Shadow mapping

Résumé

Shadow mapping or shadowing projection is a process by which shadows are added to 3D computer graphics. This concept was introduced by Lance Williams in 1978, in a paper entitled "Casting curved shadows on curved surfaces." Since then, it has been used both in pre-rendered and realtime scenes in many console and PC games. Shadows are created by testing whether a pixel is visible from the light source, by comparing the pixel to a z-buffer or depth image of the light source's view, stored in the form of a texture. Principle of a shadow and a shadow map If you looked out from a source of light, all the objects you can see would appear in light. Anything behind those objects, however, would be in shadow. This is the basic principle used to create a shadow map. The light's view is rendered, storing the depth of every surface it sees (the shadow map). Next, the regular scene is rendered comparing the depth of every point drawn (as if it were being seen by the light, rather than

Source officielle

https://en.wikipedia.org/wiki/Shadow_mapping

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ELECTROSTATIC CLAMPING CHUCK FOR NANOSTENCILS

Hannes Bleuler, Jürgen Brugger, Marc Antonius Friedrich van den Boogaart

There is growing interest in using alternative, resistless patterning techniques. Stencil lithography or shadow masking is one of the possible solutions. By means of physical vapor deposition many different materials can be evaporated in vacuum and patterned through a mask onto a substrate. This can be done in static and dynamic mode. The LMIS1 group is currently developing stencils with improved characteristics as well as a setup that will allow dynamic stencil deposition. In such a setup, a nanostencil is mounted onto a xy-stage and is then moved relative to the substrate. The goal of this project is to develop a miniaturized electrostatic chuck that allows the clamping of nanostencils in a reliable and user-friendly manner.

2006

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Automatic and Accurate Shadow Detection using Near-Infrared Information

Dominic Rüfenacht, Sabine Süsstrunk

We present a method to automatically detect shadows in a fast and accurate manner by taking advantage of the inherent sensitivity of digital camera sensors to the near-infrared (NIR) part of the spectrum. Dark objects, which confound many shadow detection algorithms, often have much higher reflectance in the NIR. We can thus build an accurate shadow candidate map based on image pixels that are dark both in the visible and NIR representations. We further refine the shadow map by incorporating ratios of the visible to the NIR image, based on the observation that commonly encountered light sources have very distinct spectra in the NIR band. The results are validated on a new database, which contains visible/NIR images for a large variety of real-world shadow creating illuminant conditions, as well as manually labelled shadow ground truth. Both quantitative and qualitative evaluations show that our method outperforms current state-of-the-art shadow detection algorithms in terms of accuracy and computational efficiency.

Institute of Electrical and Electronics Engineers2014

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