6,001 research outputs found
Progressive Transient Photon Beams
In this work we introduce a novel algorithm for transient rendering in
participating media. Our method is consistent, robust, and is able to generate
animations of time-resolved light transport featuring complex caustic light
paths in media. We base our method on the observation that the spatial
continuity provides an increased coverage of the temporal domain, and
generalize photon beams to transient-state. We extend the beam steady-state
radiance estimates to include the temporal domain. Then, we develop a
progressive version of spatio-temporal density estimations, that converges to
the correct solution with finite memory requirements by iteratively averaging
several realizations of independent renders with a progressively reduced kernel
bandwidth. We derive the optimal convergence rates accounting for space and
time kernels, and demonstrate our method against previous consistent transient
rendering methods for participating media
NeRRF: 3D Reconstruction and View Synthesis for Transparent and Specular Objects with Neural Refractive-Reflective Fields
Neural radiance fields (NeRF) have revolutionized the field of image-based
view synthesis. However, NeRF uses straight rays and fails to deal with
complicated light path changes caused by refraction and reflection. This
prevents NeRF from successfully synthesizing transparent or specular objects,
which are ubiquitous in real-world robotics and A/VR applications. In this
paper, we introduce the refractive-reflective field. Taking the object
silhouette as input, we first utilize marching tetrahedra with a progressive
encoding to reconstruct the geometry of non-Lambertian objects and then model
refraction and reflection effects of the object in a unified framework using
Fresnel terms. Meanwhile, to achieve efficient and effective anti-aliasing, we
propose a virtual cone supersampling technique. We benchmark our method on
different shapes, backgrounds and Fresnel terms on both real-world and
synthetic datasets. We also qualitatively and quantitatively benchmark the
rendering results of various editing applications, including material editing,
object replacement/insertion, and environment illumination estimation. Codes
and data are publicly available at https://github.com/dawning77/NeRRF
Reconstruction of hidden 3D shapes using diffuse reflections
We analyze multi-bounce propagation of light in an unknown hidden volume and
demonstrate that the reflected light contains sufficient information to recover
the 3D structure of the hidden scene. We formulate the forward and inverse
theory of secondary and tertiary scattering reflection using ideas from energy
front propagation and tomography. We show that using careful choice of
approximations, such as Fresnel approximation, greatly simplifies this problem
and the inversion can be achieved via a backpropagation process. We provide a
theoretical analysis of the invertibility, uniqueness and choices of
space-time-angle dimensions using synthetic examples. We show that a 2D streak
camera can be used to discover and reconstruct hidden geometry. Using a 1D high
speed time of flight camera, we show that our method can be used recover 3D
shapes of objects "around the corner"
Real-World Normal Map Capture for Nearly Flat Reflective Surfaces
Although specular objects have gained interest in recent
years, virtually no approaches exist for markerless reconstruction
of reflective scenes in the wild. In this work, we
present a practical approach to capturing normal maps in
real-world scenes using video only. We focus on nearly planar
surfaces such as windows, facades from glass or metal,
or frames, screens and other indoor objects and show how
normal maps of these can be obtained without the use of an
artificial calibration object. Rather, we track the reflections
of real-world straight lines, while moving with a hand-held
or vehicle-mounted camera in front of the object. In contrast
to error-prone local edge tracking, we obtain the reflections
by a robust, global segmentation technique of an
ortho-rectified 3D video cube that also naturally allows efficient
user interaction. Then, at each point of the reflective
surface, the resulting 2D-curve to 3D-line correspondence
provides a novel quadratic constraint on the local surface
normal. This allows to globally solve for the shape by integrability
and smoothness constraints and easily supports
the usage of multiple lines. We demonstrate the technique
on several objects and facades
GelSlim: A High-Resolution, Compact, Robust, and Calibrated Tactile-sensing Finger
This work describes the development of a high-resolution tactile-sensing
finger for robot grasping. This finger, inspired by previous GelSight sensing
techniques, features an integration that is slimmer, more robust, and with more
homogeneous output than previous vision-based tactile sensors. To achieve a
compact integration, we redesign the optical path from illumination source to
camera by combining light guides and an arrangement of mirror reflections. We
parameterize the optical path with geometric design variables and describe the
tradeoffs between the finger thickness, the depth of field of the camera, and
the size of the tactile sensing area. The sensor sustains the wear from
continuous use -- and abuse -- in grasping tasks by combining tougher materials
for the compliant soft gel, a textured fabric skin, a structurally rigid body,
and a calibration process that maintains homogeneous illumination and contrast
of the tactile images during use. Finally, we evaluate the sensor's durability
along four metrics that track the signal quality during more than 3000 grasping
experiments.Comment: RA-L Pre-print. 8 page
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