409 research outputs found
Spherical Transformer: Adapting Spherical Signal to CNNs
Convolutional neural networks (CNNs) have been widely used in various vision
tasks, e.g. image classification, semantic segmentation, etc. Unfortunately,
standard 2D CNNs are not well suited for spherical signals such as panorama
images or spherical projections, as the sphere is an unstructured grid. In this
paper, we present Spherical Transformer which can transform spherical signals
into vectors that can be directly processed by standard CNNs such that many
well-designed CNNs architectures can be reused across tasks and datasets by
pretraining. To this end, the proposed method first uses locally structured
sampling methods such as HEALPix to construct a transformer grid by using the
information of spherical points and its adjacent points, and then transforms
the spherical signals to the vectors through the grid. By building the
Spherical Transformer module, we can use multiple CNN architectures directly.
We evaluate our approach on the tasks of spherical MNIST recognition, 3D object
classification and omnidirectional image semantic segmentation. For 3D object
classification, we further propose a rendering-based projection method to
improve the performance and a rotational-equivariant model to improve the
anti-rotation ability. Experimental results on three tasks show that our
approach achieves superior performance over state-of-the-art methods
3D objects and scenes classification, recognition, segmentation, and reconstruction using 3D point cloud data: A review
Three-dimensional (3D) point cloud analysis has become one of the attractive
subjects in realistic imaging and machine visions due to its simplicity,
flexibility and powerful capacity of visualization. Actually, the
representation of scenes and buildings using 3D shapes and formats leveraged
many applications among which automatic driving, scenes and objects
reconstruction, etc. Nevertheless, working with this emerging type of data has
been a challenging task for objects representation, scenes recognition,
segmentation, and reconstruction. In this regard, a significant effort has
recently been devoted to developing novel strategies, using different
techniques such as deep learning models. To that end, we present in this paper
a comprehensive review of existing tasks on 3D point cloud: a well-defined
taxonomy of existing techniques is performed based on the nature of the adopted
algorithms, application scenarios, and main objectives. Various tasks performed
on 3D point could data are investigated, including objects and scenes
detection, recognition, segmentation and reconstruction. In addition, we
introduce a list of used datasets, we discuss respective evaluation metrics and
we compare the performance of existing solutions to better inform the
state-of-the-art and identify their limitations and strengths. Lastly, we
elaborate on current challenges facing the subject of technology and future
trends attracting considerable interest, which could be a starting point for
upcoming research studie
Potential applications of deep learning in automatic rock joint trace mapping in a rock mass
In blasted rock slopes and underground openings, rock joints are visible in different forms. Rock joints are often exposed as planes confining rock blocks and visible as traces on a well-blasted, smooth rock mass surface. A realistic rock joint model should include both visual forms of joints in a rock mass: i.e., both joint traces and joint planes. Imaged-based 2D semantic segmentation using deep learning via the Convolutional Neural Network (CNN) has shown promising results in extracting joint traces in a rock mass. In 3D analysis, research studies using deep learning have demonstrated outperforming results in automatically extracting joint planes from an unstructured 3D point cloud compared to state-of-the-art methods. We discuss a pilot study using 3D true colour point cloud and their source and derived 2D images in this paper. In the study, we aim to implement and compare various CNN-based networks found in the literature for automatic extraction of joint traces from laser scanning and photogrammetry data. Extracted joint traces can then be clustered and connected to potential joint planes as joint objects in a discrete joint model. This can contribute to a more accurate estimation of rock joint persistence. The goal of the study is to compare the efficiency and accuracy between using 2D images and 3D point cloud as input data. Data are collected from two infrastructure projects with blasted rock slopes and tunnels in Norway.Potential applications of deep learning in automatic rock joint trace mapping in a rock masspublishedVersio
Rotation Invariant Convolutions for 3D Point Clouds Deep Learning
Recent progresses in 3D deep learning has shown that it is possible to design
special convolution operators to consume point cloud data. However, a typical
drawback is that rotation invariance is often not guaranteed, resulting in
networks being trained with data augmented with rotations. In this paper, we
introduce a novel convolution operator for point clouds that achieves rotation
invariance. Our core idea is to use low-level rotation invariant geometric
features such as distances and angles to design a convolution operator for
point cloud learning. The well-known point ordering problem is also addressed
by a binning approach seamlessly built into the convolution. This convolution
operator then serves as the basic building block of a neural network that is
robust to point clouds under 6DoF transformations such as translation and
rotation. Our experiment shows that our method performs with high accuracy in
common scene understanding tasks such as object classification and
segmentation. Compared to previous works, most importantly, our method is able
to generalize and achieve consistent results across different scenarios in
which training and testing can contain arbitrary rotations.Comment: International Conference on 3D Vision (3DV) 201
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