Kaleem Siddiqi

openreview.net

Shape-Based Measures Improve Scene Categorization

Morteza Rezanejad

John Wilder

Dirk B. Walther

Allan D. Jepson

Sven Dickinson

Converging evidence indicates that deep neural network models that are trained on large datasets are biased toward color and texture informa… (see more)tion. Humans, on the other hand, can easily recognize objects and scenes from images as well as from bounding contours. Mid-level vision is characterized by the recombination and organization of simple primary features into more complex ones by a set of so-called Gestalt grouping rules. While described qualitatively in the human literature, a computational implementation of these perceptual grouping rules is so far missing. In this article, we contribute a novel set of algorithms for the detection of contour-based cues in complex scenes. We use the medial axis transform (MAT) to locally score contours according to these grouping rules. We demonstrate the benefit of these cues for scene categorization in two ways: (i) Both human observers and CNN models categorize scenes most accurately when perceptual grouping information is emphasized. (ii) Weighting the contours with these measures boosts performance of a CNN model significantly compared to the use of unweighted contours. Our work suggests that, even though these measures are computed directly from contours in the image, current CNN models do not appear to extract or utilize these grouping cues.

2023-12-01

IEEE Transactions on Pattern Analysis and Machine Intelligence (published)

Multimodal and Force-Matched Imitation Learning with a See-Through Visuotactile Sensor

Trevor Ablett

Oliver Limoyo

Adam Sigal

Affan Jilani

Jonathan Kelly

Francois R. Hogan

Gregory Dudek

Kinesthetic Teaching is a popular approach to collecting expert robotic demonstrations of contact-rich tasks for imitation learning (IL), bu… (see more)t it typically only measures motion, ignoring the force placed on the environment by the robot. Furthermore, contact-rich tasks require accurate sensing of both reaching and touching, which can be difficult to provide with conventional sensing modalities. We address these challenges with a See-Through-your-Skin (STS) visuotactile sensor, using the sensor both (i) as a measurement tool to improve kinesthetic teaching, and (ii) as a policy input in contact-rich door manipulation tasks. An STS sensor can be switched between visual and tactile modes by leveraging a semi-transparent surface and controllable lighting, allowing for both pre-contact visual sensing and during-contact tactile sensing with a single sensor. First, we propose tactile force matching, a methodology that enables a robot to match forces read during kinesthetic teaching using tactile signals. Second, we develop a policy that controls STS mode switching, allowing a policy to learn the appropriate moment to switch an STS from its visual to its tactile mode. Finally, we study multiple observation configurations to compare and contrast the value of visual and tactile data from an STS with visual data from a wrist-mounted eye-in-hand camera. With over 3,000 test episodes from real-world manipulation experiments, we find that the inclusion of force matching raises average policy success rates by 62.5%, STS mode switching by 30.3%, and STS data as a policy input by 42.5%. Our results highlight the utility of see-through tactile sensing for IL, both for data collection to allow force matching, and for policy execution to allow accurate task feedback.

2023-11-02

ArXiv (preprint)

Cardiomyocyte orientation recovery at micrometer scale reveals long‐axis fiber continuum in heart walls

Drisya Dileep

Tabish A Syed

Tyler FW Sloan

Perundurai S Dhandapany

Minhajuddin Sirajuddin

2023-09-06

The EMBO Journal (published)

MLGCN: An Ultra Efficient Graph Convolution Neural Model For 3D Point Cloud Analysis

Mohammad Khodadad

Morteza Rezanejad

Ali Shiraee Kasmaee

Dirk Bernhardt-Walther

Hamidreza Mahyar

2023-03-31

ArXiv (preprint)

Organizing Principles of Astrocytic Nanoarchitecture in the Mouse Cerebral Cortex

Christopher K. Salmon

Tabish A Syed

J. Benjamin Kacerovsky

Nensi Alivodej

Alexandra L. Schober

Tyler F. W. Sloan

Michael T. Pratte

Michael P. Rosen

Miranda Green

Adario DasGupta

Shaurya Mehta

Affan Jilani

Yanan Wang

Hojatollah Vali

Craig A. Mandato

Keith K. Murai

2023-02-01

Current Biology (published)

Ultrastructure Analysis of Cardiomyocytes and Their Nuclei

Tabish A Syed

Yanan Wang

Drisya Dileep

Minhajuddin Sirajuddin

2023-01-01

Functional Imaging and Modeling of the Heart (published)

Predicting histopathology markers of endometrial carcinoma with a quantitative image analysis approach based on spherical harmonics in multiparametric MRI.

