Search Results for author: Fredrik Kahl

Found 36 papers, 15 papers with code

Back to the Feature: Learning Robust Camera Localization from Pixels to Pose

2 code implementations CVPR 2021 Paul-Edouard Sarlin, Ajaykumar Unagar, Måns Larsson, Hugo Germain, Carl Toft, Viktor Larsson, Marc Pollefeys, Vincent Lepetit, Lars Hammarstrand, Fredrik Kahl, Torsten Sattler

In this paper, we go Back to the Feature: we argue that deep networks should focus on learning robust and invariant visual features, while the geometric estimation should be left to principled algorithms.

Camera Localization Metric Learning +1

Fine-Grained Segmentation Networks: Self-Supervised Segmentation for Improved Long-Term Visual Localization

1 code implementation18 Aug 2019 Måns Larsson, Erik Stenborg, Carl Toft, Lars Hammarstrand, Torsten Sattler, Fredrik Kahl

In this paper, we propose a new neural network, the Fine-Grained Segmentation Network (FGSN), that can be used to provide image segmentations with a larger number of labels and can be trained in a self-supervised fashion.

Autonomous Driving Segmentation +1

A case for using rotation invariant features in state of the art feature matchers

1 code implementation21 Apr 2022 Georg Bökman, Fredrik Kahl

The aim of this paper is to demonstrate that a state of the art feature matcher (LoFTR) can be made more robust to rotations by simply replacing the backbone CNN with a steerable CNN which is equivariant to translations and image rotations.

Single-Image Depth Prediction Makes Feature Matching Easier

1 code implementation21 Aug 2020 Carl Toft, Daniyar Turmukhambetov, Torsten Sattler, Fredrik Kahl, Gabriel Brostow

Good local features improve the robustness of many 3D re-localization and multi-view reconstruction pipelines.

Depth Estimation Depth Prediction

A Cross-Season Correspondence Dataset for Robust Semantic Segmentation

1 code implementation16 Mar 2019 Måns Larsson, Erik Stenborg, Lars Hammarstrand, Torsten Sattler, Mark Pollefeys, Fredrik Kahl

We show that adding the correspondences as extra supervision during training improves the segmentation performance of the convolutional neural network, making it more robust to seasonal changes and weather conditions.

Segmentation Semantic Segmentation

How Privacy-Preserving are Line Clouds? Recovering Scene Details from 3D Lines

1 code implementation CVPR 2021 Kunal Chelani, Fredrik Kahl, Torsten Sattler

To address the resulting potential privacy risks for user-generated content, it was recently proposed to lift point clouds to line clouds by replacing 3D points by randomly oriented 3D lines passing through these points.

Pose Estimation Privacy Preserving +2

Steerers: A framework for rotation equivariant keypoint descriptors

1 code implementation4 Dec 2023 Georg Bökman, Johan Edstedt, Michael Felsberg, Fredrik Kahl

Image keypoint descriptions that are discriminative and matchable over large changes in viewpoint are vital for 3D reconstruction.

3D Reconstruction Data Augmentation

Improving Open-Set Semi-Supervised Learning with Self-Supervision

1 code implementation24 Jan 2023 Erik Wallin, Lennart Svensson, Fredrik Kahl, Lars Hammarstrand

Open-set semi-supervised learning (OSSL) embodies a practical scenario within semi-supervised learning, wherein the unlabeled training set encompasses classes absent from the labeled set.

Open Set Learning

Investigating how ReLU-networks encode symmetries

1 code implementation NeurIPS 2023 Georg Bökman, Fredrik Kahl

These experiments are not only of interest for understanding how group equivariance is encoded in ReLU-networks, but they also give a new perspective on Entezari et al.'s permutation conjecture as we find that it is typically easier to merge a network with a group-transformed version of itself than merging two different networks.

Privacy-Preserving Representations are not Enough -- Recovering Scene Content from Camera Poses

1 code implementation8 May 2023 Kunal Chelani, Torsten Sattler, Fredrik Kahl, Zuzana Kukelova

In this paper, we show that an attacker can learn about details of a scene without any access by simply querying a localization service.

Privacy Preserving Visual Localization

A Projected Gradient Descent Method for CRF Inference allowing End-To-End Training of Arbitrary Pairwise Potentials

no code implementations24 Jan 2017 Måns Larsson, Anurag Arnab, Fredrik Kahl, Shuai Zheng, Philip Torr

It is empirically demonstrated that such learned potentials can improve segmentation accuracy and that certain label class interactions are indeed better modelled by a non-Gaussian potential.

Segmentation Semantic Segmentation +1

Rotation Averaging and Strong Duality

no code implementations CVPR 2018 Anders Eriksson, Carl Olsson, Fredrik Kahl, Tat-Jun Chin

In this paper we explore the role of duality principles within the problem of rotation averaging, a fundamental task in a wide range of computer vision applications.

Multiresolution Search of the Rigid Motion Space for Intensity Based Registration

no code implementations14 Oct 2015 Behrooz Nasihatkon, Fredrik Kahl

Our results show that low resolution target values can tightly bound the high-resolution target function in natural images.

Image Registration

Minimal Solvers for Relative Pose with a Single Unknown Radial Distortion

no code implementations CVPR 2014 Yubin Kuang, Jan E. Solem, Fredrik Kahl, Kalle Astrom

In this paper, we study the problems of estimating relative pose between two cameras in the presence of radial distortion.

