Labeling Line Drawings with Hidden-Part-Drawn of Planar Object with Trihedral Vertices

Although line drawings consist of only line segments on a plane, they convey much information about the three-dimensional object structures. For a computer interpreting line drawings, some intelligent mechanism is required to extract three-dimensional information from the two-dimensional line drawings. In this paper, a new labeling theory and method are proposed for the two-dimensional line drawing with hidden-part-draw of a three-dimensional planar object with trihedral vertices. Some rules for labeling line drawing are established. There are 24 kinds of possible junctions for line drawing with hidden-part-draw, in which there are 8 possible Y and 16 W junctions. The three problems are solved that Sugihara＇s line drawing labeling technique exists. By analyzing the projections of the holes in manifold planar object, we have put forward a labeling method for the line drawing. Our labeling theory and method can discriminate between correct and incorrect hidden-part-draw natural line drawings. The hidden-part-draw natural line drawings can be labeled correctly by our labeling theory and method, whereas the labeling theory of Sugihara can only label the hidden-part-draw unnatural line drawings in which some visible lines must be drawn as hidden lines, and some invisible lines must be drawn as continuous lines.

3D object reconstruction by point coordinates of 2D line drawings

It is a research subject in computer vision to 3D reconstruction of an object represented by a single 2D line drawing. Previous works on 3D reconstruction from 2D line drawings focus on objects with lines, plane, view, and so on. This paper mainly studies the 3D reconstruction from 2D line drawings. Besides, a new approach is proposed： it is that for the research of the point coordinates of 2D line drawings, so as to achieve the object reconstruction by the reconstruction of point coordinates. The reconstruction process includes： （1） the collection of point coordinates （X,Y） of 2D line drawings; （2） the derivation of mathematical formula about the reconstruction of the point of 2D line drawings, and calculating the corresponding point of the 3D coordinates; （3） the regeneration of 3D graphics with 3D points; （4） analyze error by the proportional of parallel of axonometric projection, in order to prove the accuracy of the method.

Drawing a Line in the Sand

An Inner Mongolian woman takes on the desert and converts extensive arid regions into arable land by Ni Yanshuo CONVERTING vast tracks of desert into arable land is no easy task, even using the most advanced technology.Yet a woman who hails from north China’s Inner Mongolia Autonomous Region met this challenge head on.Using the helping hands of other determined women,she has made remarkable progress in pushing back the sands of time.

Recovering the Shape of Planar Object Depicted by a Line Drawing under Axonometric Projection

A new approach is proposed for automatically creating B-rep models of a three-dimensional planar object from a line drawing depicting the object under orthographically axonometric projection. A new line parameterization that satisfies the uniqueness, boundedness and uniformness for representing lines in 2D and 3D space is given. According to the location relation between lines and planes of object depicted by the line drawing, some constraints about object’s 3D information are produced and a linear system based on those constraints is established. 3D information of a planar body can be obtained by solving the linear system. It is proved that, during the processing, there existed at least four degrees of freedom. It is more convenient to use information about lines and planes instead of points and planes for computer vision and intelligent CAD systems to interpret line drawings of planar objects.

Discrimination of Junctions in Line Drawing by Computer

For discrimination of the common W-junction and Y-junction in the labels of line drawing for a three-dimensional manifold plane surface with trihedral vertices, the existing algorithms are almost using angles between two adjacent lines and W-junction and Y- junction＇s definitions, and other complex methods. This passage gives four methods with their detailed mathematical inference processes in order to use these algorithms implemented by computer. The algorithms listed are Angle Summation method and Points to the Line method, Triangle methods which are the Triangle Area method and the Cross method. When the computer programs discriminate junctions, by comparison, the Angle Summation method and Points to the Line method are less efficacious than the Triangle method, and Cross method is more efficacious than the Triangle Area method in the Triangle method.

3D reconstruction of complex curved objects from line drawings

An active research topic in computer vision and graphics is developing algorithms that can reconstruct the 3D surface of curved objects from line drawings. There are a number of algorithms have been dedicated to solve this problem, but they can＇t solve this problem when the geometric structure of a curved object becomes complex. This paper proposes a novel approach to reconstructing a complex curved 3D object from single 2D line drawings. Our approach has three steps： （1） decomposing a complex line drawing into several simpler line drawings and transforming them into polyhedron; （2） reconstructing the 3D wireframe of curved object from these simpler line drawings and generating the curved faces; （3） combining the 3D objects into the complete objects. A number of examples are given to demonstrate the ability of our approach to successfully perform reconstruction of curved objects which are more complex than previous methods.

