We attempt to recover a 2D chromaticity intrinsic variation of a single RGB image which is independent of lighting, without requiring any prior knowledge about the camera. The proposed algorithm aims to learn an invariant direction for projecting from 2D color space to the greyscale intrinsic image. We notice that along this direction, the entropy in the derived invariant image is minimized. Th...

It is proved that if C is a convex body in R" then C has an affine image C (of nonzero volume) so that if P is any 1-codimensional orthogonal projection, \PC\>\C\{tt~l)/n. It is also shown that there is a pathological body, K , all of whose orthogonal projections have volume about \fh~ times as large as |Ä"| . 0. Introduction The problems discussed in this paper concern the areas of shadows (or...

The image irradiance of a three-dimensional object is known to be the function of three components: the distribution of light sources, the shape, and reflectance of a real object surface. In the past, recovering the shape and reflectance of an object surface from the recorded image brightness has been intensively investigated. On the other hand, there has been little progress in recovering illu...

Given a set of n non-overlapping unit disks in the plane, a line ` is called blocked if it intersects at least one of the disks and a point p is called a shadow point if all lines containing p are blocked. In addition, a maximal closed set of shadow points is called a shadow region. We derive properties of shadow regions, and present an O(n) algorithm that outputs all shadow regions. We prove t...

Shadows have been one of the most serious problems for vegetation segmetation, espescially under conditions of natural random airflow and human or vehicle disturbance. A video sequence processing method has developed in this paper to identify and eliminate crop shadows. The method comprises pixel models and algorithms explained in a probable learning framework. Expectation maximization (EM) for...

In our digital art, we design a folding fan as an interactive magic device. You can use it to play with gas around the world of illusions. Although gas could not be seen in our real world, we still want to interact with it in our illusions by the element of bubble shadows. Opening and swinging the folding fan can blow the bubble shadows away; closing and swinging it can break bubbles. If the ma...

Shadows provide important visual cues, increasing the viewer’s ability to accurately interpret intra-object and inter-object spatial relationships in images of computer-generated scenes [8]. Moreover, shadows dramatically increase the ”realism” of synthetic scenes. We propose a new approach to computing shadows based on the image-space technique known as ”shadow mapping”. Our approach builds on...

In the context of mixed reality, it is difficult to simulate shadow interaction between real and virtual objects when only an approximate geometry of the real scene and the light source is known. In this paper, we present a realtime rendering solution to simulate colour-consistent virtual shadows in a real scene. The rendering consists of a three-step mechanism: shadow detection, shadow protect...

Front-projection display systems suffer from a fundamental problem: the user can easily and inadvertently block the projector, creating shadows. The framework we present in this paper enables a front-projected display system to solve this problem and remove display surface shadows in real-time. Shadows are an example of radiometric inconsistencies, which cause a number of challenges in building...

Let B be a building over a type set I . Suppose J ⊆ I meets every connected component of the diagram of B and let (P,L) be the point-line truncation of the J -Grassmann geometry of B. We present a theorem that allows one to identify shadows of apartments of residues of B in the point-collinearity graph of (P,L). Also, other results related to shadows of apartments of residues and shadows of res...