5,609 research outputs found
A clever elimination strategy for efficient minimal solvers
We present a new insight into the systematic generation of minimal solvers in
computer vision, which leads to smaller and faster solvers. Many minimal
problem formulations are coupled sets of linear and polynomial equations where
image measurements enter the linear equations only. We show that it is useful
to solve such systems by first eliminating all the unknowns that do not appear
in the linear equations and then extending solutions to the rest of unknowns.
This can be generalized to fully non-linear systems by linearization via
lifting. We demonstrate that this approach leads to more efficient solvers in
three problems of partially calibrated relative camera pose computation with
unknown focal length and/or radial distortion. Our approach also generates new
interesting constraints on the fundamental matrices of partially calibrated
cameras, which were not known before.Comment: 13 pages, 7 figure
Beyond Gr\"obner Bases: Basis Selection for Minimal Solvers
Many computer vision applications require robust estimation of the underlying
geometry, in terms of camera motion and 3D structure of the scene. These robust
methods often rely on running minimal solvers in a RANSAC framework. In this
paper we show how we can make polynomial solvers based on the action matrix
method faster, by careful selection of the monomial bases. These monomial bases
have traditionally been based on a Gr\"obner basis for the polynomial ideal.
Here we describe how we can enumerate all such bases in an efficient way. We
also show that going beyond Gr\"obner bases leads to more efficient solvers in
many cases. We present a novel basis sampling scheme that we evaluate on a
number of problems
Calibration Wizard: A Guidance System for Camera Calibration Based on Modelling Geometric and Corner Uncertainty
It is well known that the accuracy of a calibration depends strongly on the
choice of camera poses from which images of a calibration object are acquired.
We present a system -- Calibration Wizard -- that interactively guides a user
towards taking optimal calibration images. For each new image to be taken, the
system computes, from all previously acquired images, the pose that leads to
the globally maximum reduction of expected uncertainty on intrinsic parameters
and then guides the user towards that pose. We also show how to incorporate
uncertainty in corner point position in a novel principled manner, for both,
calibration and computation of the next best pose. Synthetic and real-world
experiments are performed to demonstrate the effectiveness of Calibration
Wizard.Comment: Oral presentation at ICCV 201
MLPnP - A Real-Time Maximum Likelihood Solution to the Perspective-n-Point Problem
In this paper, a statistically optimal solution to the Perspective-n-Point
(PnP) problem is presented. Many solutions to the PnP problem are geometrically
optimal, but do not consider the uncertainties of the observations. In
addition, it would be desirable to have an internal estimation of the accuracy
of the estimated rotation and translation parameters of the camera pose. Thus,
we propose a novel maximum likelihood solution to the PnP problem, that
incorporates image observation uncertainties and remains real-time capable at
the same time. Further, the presented method is general, as is works with 3D
direction vectors instead of 2D image points and is thus able to cope with
arbitrary central camera models. This is achieved by projecting (and thus
reducing) the covariance matrices of the observations to the corresponding
vector tangent space.Comment: Submitted to the ISPRS congress (2016) in Prague. Oral Presentation.
Published in ISPRS Ann. Photogramm. Remote Sens. Spatial Inf. Sci., III-3,
131-13
A sparse resultant based method for efficient minimal solvers
Many computer vision applications require robust and efficient estimation of
camera geometry. The robust estimation is usually based on solving camera
geometry problems from a minimal number of input data measurements, i.e.
solving minimal problems in a RANSAC framework. Minimal problems often result
in complex systems of polynomial equations. Many state-of-the-art efficient
polynomial solvers to these problems are based on Gr\"obner bases and the
action-matrix method that has been automatized and highly optimized in recent
years. In this paper we study an alternative algebraic method for solving
systems of polynomial equations, i.e., the sparse resultant-based method and
propose a novel approach to convert the resultant constraint to an eigenvalue
problem. This technique can significantly improve the efficiency and stability
of existing resultant-based solvers. We applied our new resultant-based method
to a large variety of computer vision problems and show that for most of the
considered problems, the new method leads to solvers that are the same size as
the the best available Gr\"obner basis solvers and of similar accuracy. For
some problems the new sparse-resultant based method leads to even smaller and
more stable solvers than the state-of-the-art Gr\"obner basis solvers. Our new
method can be fully automatized and incorporated into existing tools for
automatic generation of efficient polynomial solvers and as such it represents
a competitive alternative to popular Gr\"obner basis methods for minimal
problems in computer vision
Computational Methods for Computer Vision : Minimal Solvers and Convex Relaxations
Robust fitting of geometric models is a core problem in computer vision. The most common approach is to use a hypothesize-and-test framework, such as RANSAC. In these frameworks the model is estimated from as few measurements as possible, which minimizes the risk of selecting corrupted measurements. These estimation problems are called minimal problems, and they can often be formulated as systems of polynomial equations. In this thesis we present new methods for building so-called minimal solvers or polynomial solvers, which are specialized code for solving such systems. On several minimal problems we improve on the state-of-the-art both with respect to numerical stability and execution time.In many computer vision problems low rank matrices naturally occur. The rank can serve as a measure of model complexity and typically a low rank is desired. Optimization problems containing rank penalties or constraints are in general difficult. Recently convex relaxations, such as the nuclear norm, have been used to make these problems tractable. In this thesis we present new convex relaxations for rank-based optimization which avoid drawbacks of previous approaches and provide tighter relaxations. We evaluate our methods on a number of real and synthetic datasets and show state-of-the-art results
Sparse resultant based minimal solvers in computer vision and their connection with the action matrix
Many computer vision applications require robust and efficient estimation of
camera geometry from a minimal number of input data measurements, i.e., solving
minimal problems in a RANSAC framework. Minimal problems are usually formulated
as complex systems of sparse polynomials. The systems usually are
overdetermined and consist of polynomials with algebraically constrained
coefficients. Most state-of-the-art efficient polynomial solvers are based on
the action matrix method that has been automated and highly optimized in recent
years. On the other hand, the alternative theory of sparse resultants and
Newton polytopes has been less successful for generating efficient solvers,
primarily because the polytopes do not respect the constraints on the
coefficients. Therefore, in this paper, we propose a simple iterative scheme to
test various subsets of the Newton polytopes and search for the most efficient
solver. Moreover, we propose to use an extra polynomial with a special form to
further improve the solver efficiency via a Schur complement computation. We
show that for some camera geometry problems our extra polynomial-based method
leads to smaller and more stable solvers than the state-of-the-art Grobner
basis-based solvers. The proposed method can be fully automated and
incorporated into existing tools for automatic generation of efficient
polynomial solvers. It provides a competitive alternative to popular Grobner
basis-based methods for minimal problems in computer vision. We also study the
conditions under which the minimal solvers generated by the state-of-the-art
action matrix-based methods and the proposed extra polynomial resultant-based
method, are equivalent. Specifically we consider a step-by-step comparison
between the approaches based on the action matrix and the sparse resultant,
followed by a set of substitutions, which would lead to equivalent minimal
solvers.Comment: arXiv admin note: text overlap with arXiv:1912.1026
- …