Line Drawing Algorithms Research Articles

GPU加速的表意式体模型线绘制算法

Existing line drawing algorithms for volumes extract feature lines by tracing randomly selected seeds, which is known to have severe temporal coherence problems. We propose a GPU-based line drawing algorithm framework for volume data. The algorithm extracts all feature lines in every frame, eliminating the discontinuity artifacts in successive frames. Firstly, we propose a parallel algorithm to extract feature line segments in each cell in the geometry shader. To determine the visibility of feature lines, we use splatting to render a depth map for each frame, achieving much higher performance than the ray-casting method adopted in previous approaches. Correct visibility is obtained by using adaptive depth offsets. To store the large volume data in the high-speed video memory, we propose efficient data pruning and encoding schemes, which remarkably reduce the memory consumption and bandwidth, while maintaining the line drawing quality. Experimental results show that, our method can render high quality line drawings with temporal coherence, with a rendering speed that is an order of magnitude faster than previous CPU-based methods using seed-and-traversal.

MIMIC: An Innovative Methodology for Determining Mobile Laser Scanning System Point Density

Understanding how various Mobile Mapping System (MMS) laser hardware configurations and operating parameters exercise different influence on point density is important for assessing system performance, which in turn facilitates system design and MMS benchmarking. Point density also influences data processing, as objects that can be recognised using automated algorithms generally require a minimum point density. Although obtaining the necessary point density impacts on hardware costs, survey time and data storage requirements, a method for accurately and rapidly assessing MMS performance is lacking for generic MMSs. We have developed a method for quantifying point clouds collected by an MMS with respect to known objects at specified distances using 3D surface normals, 2D geometric formulae and line drawing algorithms. These algorithms were combined in a system called the Mobile Mapping Point Density Calculator (MIMIC) and were validated using point clouds captured by both a single scanner and a dual scanner MMS. Results from MIMIC were promising: when considering the number of scan profiles striking the target, the average error equated to less than 1 point per scan profile. These tests highlight that MIMIC is capable of accurately calculating point density for both single and dual scanner MMSs.

The relative effectiveness of different line drawing algorithms at conveying 3D shape

The relative effectiveness of different line drawing algorithms at conveying 3D shape

Where do people draw lines?

This paper presents the results of a study in which artists made line drawings intended to convey specific 3D shapes. The study was designed so that drawings could be registered with rendered images of 3D models, supporting an analysis of how well the locations of the artists' lines correlate with other artists', with current computer graphics (CG) line definitions, and with the underlying differential properties of the 3D surface. Lines drawn by artists in this study largely overlapped one another, particularly along the occluding contours of the object. Most lines that do not overlap contours overlap large gradients of the image intensity and correlate strongly with predictions made by recent line-drawing algorithms in CG. A few were not well described by any of the local properties considered in this study. The result of our work is a publicly available data set of aligned drawings, an analysis of where lines appear in that data set based on local properties of 3D models, and algorithms to predict where artists will draw lines for new scenes.

미술가들의 음영 표현 특성과 CG 쉐이딩 알고리즘 간의 상관관계 분석

최근 컴퓨터 그래픽스와 사용자의 인지를 결합한 다양한 연구들이 진행되고 있다. Cole 등은 미술가들의 라인 드로잉 데이터를 수집하여 기존의 CG(Computer-Generated) 라인 드로잉 알고리즘들이 미술가들의 드로잉 특성을 반영하고 있는지 비교하고, 사용자들이 어떤 라인 드로잉 알고리즘의 결과에서 형태를 효과적으로 인지하는지 평가하는 실험을 수행하였다. 그러나 라인 드로잉 알고리즘의 결과보다 BRDF 쉐이딩 모델이 적용된 결과에서 형태를 더욱 효과적으로 인지한다는 결과를 보였는데, 이는 음영이 형태 정보를 전단하기에 더욱 효과적인 요소임을 반증한다. 따라서 본 논문에서는 물체에서 인지한 음영과 미술가들의 음영 표현, 그리고 CG 쉐이딩 알고리즘 간의 상관관계에 대해서 연구한다. 특히, 미술가들의 음영 표현 특성과 CG 쉐이딩 알고리즘에서 나타나는 특성에 초점을 맞추고 이를 정량적으로 분석한다. 본 논문에서 수집한 실험 데이터 및 분석 결과는 효과적인 형태 전달을 목적으로 하는 새로운 CG 쉐이딩 알고리즘을 설계하는데 활용한 것으로 기대된다. Recently, several researchers have attempted to combine human visual perception and computer graphics. Cole et. al. suggest the study results in which line drawing algorithm in computer graphics characterize the properties of line drawing made by artists. The paper also evaluates CG line drawing algorithms depending on whether people recognize effectively specific 3D shape from the image made by those CG line drawing algorithms. However, human recognizes the shape of objects more effectively in image made by BRDF shading model than line drawing algorithm. It means that the shading factor is important to recognize shape with human perception. In this paper, we analyze the correlation between shading made by human artists and that made by CG shading algorithms. The study is to characterize the mathematical properties of artists' shading and CG shading. This type of analysis can guide the future development of new CG shading algorithm in computer graphics for the purpose of shape perception.

