1,825 research outputs found
Partial wave analysis of decays with arbitrary spins
In this paper, we propose a method to construct the decay amplitudes in the
orbital () and spin () coupling scheme for particles with arbitrary
spins. For the decay with only massive particles involved, the angular
dependence is completely encoded in the angular momentum part, and the spins of
daughter particles are coupled in the rest frame of the mother particle, which
contributes only a constant factor. For the sequential decay, the total
amplitude is constructed by the two amplitudes evaluated in the rest
frame of their own mother particles, and then they are transformed to the
common frame, usually chosen as the laboratory frame, by certain Lorentz
transformations. In this way, it is easy to add the amplitudes of possible
different decay chains coherently. If massless particles show up in the final
states, the polarizations are expressed in helicity basis and the amplitudes
are modified correspondingly.Comment: 12 pages, 0 figure
SDM-NET: Deep Generative Network for Structured Deformable Mesh
We introduce SDM-NET, a deep generative neural network which produces
structured deformable meshes. Specifically, the network is trained to generate
a spatial arrangement of closed, deformable mesh parts, which respect the
global part structure of a shape collection, e.g., chairs, airplanes, etc. Our
key observation is that while the overall structure of a 3D shape can be
complex, the shape can usually be decomposed into a set of parts, each
homeomorphic to a box, and the finer-scale geometry of the part can be
recovered by deforming the box. The architecture of SDM-NET is that of a
two-level variational autoencoder (VAE). At the part level, a PartVAE learns a
deformable model of part geometries. At the structural level, we train a
Structured Parts VAE (SP-VAE), which jointly learns the part structure of a
shape collection and the part geometries, ensuring a coherence between global
shape structure and surface details. Through extensive experiments and
comparisons with the state-of-the-art deep generative models of shapes, we
demonstrate the superiority of SDM-NET in generating meshes with visual
quality, flexible topology, and meaningful structures, which benefit shape
interpolation and other subsequently modeling tasks.Comment: Conditionally Accepted to Siggraph Asia 201
A Revisit of Shape Editing Techniques: from the Geometric to the Neural Viewpoint
3D shape editing is widely used in a range of applications such as movie
production, computer games and computer aided design. It is also a popular
research topic in computer graphics and computer vision. In past decades,
researchers have developed a series of editing methods to make the editing
process faster, more robust, and more reliable. Traditionally, the deformed
shape is determined by the optimal transformation and weights for an energy
term. With increasing availability of 3D shapes on the Internet, data-driven
methods were proposed to improve the editing results. More recently as the deep
neural networks became popular, many deep learning based editing methods have
been developed in this field, which is naturally data-driven. We mainly survey
recent research works from the geometric viewpoint to those emerging neural
deformation techniques and categorize them into organic shape editing methods
and man-made model editing methods. Both traditional methods and recent neural
network based methods are reviewed
TM-NET: Deep Generative Networks for Textured Meshes
We introduce TM-NET, a novel deep generative model for synthesizing textured
meshes in a part-aware manner. Once trained, the network can generate novel
textured meshes from scratch or predict textures for a given 3D mesh, without
image guidance. Plausible and diverse textures can be generated for the same
mesh part, while texture compatibility between parts in the same shape is
achieved via conditional generation. Specifically, our method produces texture
maps for individual shape parts, each as a deformable box, leading to a natural
UV map with minimal distortion. The network separately embeds part geometry
(via a PartVAE) and part texture (via a TextureVAE) into their respective
latent spaces, so as to facilitate learning texture probability distributions
conditioned on geometry. We introduce a conditional autoregressive model for
texture generation, which can be conditioned on both part geometry and textures
already generated for other parts to achieve texture compatibility. To produce
high-frequency texture details, our TextureVAE operates in a high-dimensional
latent space via dictionary-based vector quantization. We also exploit
transparencies in the texture as an effective means to model complex shape
structures including topological details. Extensive experiments demonstrate the
plausibility, quality, and diversity of the textures and geometries generated
by our network, while avoiding inconsistency issues that are common to novel
view synthesis methods
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