Camera Parameters (camera + parameter)

Distribution by Scientific Domains
Engineering50%

Selected Abstracts

Automatic Light Source Placement for Maximum Visual Information Recovery

COMPUTER GRAPHICS FORUM, Issue 2 2007
P.-P. Vázquez
Abstract The automatic selection of good viewing parameters is a very complex problem. In most cases, the notion of good strongly depends on the concrete application. Moreover, when an intuitive definition of good view is available, it is often difficult to establish a measure that brings it to the practice. Commonly, two kinds of viewing parameters must be set: camera parameters (position and orientation) and lighting parameters (number of light sources, its position and eventually the orientation of the spot). The first parameters will determine how much of the geometry can be captured and the latter will influence on how much of it is revealed (i.e., illuminated) to the user. Unfortunately, ensuring that certain parts of a scene are lit does not make sure that the details will be communicated to the user, as the amount of illumination might be too small or too high. In this paper we define a metric to calculate the amount of information relative to an object that is effectively communicated to the user given a fixed camera position. This measure is based on an information-based concept, the Shannon entropy, and will be applied to the problem of automatic selection of light positions in order to adequately illuminate an object. In order to validate the results, we have carried out an experiment on users, this experiment helped us to explore other related measures. [source]

GPU-Based Nonlinear Ray Tracing

COMPUTER GRAPHICS FORUM, Issue 3 2004
Daniel Weiskopf
In this paper, we present a mapping of nonlinear ray tracing to the GPU which avoids any data transfer back to main memory. The rendering process consists of the following parts: ray setup according to the camera parameters, ray integration, ray-object intersection, and local illumination. Bent rays are approximated by polygonal lines that are represented by textures. Ray integration is based on an iterative numerical solution of ordinary differential equations whose initial values are determined during ray setup. To improve the rendering performance, we propose acceleration techniques such as early ray termination and adaptive ray integration. Finally, we discuss a variety of applications that range from the visualization of dynamical systems to the general relativistic visualization in astrophysics and the rendering of the continuous refraction in media with varying density. Categories and Subject Descriptors (according to ACM CCS): I.3.3 [Computer Graphics]: Picture/Image Generation I.3.7 [Computer Graphics]: Three-Dimensional Graphics and Realism [source]

Horizontal Roadway Curvature Computation Algorithm Using Vision Technology

COMPUTER-AIDED CIVIL AND INFRASTRUCTURE ENGINEERING, Issue 2 2010
Yichang (James) Tsai
However, collecting such data is time-consuming, costly, and dangerous using traditional, manual surveying methods. It is especially difficult to perform such manual measurement when roadways have high traffic volumes. Thus, it would be valuable for transportation agencies if roadway curvature data could be computed from photographic images taken using low-cost digital cameras. This is the first article that develops an algorithm using emerging vision technology to acquire horizontal roadway curvature data from roadway images to perform roadway safety assessment. The proposed algorithm consists of four steps: (1) curve edges image processing, (2) mapping edge positions from an image domain to the real-world domain, (3) calibrating camera parameters, and (4) calculating the curve radius and center from curve points. The proposed algorithm was tested on roadways having various levels of curves and using different image sources to demonstrate its capability. The ground truth curvatures for two cases were also collected to evaluate the error of the proposed algorithm. The test results are very promising, and the computed curvatures are especially accurate for curves of small radii (less than 66 m/200 ft) with less than 1.0% relative errors with respect to the ground truth data. The proposed algorithm can be used as an alternative method that complements the traditional measurement methods used by state DOTs to collect roadway curvature data. [source]

Evaluation of a digital camera image applied to PCB inspection

HUMAN FACTORS AND ERGONOMICS IN MANUFACTURING & SERVICE INDUSTRIES, Issue 4 2008
Bernard C. Jiang
Rapid advancement and widespread digital camera applications have made it possible to replace charge-coupled device (CCD) cameras in automatic inspections for industrial applications. However, most digital camera applications using the automatic exposure mode may not be effective in some of the inspection environments. The reflection from a board surface in printed circuit board (PCB) inspections is one such problem area. The objective of this study is to develop a methodology to evaluate the effectiveness of using digital cameras for inspection. The indices used for evaluating digital camera image quality are the perceived image quality, the visual resolution, and the noise. An experiment was designed and conducted to determine the optimal camera parameter combination for attaining the best image quality. The desirability function was used to compare various digital camera parameter settings in considering three image quality indices for selecting the best camera-operating conditions. Based on the developed model and the subjective image quality index, the overall image quality improved 9.4% and 13.86%, respectively. The developed methodology can be used to: (a) determine the digital camera image quality, (b) provide an improved model for determining the automatic exposure setting for digital camera designers, and (c) adjust the digital camera parameters for automatic inspection. © 2008 Wiley Periodicals, Inc. [source]