568 research outputs found
High-Precision Localization Using Ground Texture
Location-aware applications play an increasingly critical role in everyday
life. However, satellite-based localization (e.g., GPS) has limited accuracy
and can be unusable in dense urban areas and indoors. We introduce an
image-based global localization system that is accurate to a few millimeters
and performs reliable localization both indoors and outside. The key idea is to
capture and index distinctive local keypoints in ground textures. This is based
on the observation that ground textures including wood, carpet, tile, concrete,
and asphalt may look random and homogeneous, but all contain cracks, scratches,
or unique arrangements of fibers. These imperfections are persistent, and can
serve as local features. Our system incorporates a downward-facing camera to
capture the fine texture of the ground, together with an image processing
pipeline that locates the captured texture patch in a compact database
constructed offline. We demonstrate the capability of our system to robustly,
accurately, and quickly locate test images on various types of outdoor and
indoor ground surfaces
Scan registration for autonomous mining vehicles using 3D-NDT
Scan registration is an essential subtask when building maps based on range finder data from mobile robots. The problem is to deduce how the robot has moved between consecutive scans, based on the shape of overlapping portions of the scans. This paper presents a new algorithm for registration of 3D data. The algorithm is a generalization and improvement of the normal distributions transform (NDT) for 2D data developed by Biber and Strasser, which allows for accurate registration using a memory-efficient representation of the scan surface. A detailed quantitative and qualitative comparison of the new algorithm with the 3D version of the popular ICP (iterative closest point) algorithm is presented. Results with actual mine data, some of which were collected with a new prototype 3D laser scanner, show that the presented algorithm is faster and slightly more reliable than the standard ICP algorithm for 3D registration, while using a more memory efficient scan surface representation
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Computational Light Routing: 3D Printed Optical Fibers for Sensing and Display
Despite recent interest in digital fabrication, there are still few algorithms that provide control over how light propagates inside a solid object. Existing methods either work only on the surface or restrict themselves to light diffusion in volumes. We use multi-material 3D printing to fabricate objects with embedded optical fibers, exploiting total internal reflection to guide light inside an object. We introduce automatic fiber design algorithms together with new manufacturing techniques to route light between two arbitrary surfaces. Our implicit algorithm optimizes light transmission by minimizing fiber curvature and maximizing fiber separation while respecting constraints such as fiber arrival angle. We also discuss the influence of different printable materials and fiber geometry on light propagation in the volume and the light angular distribution when exiting the fiber. Our methods enable new applications such as surface displays of arbitrary shape, touch-based painting of surfaces, and sensing a hemispherical light distribution in a single shot.National Science Foundation (U.S.) (Grant CCF-1012147)National Science Foundation (U.S.) (Grant IIS-1116296)United States. Defense Advanced Research Projects Agency (Grant N66001-12-1-4242)Intel Corporation (Science and Technology Center for Visual Computing)Alfred P. Sloan Foundation (Sloan Research Fellowship
Constructing Printable Surfaces with View-Dependent Appearance
We present a method for the digital fabrication of surfaces whose appearance
varies based on viewing direction. The surfaces are constructed from a mesh of
bars arranged in a self-occluding colored heightfield that creates the desired
view-dependent effects. At the heart of our method is a novel and simple
differentiable rendering algorithm specifically designed to render colored 3D
heightfields and enable efficient calculation of the gradient of appearance
with respect to heights and colors. This algorithm forms the basis of a
coarse-to-fine ML-based optimization process that adjusts the heights and
colors of the strips to minimize the loss between the desired and real surface
appearance from each viewpoint, deriving meshes that can then be fabricated
using a 3D printer. Using our method, we demonstrate both synthetic and
real-world fabricated results with view-dependent appearance.Comment: 10 pages, 16 figure
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Chopper: Partitioning models into 3D-printable parts
3D printing technology is rapidly maturing and becoming ubiquitous. One of the remaining obstacles to wide-scale adoption is that the object to be printed must fit into the working volume of the 3D printer. We propose a framework, called Chopper, to decompose a large 3D object into smaller parts so that each part fits into the printing volume. These parts can then be assembled to form the original object. We formulate a number of desirable criteria for the partition, including assemblability, having few components, unobtrusiveness of the seams, and structural soundness. Chopper optimizes these criteria and generates a partition either automatically or with user guidance. Our prototype outputs the final decomposed parts with customized connectors on the interfaces. We demonstrate the effectiveness of Chopper on a variety of non-trivial real-world objects.National Science Foundation (U.S.) (Grant CCF-1012147)National Science Foundation (U.S.) (Grant IIS-1116296)Intel Corporation (Science and Technology Center for Visual Computing