3D Reconstruction from 2D Line Drawings only with Visible Vertices and Edges

The human vision system can reconstruct a 3D object easily from single 2D line drawings even if the hidden lines of the object are invisible. Now, there are many methods have emulated this ability, but when the hidden lines of the object are invisible, these methods cannot reconstruct a complete 3D object. Therefore, we put forward a new algorithm to settle this hard problem. Our approach consists of two steps： （1） infer the invisible vertices and edges to complete the line drawing, （2） propose a vertex-based optimization method to reconstruct a 3D object.

Research on Distance Judgement Method from Point to Line to Generate a Line

Regarding the problem that the traditional straight-line generating has a low accuracy, we study straightline generating with the distance of point to line. We explore generating a line to approximate the ideal line and the issue is to pick out the pixel point of approximating the ideal line. The paper plays a significant scientific role in elucidating linear optimization norm and it lays a foundation for showing a straight line. The algorithm is valuable for computer graphics.

Cognitive mechanism related to line drawings and its applications in intelligent process of visual media： a survey

Line drawings, as a concise form, can be recognized by infants and even chimpanzees. Recently, how the visual system processes line-drawings attracts more and more attention from psychology, cognitive science and computer science. The neuroscientific studies revealed that line drawings generate similar neural actions as color photographs, which give insights on how to efficiently process big media data. In this paper, we present a comprehensive survey on line drawing studies, including cognitive mechanism of visual perception, computational models in computer vision and intelligent process in diverse media applications. Major debates, challenges and solutions that have been addressed over the years are discussed. Finally some of the ensuing challenges in line drawing studies are outlined.

Expressive line drawings of human faces from range images

We propose a novel technique to extract features from a range image and use them to produce a 3D pen-and-ink style portrait similar to a traditional artistic drawing. Unlike most previous template-based, component-based or example-based face sketching methods, which work from a frontal photograph as input, our system uses a range image as input. Our method runs in real-time for models of moderate complexity, allowing the pose and drawing style to be modified interactively. Portrait drawing in our system makes use of occluding contours and suggestive contours as the most important shape cues. However, current 3D feature line detection methods require a smooth mesh and cannot be reliably applied directly to noisy range images. We thus present an improved silhouette line detection algorithm. Feature edges related to the significant parts of a face are extracted from the range image, connected, and smoothed, allowing us to construct chains of line paths which can then be rendered as desired. We also incorporate various portrait-drawing principles to provide several simple yet effective non- photorealistic portrait renderers such as a pen-and-ink shader, a hatch shader and a sketch shader. These are able to generate various life-like impressions in different styles from a user-chosen viewpoint. To obtain satisfactory results, we refine rendered output by smoothing changes in line thickness and opacity. We are careful to provide appropriate visual cues to enhance the viewer＇s comprehension of the human face. Our experimental results demonstrate the robustness and effectiveness of our approach, and further suggest that our approach can be extended to other 3D geometric objects.

Line drawing via saliency map and ETF

Line drawing is a means of superior visual communication which can effectively convey useful information to viewers.Artists usually draw what they see rather than what exists,which means the most attractive object is emphasized while the rest are inhibited.Moreover,artists draw the whole object with coherent lines instead of fractured lines,which also contribute to the outstanding visual effect.From these perspectives,generating line drawings with saliency and coherence remains a great challenge.Existing line drawing generation methods ignore these important properties and cannot generate coherent lines in some cases since they do not take into account how artists draw a picture.To this end,a novel saliency-aware line drawing method was proposed to better grasp the viewer’s attention on an image.First,a saliency enhanced line extraction method combining saliency map and edge tangent flow was proposed to ensure the saliency and coherence of lines,especially in salient but low contrast areas.Then,the salient information was highlighted while irrelevant details were eliminated by inhibiting lines in less salient areas to enhance the saliency of the line drawing.Finally,the transparency of lines was adjusted to further emphasize important information.Various results showed that our method can generate line drawings with better visual saliency and coherence than the state-of-the-art methods.

Surveys on line drawing simplification for Chinese cultural computing

In the recent decade,many approaches of rough line drawing simplification were proposed,but they are not well summarized yet,especially from the perspective of Chinese cultural computing.In this paper,a comprehensive review of existing line drawing simplification methods was presented,including their algorithms,advantages/disadvantages,inputs/outputs,datasets and source codes,etc.For raster line drawings,related simplification work was discussed according to four main categories:fitting-based methods,tracing-based methods,field-based methods,and learning-based methods.For vector line drawings,a deep investigation was introduced for two major steps of simplification:stroke grouping and stroke merging.Finally,conclusions were given,key challenges and future directions of line drawing simplification for Chinese traditional art were thoroughly discussed.