Semantic Match Consistency for Long-Term Visual Localization

no code implementations ECCV 2018 Carl Toft, Erik Stenborg, Lars Hammarstrand, Lucas Brynte, Marc Pollefeys, Torsten Sattler, Fredrik Kahl

Robust and accurate visual localization across large appearance variations due to changes in time of day, seasons, or changes of the environment is a challenging problem which is of importance to application areas such as navigation of autonomous robots.

Visual Localization

Optimal Geometric Fitting under the Truncated L2-Norm

no code implementations CVPR 2013 Erik Ask, Olof Enqvist, Fredrik Kahl

First, it is shown that for a large class of problems, the statistically more desirable truncated L 2 -norm can be optimized with the same complexity.

Accurate Localization and Pose Estimation for Large 3D Models

no code implementations CVPR 2014 Linus Svarm, Olof Enqvist, Magnus Oskarsson, Fredrik Kahl

For one, it makes the correspondence problem very difficult and it is likely that there will be a significant rate of outliers to handle.

Pose Estimation

Fast and Reliable Two-View Translation Estimation

no code implementations CVPR 2014 Johan Fredriksson, Olof Enqvist, Fredrik Kahl

It has long been recognized that one of the fundamental difficulties in theestimation of two-view epipolar geometry is the capability of handling outliers.

Motion Estimation Translation +1

Optimal Relative Pose With Unknown Correspondences

no code implementations CVPR 2016 Johan Fredriksson, Viktor Larsson, Carl Olsson, Fredrik Kahl

Previous work on estimating the epipolar geometry of two views relies on being able to reliably match feature points based on appearance.

Minimizing the Maximal Rank

no code implementations CVPR 2016 Erik Bylow, Carl Olsson, Fredrik Kahl, Mikael Nilsson

In the latter case, matrices are divided into sub-matrices and the envelope is computed for each sub-block individually.

Denoising

Globally Optimal Rigid Intensity Based Registration: A Fast Fourier Domain Approach

no code implementations CVPR 2016 Behrooz Nasihatkon, Frida Fejne, Fredrik Kahl

In this paper, we propose a dual algorithm in which the optimization is done in the Fourier domain, and multiple resolution levels are replaced by multiple frequency bands.

Monocular 3D Object Detection and Box Fitting Trained End-to-End Using Intersection-over-Union Loss

no code implementations19 Jun 2019 Eskil Jörgensen, Christopher Zach, Fredrik Kahl

We show how modeling heteroscedastic uncertainty improves performance upon our baseline, and furthermore, how back-propagation can be done through the optimizer in order to train the pipeline end-to-end for additional accuracy.

Autonomous Driving Monocular 3D Object Detection +2

Pose Proposal Critic: Robust Pose Refinement by Learning Reprojection Errors

no code implementations BMVC 2020 Lucas Brynte, Fredrik Kahl

In recent years, considerable progress has been made for the task of rigid object pose estimation from a single RGB-image, but achieving robustness to partial occlusions remains a challenging problem.

6D Pose Estimation using RGB

Azimuthal Rotational Equivariance in Spherical CNNs

no code implementations1 Jan 2021 Carl Toft, Georg Bökman, Fredrik Kahl

In this work, we analyze linear operators from $L^2(S^2) \rightarrow L^2(S^2)$ which are equivariant to azimuthal rotations, that is, rotations around the z-axis.

On the Tightness of Semidefinite Relaxations for Rotation Estimation

no code implementations6 Jan 2021 Lucas Brynte, Viktor Larsson, José Pedro Iglesias, Carl Olsson, Fredrik Kahl

In studying the empirical performance we note that there are few failure cases reported in the literature, in particular for estimation problems with a single rotation, motivating us to gain further theoretical understanding.

A Quasiconvex Formulation for Radial Cameras

no code implementations CVPR 2021 Carl Olsson, Viktor Larsson, Fredrik Kahl

In this paper we study structure from motion problems for 1D radial cameras.

CrowdDriven: A New Challenging Dataset for Outdoor Visual Localization

no code implementations ICCV 2021 Ara Jafarzadeh, Manuel Lopez Antequera, Pau Gargallo, Yubin Kuang, Carl Toft, Fredrik Kahl, Torsten Sattler

Visual localization is the problem of estimating the position and orientation from which a given image (or a sequence of images) is taken in a known scene.

Benchmarking Self-Driving Cars +1

Rigidity Preserving Image Transformations and Equivariance in Perspective

no code implementations31 Jan 2022 Lucas Brynte, Georg Bökman, Axel Flinth, Fredrik Kahl

We characterize the class of image plane transformations which realize rigid camera motions and call these transformations `rigidity preserving'.

6D Pose Estimation using RGB Inductive Bias +1

In Search of Projectively Equivariant Networks

1 code implementation29 Sep 2022 Georg Bökman, Axel Flinth, Fredrik Kahl

Equivariance of linear neural network layers is well studied.

Adjustable Visual Appearance for Generalizable Novel View Synthesis

no code implementations2 Jun 2023 Josef Bengtson, David Nilsson, Che-Tsung Lin, Marcel Büsching, Fredrik Kahl

We present a generalizable novel view synthesis method which enables modifying the visual appearance of an observed scene so rendered views match a target weather or lighting condition without any scene specific training or access to reference views at the target condition.

Generalizable Novel View Synthesis Novel View Synthesis +1

Learning Structure-from-Motion with Graph Attention Networks

no code implementations30 Aug 2023 Lucas Brynte, José Pedro Iglesias, Carl Olsson, Fredrik Kahl

In this paper we tackle the problem of learning Structure-from-Motion (SfM) through the use of graph attention networks.

Graph Attention Pose Estimation

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