Clutter Detection and Removal in 3D Scenes with View-Consistent Inpainting
Removing clutter from scenes is essential in many applications, ranging from
privacy-concerned content filtering to data augmentation. In this work, we
present an automatic system that removes clutter from 3D scenes and inpaints
with coherent geometry and texture. We propose techniques for its two key
components: 3D segmentation from shared properties and 3D inpainting, both of
which are important problems. The definition of 3D scene clutter
(frequently-moving objects) is not well captured by commonly-studied object
categories in computer vision. To tackle the lack of well-defined clutter
annotations, we group noisy fine-grained labels, leverage virtual rendering,
and impose an instance-level area-sensitive loss. Once clutter is removed, we
inpaint geometry and texture in the resulting holes by merging inpainted RGB-D
images. This requires novel voting and pruning strategies that guarantee
multi-view consistency across individually inpainted images for mesh
reconstruction. Experiments on ScanNet and Matterport dataset show that our
method outperforms baselines for clutter segmentation and 3D inpainting, both
visually and quantitatively.Comment: 18 pages. ICCV 2023. Project page:
https://weify627.github.io/clutter
Hand Pose Estimation with Mems-Ultrasonic Sensors
Hand tracking is an important aspect of human-computer interaction and has a
wide range of applications in extended reality devices. However, current hand
motion capture methods suffer from various limitations. For instance,
visual-based hand pose estimation is susceptible to self-occlusion and changes
in lighting conditions, while IMU-based tracking gloves experience significant
drift and are not resistant to external magnetic field interference. To address
these issues, we propose a novel and low-cost hand-tracking glove that utilizes
several MEMS-ultrasonic sensors attached to the fingers, to measure the
distance matrix among the sensors. Our lightweight deep network then
reconstructs the hand pose from the distance matrix. Our experimental results
demonstrate that this approach is both accurate, size-agnostic, and robust to
external interference. We also show the design logic for the sensor selection,
sensor configurations, circuit diagram, as well as model architecture
Gradient-Based Dovetail Joint Shape Optimization for Stiffness
It is common to manufacture an object by decomposing it into parts that can
be assembled. This decomposition is often required by size limits of the
machine, the complex structure of the shape, etc. To make it possible to easily
assemble the final object, it is often desirable to design geometry that
enables robust connections between the subcomponents. In this project, we study
the task of dovetail-joint shape optimization for stiffness using
gradient-based optimization. This optimization requires a differentiable
simulator that is capable of modeling the contact between the two parts of a
joint, making it possible to reason about the gradient of the stiffness with
respect to shape parameters. Our simulation approach uses a penalty method that
alternates between optimizing each side of the joint, using the adjoint method
to compute gradients. We test our method by optimizing the joint shapes in
three different joint shape spaces, and evaluate optimized joint shapes in both
simulation and real-world tests. The experiments show that optimized joint
shapes achieve higher stiffness, both synthetically and in real-world tests.Comment: ACM SCF 2023: Proceedings of the 8th Annual ACM Symposium on
Computational Fabricatio
Executing Multidatabase Transactions
In a multidatabase environment, the traditional transaction model has been found to be too restrictive. Therefore, several extended transaction models have been proposed in which some of the requirements of transaction, such as isolation or atomicity, are optional. The authors describe one of such extensions, the flexible transaction model and discuss the scheduling of transactions involving multiple autonomous database systems managed by heterogeneous DBMS.
The scheduling algorithm for flexible transactions is implemented using L.0, a logically parallel language which provides a framework for concisely specifying the multidatabase transactions and for scheduling them. The key aspects of a flexible transaction specification, such as subtransaction execution dependencies and transaction success criteria, can be naturally represented in L.0. Furthermore, scheduling in L.0 achieves maximal parallelism allowed by the specifications of transactions, which results in the improvement of their response times.
To provide access to multiple heterogeneous hardware and software systems, they use the Distributed Operation Language (DOL). DOL approach is based on providing a common communication and data exchange protocol and uses local access managers to protect the autonomy of member software systems. When L.0 determines that a subtransaction is ready to execute, it hands it through an interface to the DOL system for execution. The interface between L.0 and DOL provides the former with the execution status of subtransactions
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