Real-time saliency-aware video abstraction

Existing real-time automatic video abstraction systems rely on local contrast only for identifying perceptually important information and abstract imagery by reducing contrast in low-contrast regions while artificially increasing contrast in higher contrast regions. These methods, however, may fail to accentuate an object against its background for the images with objects of low contrast over background of high contrast. To solve this problem, we propose a progressive abstraction method based on a region-of-interest function derived from an elaborate perception model. Visual contents in perceptually salient regions are emphasized, whereas the background is abstracted appropriately. In addition, the edge-preserving smoothing and line drawing algorithms in this paper are guided by a vector field which describes the flow of salient features of the input image. The whole pipeline can be executed automatically in real time on the GPU, without requiring any user intervention. Several experimental examples are shown to demonstrate the effectiveness of our approach.

Data-driven curvature for real-time line drawing of dynamic scenes

This article presents a method for real-time line drawing of deforming objects. Object-space line drawing algorithms for many types of curves, including suggestive contours, highlights, ridges, and valleys, rely on surface curvature and curvature derivatives. Unfortunately, these curvatures and their derivatives cannot be computed in real-time for animated, deforming objects. In a preprocessing step, our method learns the mapping from a low-dimensional set of animation parameters (e.g., joint angles) to surface curvatures for a deforming 3D mesh. The learned model can then accurately and efficiently predict curvatures and their derivatives, enabling real-time object-space rendering of suggestive contours and other such curves. This represents an order-of-magnitude speedup over the fastest existing algorithm capable of estimating curvatures and their derivatives accurately enough for many different types of line drawings. The learned model can generalize to novel animation sequences and is also very compact, typically requiring a few megabytes of storage at runtime. We demonstrate our method for various types of animated objects, including skeleton-based characters, cloth simulation, and blend-shape facial animation, using a variety of nonphotorealistic rendering styles. An important component of our system is the use of dimensionality reduction for differential mesh data. We show that Independent Component Analysis (ICA) yields localized basis functions, and gives superior generalization performance to that of Principal Component Analysis (PCA).

Where do people draw lines?

This paper presents the results of a study in which artists made line drawings intended to convey specific 3D shapes. The study was designed so that drawings could be registered with rendered images of 3D models, supporting an analysis of how well the locations of the artists' lines correlate with other artists', with current computer graphics line definitions, and with the underlying differential properties of the 3D surface. Lines drawn by artists in this study largely overlapped one another (75% are within 1mm of another line), particularly along the occluding contours of the object. Most lines that do not overlap contours overlap large gradients of the image intensity, and correlate strongly with predictions made by recent line drawing algorithms in computer graphics. 14% were not well described by any of the local properties considered in this study. The result of our work is a publicly available data set of aligned drawings, an analysis of where lines appear in that data set based on local properties of 3D models, and algorithms to predict where artists will draw lines for new scenes.

Drawing lines by uniform packing

In this paper, we introduce a new approach to line drawing that attempts to maintain a uniform packing density of horizontal segments to diagonal segments throughout the line. While the conventional line drawing algorithms perform linear time computations to find the location of the pixels, our algorithm takes logarithmic time. Also, experimental results show that the quality of line is acceptable and comparable to the well-known Bresenham's line-drawing algorithm.

From pixels to scene graphs in introductory computer graphics courses

The field of computer graphics is expanding and evolving rapidly. Past computer graphics courses addressed low-level topics such as line drawing algorithms (Computers and Graphics 2000;24(1):151–155) while the graphics industry has moved toward scene graph representations of three-dimensional scenes. This discrepancy has moved some educators to suggest graphics courses exclude 2D topics for concentration on 3D. This paper suggests that such a switch is unnecessary and provides a course outline blending old and new topics to provide breadth and relevancy without abandoning the basics.

BRDC: binary representation of displacement code for line

In raster graphics, a line is displayed as a sequence of connected pixels that best approximate the line with minimum deviation. The displacement code of a line is a sequence of binary codes, each of which represents the displacement of a pixel on the line to its immediate predecessor pixel on the line. In fact, the displacement code records the entire process of drawing a line with successive pixels and it is deterministic for each specific line. In this paper, we study the important properties of the binary representation of displacement code, called BRDC, including calculation formula, periodicity, complement, decomposition etc. At last, we put forward an efficient adaptive multi-pixel line drawing algorithm based on exploited properties of BRDC, which demonstrates that BRDC is significant for designing efficient line drawing algorithms.

