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{{More footnotes|date=February 2010}}
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[[Image:Normal map example.png|thumb|350px|Normal mapping used to re-detail simplified meshes.]]
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 [[polygonal modeling|polygon]]s. A common use of this technique is to greatly enhance the appearance and details of a [[low poly|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 corresponds to the X, Y, and Z coordinates, respectively, of the [[surface normal]].
 
== History ==
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,<ref>Krishnamurthy and Levoy, ''[http://www-graphics.stanford.edu/papers/surfacefitting/ Fitting Smooth Surfaces to Dense Polygon Meshes]'', SIGGRAPH 1996</ref> where this approach was used for creating [[displacement mapping|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,<ref>Cohen et al., [http://www.cs.unc.edu/~geom/APS/APS.pdf Appearance-Preserving Simplification], SIGGRAPH 1998 '''(PDF)'''</ref> and  "A general method for preserving attribute values on simplified meshes" by Cignoni et al. IEEE Visualization '98.<ref>Cignoni et al., [http://vcg.isti.cnr.it/publications/papers/rocchini.pdf A general method for preserving attribute values on simplified meshes], IEEE Visualization 1998 '''(PDF)'''</ref>
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 mapping|texture coordinates]], [[displacement mapping|displacements]], etc.) in a way that is not dependent on how the low-detail model was created. The combination of storing normals in a texture, with the more general creation process is still used by most currently available tools.
 
==How it works==
[[File:Normal map example with scene and result.png|thumb|upright=1.8|Example of a normal map (center) with the scene it was calculated from (left) and the result when applied to a flat surface (right).]]
To calculate the [[Lambertian]] (diffuse) lighting of a surface, the unit [[Vector (geometric)|vector]] from the shading point to the light source is [[dot product|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.
 
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, 0} 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 (<math>0.3^2+0.4^2+(-0.866)^2=1</math>). Coordinate ''z'' (blue) minus sign flipped, because need match normal map normal vector with eye (viewpoint or camera) vector or light vector (because sign "-" for ''z'' axis means vertex is in front of camera and not behind camera; when light vector and normal vector match surface shined with maximum strength).
 
==Calculating tangent space==
{{Expand section|more math|date=October 2011}}
In order to find the perturbation in the normal the tangent space must be correctly calculated.<ref>Mikkelsen, [http://image.diku.dk/projects/media/morten.mikkelsen.08.pdf Simulation of Wrinkled Surfaces Revisited], 2008 '''(PDF)'''</ref>
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 [[Affine transformation|linear]] part of the matrix
(the upper 3x3). However, the normal needs to be transformed by the [[Surface_normal#Transforming_normals|inverse transpose]]. Most applications will want cotangent to
match the transformed geometry (and associated uv's). 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, ''M<sub>3x3</sub>'' be the linear part of model matrix, and ''V<sub>3x3</sub>'' be the linear part of the view matrix.
:<math>t' = t \times M_{3x3} \times V_{3x3}</math>
:<math>b' = b \times M_{3x3} \times V_{3x3}</math>
:<math>n' = n \times (M_{3x3} \times V_{3x3})^{-1T} = n \times M_{3x3}^{-1T} \times V_{3x3}^{-1T}</math>
 
==Normal mapping in video games==
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|date=February 2012}} It was later possible to perform normal mapping on high-end [[Silicon Graphics|SGI]] workstations using multi-pass rendering and [[framebuffer]] operations<ref>Heidrich and Seidel, [http://www.cs.ubc.ca/~heidrich/Papers/Siggraph.99.pdf Realistic, Hardware-accelerated Shading and Lighting], SIGGRAPH 1999 '''(PDF)'''</ref> or on low end PC hardware with some tricks using paletted textures.  However, with the advent of [[shader]]s 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.
 
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 (console)|Xbox]] was the first console to widely use the effect in retail games. Out of the [[History of video game consoles (sixth generation)|sixth generation consoles]], only the [[PlayStation 2]]'s [[PlayStation 2#Technical specifications|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#Metal Gear Solid 3: Snake Eater 3D|Metal Gear Solid: Snake Eater]]''.
 
==See also==
* [[Texture mapping]]
* [[Bump mapping]]
* [[Parallax mapping]]
* [[Displacement mapping]]
* [[Reflection (physics)]]
* [[Ambient occlusion]]
* [[Depth map]]
 
==References==
{{reflist}}
 
==External links==
{{commons category}}
<!-- This links seems to be dead:  * [http://liman3d.com/tutorial_normalmaps.html Understanding Normal Maps] -->
* [http://www.game-artist.net/forums/vbarticles.php?do=article&articleid=16 Introduction to Normal Mapping]
* [http://wiki.blender.org/index.php/Manual/Bump_and_Normal_Maps Blender Normal Mapping]
* [http://vcg.isti.cnr.it/activities/geometryegraphics/bumpmapping.html Normal Mapping with paletted textures] using old OpenGL extensions.
* [http://zarria.net/nrmphoto/nrmphoto.html Normal Map Photography] Creating normal maps manually by layering digital photographs
* [http://www.3dkingdoms.com/tutorial.htm Normal Mapping Explained]
* [http://sourceforge.net/projects/simplenormalmapper Simple Normal Mapper] Open Source normal map generator
 
[[Category:Demo effects]]
[[Category:Texture mapping]]
[[Category:Virtual reality]]

Latest revision as of 15:19, 16 September 2014

Most people desire to know the answer to the question: How many calories do I have to eat every day to get rid of fat? This query is usually followed by: Are all calories built equal?

I understand what you're thinking....."There's no technique bmr calculator I may drink that much water!" But rest assured, you can, plus the body usually thank you for it. At initial, you will invest a lot of time inside the bathroom. But in regarding two weeks, the body is totally hydrated plus a bathroom breaks might level off. During those first limited weeks of frequent pit stops, just think of it as piece of the exercise system. Consider all of the squats you're doing, and if you wear clothing like overalls, you'll be getting some good stretching inside as you pull them on and off!

We may be male or female, nevertheless we nonetheless want muscle to raise a basal metabolic rate. This is a measure of how numerous calories the body burns each day. Already we understand which too countless unused calories are bad for your health, thus we want to start to pay attention to how much muscle is on a body. It is worthwhile.

How much water is enough? Probably not the eight glasses we've constantly been told. Eight 8-ounce glasses is fine in the event you only weigh 130 pounds. To calculate how much water you require, divide a fat inside half. You could drink that many ounces of water each day. If you weigh 180 pounds, you should drink 90 ounces of water.

Consume no less than 1000 calories regularly. The optimal caloric consumption must be lower than 500 calories compared to what exactly is essential according to a bmr. There are many tools accessible online that aid we calculate a BMR.

9) Keep a log - Keeping a food diary helps we pin point the eating pattern plus will help you to conveniently modify it. If possible, have your Registered Dietitian review your diary.

I hope you're inside the usual range, nevertheless should you are overweight we can plan several fat reduction program considering the BMR and present activity level and hopefully improve a wellness.