论文标题

HyperFlow:将3D对象表示为表面

HyperFlow: Representing 3D Objects as Surfaces

论文作者

Spurek, Przemysław, Zięba, Maciej, Tabor, Jacek, Trzciński, Tomasz

论文摘要

在这项工作中,我们提出了HyperFlow - 一种新颖的生成模型,该模型利用HyperNetworks直接以轻质表面(网格)形式创建连续的3D对象表示形式,直接在点云之外。有效的对象表示对于许多计算机视觉应用至关重要,包括机器人操纵和自动驾驶。但是,创建这些表示通常很麻烦,因为它需要处理无序的点云集。因此,由于诸如排列不变性之类的其他优化约束,它在计算上昂贵,或者导致Binning Point Clouds引入的量化损失陷入离散体素中。受计算机图形中使用的对象的基于网格的表示的启发,我们假定一种根本不同的方法,并表示3D对象作为表面家族。为此,我们设计了一个生成模型,该模型使用超网络来返回连续归一化流(CNF)目标网络的权重。该目标网络的目的是将概率分布的映射到3D网格。为了避免CNF在紧凑的支持分布上的数值不稳定,我们提出了一个新的球形对数正态函数,该函数模拟了对象表面周围3D点的密度,模仿了3D捕获设备引入的噪声。结果,我们获得了基于网格的对象表示,这些对象表示比竞争方法获得更好的定性结果,同时将训练时间减少到超过数量级。

In this work, we present HyperFlow - a novel generative model that leverages hypernetworks to create continuous 3D object representations in a form of lightweight surfaces (meshes), directly out of point clouds. Efficient object representations are essential for many computer vision applications, including robotic manipulation and autonomous driving. However, creating those representations is often cumbersome, because it requires processing unordered sets of point clouds. Therefore, it is either computationally expensive, due to additional optimization constraints such as permutation invariance, or leads to quantization losses introduced by binning point clouds into discrete voxels. Inspired by mesh-based representations of objects used in computer graphics, we postulate a fundamentally different approach and represent 3D objects as a family of surfaces. To that end, we devise a generative model that uses a hypernetwork to return the weights of a Continuous Normalizing Flows (CNF) target network. The goal of this target network is to map points from a probability distribution into a 3D mesh. To avoid numerical instability of the CNF on compact support distributions, we propose a new Spherical Log-Normal function which models density of 3D points around object surfaces mimicking noise introduced by 3D capturing devices. As a result, we obtain continuous mesh-based object representations that yield better qualitative results than competing approaches, while reducing training time by over an order of magnitude.

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