Running the line: Line drawing using runs and runs of runs

The efficiency of line drawing algorithms underwrites the performance of many rendering and visualisation systems. Therefore to significantly improve the process of line drawing, techniques have been developed to draw the line not pixel by pixel but by using higher order primitives such as runs and run length slices. In this paper we present a line drawing algorithm based on runs of runs, which is the next step in this progression. We will also discuss a number of special cases in the structure of runs and runs of runs within the line that can be used to short circuit the drawing process. These special cases can be used to help counter a common criticism that run-based techniques are less applicable for very short lines. In fact we will argue that the use of higher order primitives provides additional structural information that can be used to accelerate secondary processes within the graphics system, such as within the raster memory management.

A new antialiased line drawing algorithm

Consider a line f (x)=mx+b , 0⩽ m ⩽1 . Conventional line drawing algorithms sample (x, f (x)) on the line, where x must be an integer, and then map (x, f (x)) to the frame buffer according to the defined filter and f (x) . In this paper, we propose to simulate a sampled point (x, f (x)) by the four pixels around it where x and f (x) are not necessary to be integers. Based on the proposed low-pass filtering, we show that the effect of sampling at infinite number of points along a line segment can be achieved since the closed form of the intensities assigned to pixels exists. Furthermore, we show the coherence properties that can reduce the cost for computing these intensities.

An integral linear interpolation approach to the design of incremental line algorithms

A unified treatment of incremental line-drawing algorithms understood from the viewpoint of rounded interpolation, covering Bresenham's algorithm, run-length algorithms, and multistep versions of both.

Pixel-processing fundamentals

The key to developing line drawing algorithms is an explicit reference model for quantifying a good raster approximation. The article looks at old practices, then demonstrates the development of line and edge drawing algorithms. Computer driven raster displays introduce a higher performance, more demanding technology that benefits from systematic rules. To examine the development of a compact, integer arithmetic algorithm for line rastering, the article looks at some pixel space basics, then considers alternative measures by which closeness to a true line's locus could be evaluated. The key to effective use of all algorithms is a clear understanding of your objective function and the implications that can arise from incomplete or unintentionally fuzzy assumptions.

Improved recursive bisection line drawing algorithms

In this paper, we present modifications which reduce the logarithmic space requirements of an existing fractal line drawing algorithm to a constant while increasing its speed. The resulting algorithm is faster than many existing line drawing algorithms, especially when the lines being drawn are at or near horizontal, diagonal and vertical. Furthermore, a detailed error analysis of these algorithms is given.

Fast Scan Conversion Algorithms for Displaying Ultrasound Sector Images

Two fast algorithms for interpolation of ultrasonic sector-scans were developed. Both algorithms are based on line-drawing algorithms and are free from multiplications in the innermost loops. The algorithms were compared to the following conventional interpolators: 2-D windowed sinc, bicubic spline, 4 x 4 point bicubic spline, bilinear, and nearest neighbor. The most accurate of the two new algorithms is about eight times faster than nearest neighbor interpolation. The quantitative errors are of the same order as the errors of the nearest neighbor interpolator. The subjective image quality is between nearest neighbor and bilinear interpolation.

Fast Scan Conversion Algorithms for Displaying Ultrasound Sector Images

Two fast algorithms for interpolation of ultrasonic sector-scans were developed. Both algorithms are based on line-drawing algorithms and are free from multiplications in the innermost loops. The algorithms were compared to the following conventional interpolators: 2-D windowed sinc, bicubic spline, 4 × 4 point bicubic spline, bilinear, and nearest neighbor. The most accurate of the two new algorithms is about eight times faster than nearest neighbor interpolation. The quantitative errors are of the same order as the errors of the nearest neighbor interpolator. The subjective image quality is between nearest neighbor and bilinear interpolation.

A Run-Length Slice Line Drawing Algorithm without Division Operations

Of the two major approaches to line drawing, run-length slice algorithms are seldom used because of the division operation deemed necessary in these algorithms. The biggest advantage of these algorithms, the reduction of additions used, is considered outweighed by the division used. In this paper, a new run-length slice algorithm that does not require a division operation is presented. Furthermore, it uses the double-stepping paradigm in incremental line drawing algorithms to reduce the number of additions used by at least half. For sufficiently long lines, this algorithm uses at least 50% fewer arithmetic operations than Wu et al.'s bi-directional double-step incremental algorithm. But because of its high initialization cost, for short lines, it is less efficient. For a line with endpoints (0,0) and (δx, δy), the strategy is then to use the bi-directional Bresenham algorithm for very short lines (δx 110).

Line-drawing algorithms for parallel machines

The fact that conventional line-drawing algorithms, when applied directly on parallel machines, can lead to very inefficient codes is addressed. It is suggested that instead of modifying an existing algorithm for a parallel machine, a more efficient implementation can be produced by going back to the invariants in the definition. Popular line-drawing algorithms are compared with two alternatives; distance to a line (a point is on the line if sufficiently close to it) and intersection with a line (a point on the line if an intersection point). For massively parallel single-instruction-multiple-data (SIMD) machines (with thousands of processors and up), the alternatives provide viable line-drawing algorithms. Because of the pixel-per-processor mapping, their performance is independent of the line length orientation. >