Exploring Local Regularities for 3D Object Recognition

In order to find better simplicity measurements for 3D object recognition, a new set of local regularities is developed and tested in a stepwise 3D reconstruction method, including localized minimizing standard deviation of angles（L-MSDA）, localized minimizing standard deviation of segment magnitudes（L-MSDSM）, localized minimum standard deviation of areas of child faces （L-MSDAF）, localized minimum sum of segment magnitudes of common edges （L-MSSM）, and localized minimum sum of areas of child face （L-MSAF）. Based on their effectiveness measurements in terms of form and size distortions, it is found that when two local regularities： L-MSDA and L-MSDSM are combined together, they can produce better performance. In addition, the best weightings for them to work together are identified as 10% for L-MSDSM and 90% for L-MSDA. The test results show that the combined usage of L-MSDA and L-MSDSM with identified weightings has a potential to be applied in other optimization based 3D recognition methods to improve their efficacy and robustness.

Psychological potential field and human eye fixation on binary line-drawing images: A comparative experimental study

Quantitatively evaluating the psychological and perceptual effects of objects is an important issue,but is difficult. In cognitive studies, the psychological potential field(PPF), which represents psychological intensities in vision and can be calculated by applying computational algorithms to digital images, may help with this issue. Although studies have reported using the PPF to evaluate psychological effects, such as impressions, detailed investigations on how the PPF represents psychological perception and its limitations have not yet been performed. Another relevant tool is the fixation map, which visualizes human eye fixations;this map is generated from actual measurements acquired by eye-tracking and does not represent psychological effects directly. Although the PPF and the fixation map are based on visual imaging, they have never been compared. In this paper, we do so for the first time, using psychological and perceptual properties of line-drawing images. The results demonstrate the difference between these methods, including their representation of different properties with respect to visual perception. Moreover, the similarity between the two methods highlights the possibility of assessing perceptual phenomena such as categorization and cognition of objects based on human vision.

Stylized strokes for coherent line drawings

Temporal coherence is one of the central challenges for rendering a stylized line. It is especially difficult for stylized contours of coarse meshes or nonuniformly sampled models, because those contours are polygonal feature edges on the models with no continuous correspondences between frames. We describe a novel and simple technique for constructing a 2D brush path along a 3D contour. We also introduce a 3D parameter propagation and re-parameterization procedure to construct stroke paths along the 2D brush path to draw coherently stylized feature lines with a wide range of styles. Our method runs in real-time for coarse or non-uniformly sampled models, making it suitable for interactive applications needing temporal coherence.

A Line Extraction Algorithm for Hand Drawings

This paper presents an algorithm for extracting lines from hand drawings.It starts from contour pixel tracing, fits them into contour segments, and thenextracts skeleton lines from the contour segments. The algorithm finds all con-tours in one scan of the input matrix without detecting and marking multiplepixels. In line extraction, the method Elastic Contour Segment nacing is pro-posed which extracts lines by referring to the contour segments at both sides,overcoming noise and passing through blotted areas by fitting and extrapolation.Experiments on free hand mechanical drawings, sketches, letter/numerals,as well as Chinese characters are carried out and satisfactory results are achieved.

Portrait drawing from corresponding range and intensity images

We propose a real-time rendering system for automatically creating a caricature drawing, i.e., an exaggerated portrait, of a human face, based on simultaneous use of a range image (or 3D mesh) and a registered photograph of the same face. Combining these information sources provides complementary information. Significant geometric lines such as occluding contours and suggestive contours are extracted from the range data, while textured areas corresponding to shading features are extracted from the photograph. These are combined, and then distorted to produce the final caricature. The final output may be produced using a choice of non-photorealistic rendering styles. Our system method works well for low resolution range images; for these it is fast enough to allow the viewpoint to be chosen in real time. The final output combines significant lines, textured areas, and optional shading, giving a pleasing result which preserves not only the shape cues of the geometric description, but also other essential visual characteristics of the facial image that cannot be deduced from geometry alone.

Where Do We Draw the Line With Online Manhunts?

In early July, a manhunt message posted on dahe.cn, a local Web portal in central China’s Henan Province, caused great concern among netizens. In the post, Zhao Guanle, a police officer in Ruyang County who was investigating several ATM fraud cases, provided a screenshot of the face of a young man who was suspected of committing the fraud and asked netizens knowing the man to help the police

Where Do You Draw the Line In Copyright Infringement?

Famous Chinese film director Chen Kaige has made a big comeback with the release of his visually breathtaking movie The Promise, a $44 million mythological epic said to be the most expensive film in the history of Chinese cinema. As with every project Chen is involved in, the film has drawn extensive attention before and after its screening. Having been given a Golden Globe nomination for