeling primitive (an object representation) and a rendering primitive are different issues. An object can be stored in one format, and converted into another one for rendering. An example of this is parametric patches, which are tessellated into triangles for rendering. On the other hand, many representations, such as points and polygon meshes, can be rendered directly. We can distinguish two fundamental approaches to rendering: geometry-based and image-based rendering. • In geometry-based rendering, a scene is described using geometrical primitives, which are discretized into points, lines and triangles for rendering. • In image-based rendering, a scene is rendered making use of multiple input images, without any 3D object or scene information. Most rendering algorithms are a combination of these two paradigms, for example texture mapping (image-based) in polygon rendering (geometry-based). II. POINT AS OVERVIEW OF RENDERING A. rendering premitives In the world of computer graphics, rendered images are represented by a collection of objects. These objects are often composite, constructed from a number of more basic primitive objects. Typically these primitives have been based on volumes (Constructive Solid Geometry) or manifold representations (splines, polygons). Although these methods are good for large objects of reasonable complexity, they become somewhat inefficient at representing objects with high levels of detail (LOD). Recently another type of primitive has been introduced, which uses points. Using points as the rendering primitive, output images are constructed from a cloud of points and this is known as Point-Based Rendering (PBR). Comparing polygon meshes with points is analogous to comparing vector graphics with pixel graphics. Points in 3D are analogous to pixels in 2D, replacing textured triangles or higher order surfaces by zero-dimensional elements. Thus point based rendering is a geometry based rendering method inspired by the image based rendering techniques whose rendering method is output sensitive. Point sample rendering can be done in two different approaches, point