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Encyclopedia > Normal mapping
Normal mapping used to re-detail simplified meshes.
Normal mapping used to re-detail simplified meshes.

In 3D computer graphics, normal mapping is an application of the technique known as bump mapping. Normal mapping is sometimes referred to as "Dot3 bump mapping". While bump mapping perturbs the existing normal (the way the surface is facing) of a model, normal mapping replaces the normal entirely. Like bump mapping, it is used to add details to shading without using more polygons. But where a bump map is usually calculated based on a single-channel (interpreted as grayscale) image, the source for the normals in normal mapping is usually a multichannel image (that is, channels for "red", "green" and "blue" as opposed to just a single color) derived from a set of more detailed versions of the objects. The values of each channel (color) usually represent the xyz coordinates of the normal in the point corresponding to that texel. Image File history File links Download high resolution version (963x543, 286 KB)Example of normal mapping for recreating the details lost during a drastic simplification File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Image File history File links Download high resolution version (963x543, 286 KB)Example of normal mapping for recreating the details lost during a drastic simplification File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... 3D computer graphics are different from 2D computer graphics in that a three-dimensional representation of geometric data is stored in the computer for the purposes of performing calculations and rendering 2D images. ... A sphere without bump mapping. ... Shading refers to depicting depth in 3D models by varying levels of darkness. ... In 3D computer graphics, polygonal modeling is an approach for modeling objects by representing or approximating their surfaces using polygons. ... In computing, a grayscale or greyscale digital image is an image in which the value of each pixel is a single sample. ...


Normal mapping is usually found in two varieties: object-space and tangent-space normal mapping. They differ in coordinate systems in which the normals are measured and stored.


One of the most interesting uses of this technique is to greatly enhance the appearance of a low poly model exploiting a normal map coming from a high resolution model. While this idea of taking geometric details from a high resolution model had been introduced in "Fitting Smooth Surfaces to Dense Polygon Meshes" by Krishnamurthy and Levoy, Proc. SIGGRAPH 1996, where this approach was used for creating displacement maps over nurbs, its application to more common triangle meshes came later. In 1998 two papers were presented with the idea of transferring details as normal maps from high to low poly meshes: "Appearance Preserving Simplification", by Cohen et al. SIGGRAPH 1998, and "A general method for recovering attribute values on simplified meshes" by Cignoni et al. IEEE Visualization '98. The former presented a particular constrained simplification algorithm that during the simplification process tracks how the lost details should be mapped over the simplified mesh. The latter presented a simpler approach that decouples the high and low polygonal mesh and allows the recreation of the lost details in a way that is not dependent on how the low model was created. This latter approach (with some minor variations) is still the one used by most of the currently available tools. Low poly is a term used by videogame creators, players and journalists alike to describe a three-dimensional computer generated character or object that appears to be lacking in polygons. ... SIGGRAPH 2005 official logo SIGGRAPH (short for Special Interest Group in Graphics) is the name of the annual conference on computer graphics convened by the ACM SIGGRAPH organization. ... It has been suggested that this article or section be merged with Displacement map. ... NURBS, short for nonuniform rational B-spline, is a computer graphics technique for drawing curves. ...

Contents

How it works

To calculate the Lambertian (diffuse) lighting of a surface, the unit vector from the shading point to the light source is dotted with the unit vector normal to that surface, and the result is the intensity of the light on that surface. Many other lighting models also involve some sort of dot product with the normal vector. Imagine a polygonal model of a sphere - you can only approximate the shape of the surface. By using an RGB bitmap textured across the model, more detailed normal vector information can be encoded. Each color channel in the bitmap (red, green and blue) corresponds to a spatial dimension (X, Y and Z). These spatial dimensions are relative to a constant coordinate system for object-space normal maps, or to a smoothly varying coordinate system (based on the derivatives of position with respect to texture coordinates) in the case of tangent-space normal maps. This adds much more detail to the surface of a model, especially in conjunction with advanced lighting techniques. If a surface exhibits Lambertian reflectance, light falling on it is scattered such that the amount of light an observer sees, the surface luminance, is the same regardless of their angle of view. ... A vector going from A to B. In physics and in vector calculus, a spatial vector, or simply vector, is a concept characterized by a magnitude and a direction. ... In mathematics, the dot product, also known as the scalar product, is a binary operation which takes two vectors over the real numbers R and returns a real-valued scalar quantity. ... REDIRECT RGB color model ...


