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Normal mapping

In 3D computer graphics, normal mapping, or “Dot3 bump mapping”, is a technique used for faking the lighting of bumps and dents – an implementation of bump mapping. It is used to add details without using more polygons. A common use of this technique is to greatly enhance the appearance and details of a low polygon model by generating a normal map from a high polygon model or height map.

Normal maps are commonly stored as regular RGB images where the RGB components correspond to the X, Y, and Z coordinates, respectively, of the surface normal.

The idea of taking geometric details from a high polygon model was 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. In 1998, two papers were presented with key ideas for transferring details with normal maps from high to low polygon meshes: “Appearance Preserving Simplification”, by Cohen et al. SIGGRAPH 1998, and “A general method for preserving attribute values on simplified meshes” by Cignoni et al. IEEE Visualization ’98. The former introduced the idea of storing surface normals directly in a texture, rather than displacements, though it required the low-detail model to be generated by a particular constrained simplification algorithm. The latter presented a simpler approach that decouples the high and low polygonal mesh and allows the recreation of any attributes of the high-detail model (color, texture coordinates, displacements, etc.) in a way that is not dependent on how the low-detail model was created waterproof electronics case. The combination of storing normals in a texture, with the more general creation process is still used by most currently available tools.

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. Imagine a polygonal model of a sphere – you can only approximate the shape of the surface. By using a 3-channel bitmap textured across the model, more detailed normal vector information can be encoded. Each channel in the bitmap 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.

Unit Normal vectors corresponding to the u,v texture coordinate are mapped onto normal maps. Only vectors pointing towards the viewer (z: 0 to -1 for Left Handed Orientation) are present, since the vectors on geometries pointing away from the viewer are never shown. The mapping is as follows:

Since a normal will be used in the dot product calculation for the diffuse lighting computation, we can see that the {0, 0, –1} would be remapped to the {128, 128, 255} values, giving that kind of sky blue color seen in normal maps (blue (z) coordinate is perspective (deepness) coordinate and RG-xy flat coordinates on screen). {0.3, 0.4, –0.866} would be remapped to the ({0.3, 0.4, –0.866}/2+{0.5, 0.5, 0.5})*255={0.15+0.5, 0.2+0.5, -0.433+0.5}*255={0.65, 0.7, 0.067}*255={166, 179, 17} values (













{\displaystyle 0.3^{2}+0.4^{2}+(-0.866)^{2}=1}

). The sign of the z-coordinate (blue channel) must be flipped to match the normal map’s normal vector with that of the eye (the viewpoint or camera) or the light vector. Since negative z values mean that the vertex is in front of the camera (rather than behind the camera) this convention guarantees that the surface shines with maximum strength precisely when the light vector and normal vector are coincident.

In order to find the perturbation in the normal the tangent space must be correctly calculated. Most often the normal is perturbed in a fragment shader after applying the model and view matrices. Typically the geometry provides a normal and tangent. The tangent is part of the tangent plane and can be transformed simply with the linear part of the matrix (the upper 3×3). However, the normal needs to be transformed by the inverse transpose. Most applications will want cotangent to match the transformed geometry (and associated UVs). So instead of enforcing the cotangent to be perpendicular to the tangent, it is generally preferable to transform the cotangent just like the tangent. Let t be tangent, b be cotangent, n be normal, M3×3 be the linear part of model matrix, and V3×3 be the linear part of the view matrix.

Interactive normal map rendering was originally only possible on PixelFlow, a parallel rendering machine built at the University of North Carolina at Chapel Hill.[citation needed] It was later possible to perform normal mapping on high-end SGI workstations using multi-pass rendering and framebuffer operations or on low end PC hardware with some tricks using paletted textures. However, with the advent of shaders in personal computers and game consoles, normal mapping became widely used in commercial video games starting in late 2003. 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. Many authoring pipelines use high resolution models baked into low/medium resolution in game models augmented with normal maps.

Basic normal mapping can be implemented in any hardware that supports palettized textures. The first game console to have specialized normal mapping hardware was the Sega Dreamcast. However, Microsoft’s Xbox was the first console to widely use the effect in retail games. Out of the sixth generation consoles, only the PlayStation 2’s GPU lacks built-in normal mapping support. Games for the Xbox 360 and the PlayStation 3 rely heavily on normal mapping and are beginning to implement parallax mapping. The Nintendo 3DS has been shown to support normal mapping, as demonstrated by Resident Evil Revelations and Metal Gear Solid: Snake Eater.

Dee Anthony

Dee Anthony (April 9, 1926 – October 25, 2009) was an American talent manager who started in the business with fellow Bronx native Jerry Vale. After meeting Tony Bennett in 1954 at a nightclub in Yonkers, New York, he ended up representing the singer for more than a decade. From the 1960s to the mid-1990s, Anthony managed a number of music artists, including Humble Pie, Traffic, Jethro Tull, Joe Cocker, Gary Wright, Montrose, Devo and Armageddon, with his most notable client being Peter Frampton.

He was born on April 9, 1926, and grew up in the Bronx as Anthony D’Addario, changing his name in the late 1950s. During World War II, he served in the United States Navy in the submarine service. After completing his military service wholesale softball socks, he started booking events for his friend Jerry Vale, ultimately becoming the road manager for crooner Tony Bennett. He started Bandana Enterprises with his brother in 1968, which managed artists such as Joe Cocker, Ten Years After and the J. Geils Band.

The English band Humble Pie had brought Anthony on in 1969 to help them gain entry into the American music scene, hoping to build on Anthony’s success with helping other British groups, including Spooky Tooth and Traffic, reach into the U.S. record market. Anthony had the band tour extensively around the United States, and Humble Pie produced the moderately successful live album Performance Rockin’ the Fillmore in 1971 which helped them gain recognition with American record purchasers.

Frampton remained with Anthony as his manager after he left Humble Pie to perform on his own, and Anthony had Frampton follow the same model of extensive touring that they had used previously. The resulting album in 1976, Frampton Comes Alive!, became one of the best-selling live albums in the United States history and established Frampton’s status in the American hard rock scene. His subsequent albums, such as I’m in You in 1977, never attained the heights of his original live album. Anthony put Frampton in the 1978 film Sgt. Pepper’s Lonely Hearts Club Band, which failed both commercially and critically, with Janet Maslin of The New York Times deriding the movie as “a business deal set to music”. Frampton would leave Anthony shortly thereafter.

From the 1980s until his retirement in the mid-1990s, Anthony would represent acts such as Peter Allen, Basia and Devo. He had a small role in the 1982 Jamaican film “Countryman.”

Fred Goodman recorded Anthony’s three rules of success in his 1997 book Mansion on the Hill: “1) Get the money. 2) Remember to get the money; and, 3) Don’t forget to always remember to get the money.”

The Southport, Connecticut, resident died at age 83 on October 25, 2009 at Norwalk Hospital of pneumonia refillable water bottles. He was survived by his second wife, Valerie Anthony, as well as by four daughters and six grandchildren. An earlier marriage ended in divorce. Anthony’s daughter, Michele Anthony, is the executive vice president of the Universal Music Group. She was formerly the president and chief operating officer of Sony Music runners water bottle belt.