Thierry L. Lefebvre

Ozan Ciga

Sahir Rai Bhatnagar

Yoshiko Ueno

S. Saif

Eric Winter-Reinhold

Anthony Dohan

P. Soyer

Reza Forghani

Jan Seuntjens

Caroline Reinhold

Peter Savadjiev

2022-10-01

Diagnostic and Interventional Imaging (published)

Medial Spectral Coordinates for 3D Shape Analysis

Morteza Rezanejad

Mohammad Khodadad

Hamidreza Mahyar

Hervé Lombaert

Michael Gruninger

Dirk B. Walther

In recent years there has been a resurgence of interest in our community in the shape analysis of 3D objects repre-sented by surface meshes,… (see more) their voxelized interiors, or surface point clouds. In part, this interest has been stimulated by the increased availability of RGBD cameras, and by applications of computer vision to autonomous driving, medical imaging, and robotics. In these settings, spectral co-ordinates have shown promise for shape representation due to their ability to incorporate both local and global shape properties in a manner that is qualitatively invariant to iso-metric transformations. Yet, surprisingly, such coordinates have thus far typically considered only local surface positional or derivative information. In the present article, we propose to equip spectral coordinates with medial (object width) information, so as to enrich them. The key idea is to couple surface points that share a medial ball, via the weights of the adjacency matrix. We develop a spectral feature using this idea, and the algorithms to compute it. The incorporation of object width and medial coupling has direct benefits, as illustrated by our experiments on object classification, object part segmentation, and surface point correspondence.

2022-06-18

2022 IEEE/CVF Conference on Computer Vision and Pattern Recognition (CVPR) (published)

Neural correlates of local parallelism during naturalistic vision

John Wilder

Morteza Rezanejad

Sven Dickinson

Allan Jepson

Dirk B. Walther

Human observers can rapidly perceive complex real-world scenes. Grouping visual elements into meaningful units is an integral part of this p… (see more)rocess. Yet, so far, the neural underpinnings of perceptual grouping have only been studied with simple lab stimuli. We here uncover the neural mechanisms of one important perceptual grouping cue, local parallelism. Using a new, image-computable algorithm for detecting local symmetry in line drawings and photographs, we manipulated the local parallelism content of real-world scenes. We decoded scene categories from patterns of brain activity obtained via functional magnetic resonance imaging (fMRI) in 38 human observers while they viewed the manipulated scenes. Decoding was significantly more accurate for scenes containing strong local parallelism compared to weak local parallelism in the parahippocampal place area (PPA), indicating a central role of parallelism in scene perception. To investigate the origin of the parallelism signal we performed a model-based fMRI analysis of the public BOLD5000 dataset, looking for voxels whose activation time course matches that of the locally parallel content of the 4916 photographs viewed by the participants in the experiment. We found a strong relationship with average local symmetry in visual areas V1-4, PPA, and retrosplenial cortex (RSC). Notably, the parallelism-related signal peaked first in V4, suggesting V4 as the site for extracting paralleism from the visual input. We conclude that local parallelism is a perceptual grouping cue that influences neuronal activity throughout the visual hierarchy, presumably starting at V4. Parallelism plays a key role in the representation of scene categories in PPA.

2022-01-21

PLoS ONE (published)

Neural correlates of local parallelism during naturalistic vision

John Wilder

Morteza Rezanejad

Sven J. Dickinson

A. Jepson

Dirk. B. Walther

Human observers can rapidly perceive complex real-world scenes. Grouping visual elements into meaningful units is an integral part of this p… (see more)rocess. Yet, so far, the neural underpinnings of perceptual grouping have only been studied with simple lab stimuli. We here uncover the neural mechanisms of one important perceptual grouping cue, local parallelism. Using a new, image-computable algorithm for detecting local symmetry in line drawings and photographs, we manipulated the local parallelism content of real-world scenes. We decoded scene categories from patterns of brain activity obtained via functional magnetic resonance imaging (fMRI) in 38 human observers while they viewed the manipulated scenes. Decoding was significantly more accurate for scenes containing strong local parallelism compared to weak local parallelism in the parahippocampal place area (PPA), indicating a central role of parallelism in scene perception. To investigate the origin of the parallelism signal we performed a model-based fMRI analysis of the public BOLD5000 dataset, looking for voxels whose activation time course matches that of the locally parallel content of the 4916 photographs viewed by the participants in the experiment. We found a strong relationship with average local symmetry in visual areas V1-4, PPA, and retrosplenial cortex (RSC). Notably, the parallelism-related signal peaked first in V4, suggesting V4 as the site for extracting paralleism from the visual input. We conclude that local parallelism is a perceptual grouping cue that influences neuronal activity throughout the visual hierarchy, presumably starting at V4. Parallelism plays a key role in the representation of scene categories in PPA.

2022-01-21

PLoS ONE (published)

Medial Spectral Coordinates for 3D Shape Analysis

Morteza Rezanejad

Mohammad Khodadad

H. Mahyar

Hervé Lombaert

M. Gruninger

Dirk. B. Walther

In recent years there has been a resurgence of interest in our community in the shape analysis of 3D objects repre-sented by surface meshes,… (see more) their voxelized interiors, or surface point clouds. In part, this interest has been stimulated by the increased availability of RGBD cameras, and by applications of computer vision to autonomous driving, medical imaging, and robotics. In these settings, spectral co-ordinates have shown promise for shape representation due to their ability to incorporate both local and global shape properties in a manner that is qualitatively invariant to iso-metric transformations. Yet, surprisingly, such coordinates have thus far typically considered only local surface positional or derivative information. In the present article, we propose to equip spectral coordinates with medial (object width) information, so as to enrich them. The key idea is to couple surface points that share a medial ball, via the weights of the adjacency matrix. We develop a spectral feature using this idea, and the algorithms to compute it. The incorporation of object width and medial coupling has direct benefits, as illustrated by our experiments on object classification, object part segmentation, and surface point correspondence.

2021-11-26

ArXiv (preprint)