In the most common implementation of normalmaps, used by Valve's Source engine and implemented in hardware in nVidia cards, the red channel should be the relief of the material when lit from the right, the green channel should be the relief of the material when lit from below, and the blue channel should be the relief of the material when lit from the front(practically, full except on the "slopes"); or, to put it another way, the XYZ coordinates of the face normals are placed in the RGB values of the normal map. If a material is classified as being reflective, the albedo is usually encoded in the alpha channel if one exists. Valve Corporation is an American video game developer based in Bellevue, Washington, USA, made famous by its first product, Half-Life, which was released in November 1998. ... Source engine logo A Half-Life 2: Episode One scene running on the Source engine, demonstrating High Dynamic Range, Rim lighting, Phong shading, facial expressions, realtime cameras and VGUI. In-engine Team Fortress 2 character line-up, demonstrating a cartoon-oriented set of basic shaders, depth of field, facial animation... Albedo is the ratio of reflected to incident electromagnetic radiation. ...


Normal mapping in videogames

Interactive normal map rendering was originally only possible on PixelFlow, a parallel graphics machine built at the University of North Carolina at Chapel Hill. It was later possible to perform normal mapping on high-end SGI workstations using multi-pass rendering and frame buffer operations or on low end PC hardware with some tricks using paletted textures. However, with the advent of shaders in home PCs and gaming consoles, normal mapping became widely used in videogames starting in 2004, and followed by open source games in later years. Normal mapping's popularity for real-time rendering is due to its good quality to processing requirements ratio versus other methods of producing similar effects. Much of this efficiency is made possible by distance-indexed detail scaling, a technique which selectively decreases the detail of the normal map of a given texture (cf. mipmapping), meaning that more distant surfaces require less complex lighting simulation. The University of North Carolina at Chapel Hill is a public, coeducational, research university located in Chapel Hill, North Carolina, United States. ... Silicon Graphics, Inc. ... Shaders are a set of different technologies. ... shelby was here 2004 (MMIV) was a leap year starting on Thursday of the Gregorian calendar. ... In 3D computer graphics texture mapping, MIP maps (also mipmaps) are pre-calculated, optimized collections of bitmap images that accompany a main texture, intended to increase rendering speed and reduce artifacts. ...


Microsoft's Xbox was the first home game console to support the effect on the GPU (other sixth generation consoles use a CPU-based implementation). Developers on the Xbox 360 and the PlayStation 3 rely heavily on normal mapping and are beginning to implement parallax mapping. The Wii also uses normal mapping. The Xbox is a sixth generation era video game console produced by Microsoft Corporation. ... GPU may stand for: Graphics processing unit, a special stream processor used in computer graphics hardware Gosudarstvennoye Politicheskoye Upravlenie (Главное Политическое Управление, or Main Political Directorate) of the Red Army, responsible for troops morale and propaganda. ... The sixth-generation era (sometimes referred to as the 128-bit era; see Number of bits below) refers to the computer and video games, video game consoles, and video game handhelds available at the turn of the 21st century. ... CPU can stand for: in computing: Central processing unit in journalism: Commonwealth Press Union in law enforcement: Crime prevention unit in software: Critical patch update, a type of software patch distributed by Oracle Corporation in Macleans College is often known as Ash Lim. ... The Xbox 360 is the successor to Microsofts Xbox video game console, developed in cooperation with IBM, ATI, Samsung and SiS. Information on the console first came through viral marketing campaigns and it was officially unveiled on MTV on May 12, 2005, with detailed launch and game information divulged... PlayStation 3 , trademarked PLAYSTATION®3,[7] commonly abbreviated PS3) is Sony Computer Entertainments third video game console. ... Parallax Mapping (also, Photonic Mapping, Offset Mapping or Virtual Displacement Mapping) is an enhancement of the bump mapping or normal mapping techniques applied to textures in 3D rendering applications such as video games. ... The Wii (pronounced as the pronoun we, IPA: ) is the fifth home video game console released by Nintendo. ...


See also

Spherical texture mapping Texture mapping is a method, pioneered by Edwin Catmull, of adding detail, surface texture, or colour to a computer-generated graphic or 3D model. ... A sphere without bump mapping. ... Parallax Mapping (also, Photonic Mapping, Offset Mapping or Virtual Displacement Mapping) is an enhancement of the bump mapping or normal mapping techniques applied to textures in 3D rendering applications such as video games. ... It has been suggested that this article or section be merged with Displacement map. ... Linear algebra is the branch of mathematics concerned with the study of vectors, vector spaces (also called linear spaces), linear maps (also called linear transformations), and systems of linear equations. ...

External links

  • Blender Normal Mapping
  • Normal Mapping with paletted textures using old OpenGL extensions.
  • Normal Map Photography Creating normal maps manually by layering digital photographs

Bibliography


 
 

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