Understanding and predicting where people look in images

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2011.Cataloged from PDF version of thesis.Includes bibliographical references (p. 115-126).For many applications in graphics, design, and human computer interaction, it is essential to understand where humans look in a scene. This is a challenging task given that no one fully understands how the human visual system works. This thesis explores the way people look at different types of images and provides methods of predicting where they look in new scenes. We describe a new way to model where people look from ground truth eye tracking data using techniques of machine learning that outperforms all existing models, and provide a benchmark data set to quantitatively compare existing and future models. In addition we explore how image resolution affects where people look. Our experiments, models, and large eye tracking data sets should help future researchers better understand and predict where people look in order to create more powerful computational vision systems.by Tilke Judd.Ph.D

Apparent ridges for line drawing

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2007.Includes bibliographical references (p. 69-72).Non-photorealistic line drawing depicts 3D shapes through the rendering of feature lines. A number of characterizations of relevant lines have been proposed but none of these definitions alone seem to capture all visually-relevant lines. We introduce a new definition of feature lines based on two perceptual observations. First, human perception is sensitive to the variation of shading, and since shape perception is little affected by lighting and reflectance modification, we should focus on normal variation. Second, view-dependent lines better convey the shape of smooth surfaces better than view-independent lines. From this we define view-dependent curvature as the variation of the surface normal with respect to a viewing screen plane, and apparent ridges as the locus points of the maximum of the view-dependent curvature. We derive the equation for apparent ridges and present a new algorithm to render line drawings of 3D meshes. We show that our apparent ridges encompass or enhance aspects of several other feature lines.by Tilke Judd.S.M

A Benchmark of Computational Models of Saliency to Predict Human Fixations

Many computational models of visual attention have been created from a wide variety of different approaches to predict where people look in images. Each model is usually introduced by demonstrating performances on new images, and it is hard to make immediate comparisons between models. To alleviate this problem, we propose a benchmark data set containing 300 natural images with eye tracking data from 39 observers to compare model performances. We calculate the performance of 10 models at predicting ground truth fixations using three different metrics. We provide a way for people to submit new models for evaluation online. We find that the Judd et al. and Graph-based visual saliency models perform best. In general, models with blurrier maps and models that include a center bias perform well. We add and optimize a blur and center bias for each model and show improvements. We compare performances to baseline models of chance, center and human performance. We show that human performance increases with the number of humans to a limit. We analyze the similarity of different models using multidimensional scaling and explore the relationship between model performance and fixation consistency. Finally, we offer observations about how to improve saliency models in the future