翻訳と辞書 Words near each other ・ Ambient Devices ・ Ambient Dub Volume I ・ Ambient Entertainment ・ Ambient house ・ Ambient industrial ・ Ambient intelligence ・ Ambient ionization ・ Ambient isotopy ・ Ambient lighting ・ Ambient media ・ Ambient Monkeys ・ Ambient music ・ Ambient music design ・ Ambient network ・ Ambient noise level ・ Ambient occlusion ・ Ambient optic array ・ Ambient power ・ Ambient pressure ・ Ambient space ・ Ambient Weather ・ AmbientTalk ・ Ambierle ・ AmbieSense ・ Ambiga Sreenevasan ・ Ambigai Neril Vanthaal ・ Ambigol ・ Ambigolimax ・ Ambigolimax valentianus ・ Ambigram Dictionary Lists mini英和辞書 mini和英辞書 Webster 1913 Latin-English FOLDOC Wikipedia English ウィキペディア

翻訳と辞書　辞書検索 [ 開発暫定版 ] スポンサード リンク Ambient occlusion ： ウィキペディア英語版 Ambient occlusion In computer graphics, ambient occlusion is a shading and rendering technique used to calculate how exposed each point in a scene is to ambient lighting. The interior of a tube is typically more occluded (and hence darker) than the exposed outer surfaces, and the deeper you go inside the tube, the more occluded (and darker) the lighting becomes. Ambient occlusion can be seen as an accessibility value that is calculated for each surface point. In scenes with open sky this is done by estimating the amount of visible sky for each point, while in indoor environments only objects within a certain radius are taken into account and the walls are assumed to be the origin of the ambient light. The result is a diffuse, non-directional shading effect that casts no clear shadows but that darkens enclosed and sheltered areas and can affect the rendered image's overall tone. It is often used as a post-processing effect. Unlike local methods such as Phong shading, ambient occlusion is a global method, meaning that the illumination at each point is a function of other geometry in the scene. However, it is a very crude approximation to full global illumination. The appearance achieved by ambient occlusion alone is similar to the way an object might appear on an overcast day. ==Implementation== In real-time applications, such as computer games, Screen space ambient occlusion can be used as a faster approximation of true ambient occlusion, using pixel depth rather than scene geometry to form an ambient occlusion map. However, newer technologies are making true ambient occlusion feasible even in real-time. Ambient occlusion is related to accessibility shading, which determines appearance based on how easy it is for a surface to be touched by various elements (e.g., dirt, light, etc.). It has been popularized in production animation due to its relative simplicity and efficiency. In the industry, ambient occlusion is often referred to as "sky light". The ambient occlusion shading model has the nice property of offering a better perception of the 3D shape of the displayed objects. This was shown in a paper where the authors report the results of perceptual experiments showing that depth discrimination under diffuse uniform sky lighting is superior to that predicted by a direct lighting model. The occlusion $A\_\backslash bar\; p$ at a point $\backslash bar\; p$ on a surface with normal $\backslash hat\; n$ can be computed by integrating the visibility function over the hemisphere $\backslash Omega$ with respect to projected solid angle: $$ A_\bar p = \frac \int_ V_ (\hat n \cdot \hat\omega ) \, \operatorname\omega where $V\_$ is the visibility function at $\backslash bar\; p$, defined to be zero if $\backslash bar\; p$ is occluded in the direction $\backslash hat\backslash omega$ and one otherwise, and $\backslash operatorname\backslash omega$ is the infinitesimal solid angle step of the integration variable $\backslash hat\backslash omega$. A variety of techniques are used to approximate this integral in practice: perhaps the most straightforward way is to use the Monte Carlo method by casting rays from the point $\backslash bar\; p$ and testing for intersection with other scene geometry (i.e., ray casting). Another approach (more suited to hardware acceleration) is to render the view from $\backslash bar\; p$ by rasterizing black geometry against a white background and taking the (cosine-weighted) average of rasterized fragments. This approach is an example of a "gathering" or "inside-out" approach, whereas other algorithms (such as depth-map ambient occlusion) employ "scattering" or "outside-in" techniques. In addition to the ambient occlusion value, a "bent normal" vector $\backslash hat\_b$ is often generated, which points in the average direction of unoccluded samples. The bent normal can be used to look up incident radiance from an environment map to approximate image-based lighting. However, there are some situations in which the direction of the bent normal is a misrepresentation of the dominant direction of illumination, e.g., In this example, light may reach the point p only from the left or right sides, but the bent normal points to the average of those two sources, which is, unfortunately, directly toward the obstruction. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Ambient occlusion」の詳細全文を読む スポンサード リンク 翻訳と辞書 : 翻訳のためのインターネットリソース Copyright(C) kotoba.ne.jp 1997-2016. All Rights Reserved.