334 research outputs found
Im2Pano3D: Extrapolating 360 Structure and Semantics Beyond the Field of View
We present Im2Pano3D, a convolutional neural network that generates a dense
prediction of 3D structure and a probability distribution of semantic labels
for a full 360 panoramic view of an indoor scene when given only a partial
observation (<= 50%) in the form of an RGB-D image. To make this possible,
Im2Pano3D leverages strong contextual priors learned from large-scale synthetic
and real-world indoor scenes. To ease the prediction of 3D structure, we
propose to parameterize 3D surfaces with their plane equations and train the
model to predict these parameters directly. To provide meaningful training
supervision, we use multiple loss functions that consider both pixel level
accuracy and global context consistency. Experiments demon- strate that
Im2Pano3D is able to predict the semantics and 3D structure of the unobserved
scene with more than 56% pixel accuracy and less than 0.52m average distance
error, which is significantly better than alternative approaches.Comment: Video summary: https://youtu.be/Au3GmktK-S
Evaluating 3D Shape Analysis Methods for Robustness to Rotation Invariance
This paper analyzes the robustness of recent 3D shape descriptors to SO(3)
rotations, something that is fundamental to shape modeling. Specifically, we
formulate the task of rotated 3D object instance detection. To do so, we
consider a database of 3D indoor scenes, where objects occur in different
orientations. We benchmark different methods for feature extraction and
classification in the context of this task. We systematically contrast
different choices in a variety of experimental settings investigating the
impact on the performance of different rotation distributions, different
degrees of partial observations on the object, and the different levels of
difficulty of negative pairs. Our study, on a synthetic dataset of 3D scenes
where objects instances occur in different orientations, reveals that deep
learning-based rotation invariant methods are effective for relatively easy
settings with easy-to-distinguish pairs. However, their performance decreases
significantly when the difference in rotations on the input pair is large, or
when the degree of observation of input objects is reduced, or the difficulty
level of input pair is increased. Finally, we connect feature encodings
designed for rotation-invariant methods to 3D geometry that enable them to
acquire the property of rotation invariance.Comment: 20th Conference on Robots and Vision (CRV) 202
The Repo homeodomain transcription factor suppresses hematopoiesis in Drosophila and preserves the glial fate
Despite their different origins, Drosophila glia and hemocytes are related cell populations that provide an immune function. Drosophila hemocytes patrol the body cavity and act as macrophages outside the nervous system whereas glia originate from the neuroepithelium and provide the scavenger population of the nervous system. Drosophila glia are hence the functional orthologs of vertebrate microglia, even though the latter are cells of immune origin that subsequently move into the brain during development. Interestingly, the Drosophila immune cells within (glia) and outside the nervous system (hemocytes) require the same transcription factor Glide/Gcm for their development. This raises the issue of how do glia specifically differentiate in the nervous system and hemocytes in the procephalic mesoderm. The Repo homeodomain transcription factor and pan-glial direct target of Glide/Gcm is known to ensure glial terminal differentiation. Here we show that Repo also takes center stage in the process that discriminates between glia and hemocytes. First, Repo expression is repressed in the hemocyte anlagen by mesoderm-specific factors. Second, Repo ectopic activation in the procephalic mesoderm is sufficient to repress the expression of hemocyte-specific genes. Third, the lack of Repo triggers the expression of hemocyte markers in glia. Thus, a complex network of tissue-specific cues biases the potential of Glide/Gcm. These data allow us to revise the concept of fate determinants and help us understand the bases of cell specification. Both sexes were analyzed.SIGNIFICANCE STATEMENTDistinct cell types often require the same pioneer transcription factor, raising the issue of how does one factor trigger different fates. In Drosophila, glia and hemocytes provide a scavenger activity within and outside the nervous system, respectively. While they both require the Glide/Gcm transcription factor, glia originate from the ectoderm, hemocytes from the mesoderm. Here we show that tissue-specific factors inhibit the gliogenic potential of Glide/Gcm in the mesoderm by repressing the expression of the homeodomain protein Repo, a major glial-specific target of Glide/Gcm. Repo expression in turn inhibits the expression of hemocyte-specific genes in the nervous system. These cell-specific networks secure the establishment of the glial fate only in the nervous system and allow cell diversification
Generalizing Single-View 3D Shape Retrieval to Occlusions and Unseen Objects
Single-view 3D shape retrieval is a challenging task that is increasingly
important with the growth of available 3D data. Prior work that has studied
this task has not focused on evaluating how realistic occlusions impact
performance, and how shape retrieval methods generalize to scenarios where
either the target 3D shape database contains unseen shapes, or the input image
contains unseen objects. In this paper, we systematically evaluate single-view
3D shape retrieval along three different axes: the presence of object
occlusions and truncations, generalization to unseen 3D shape data, and
generalization to unseen objects in the input images. We standardize two
existing datasets of real images and propose a dataset generation pipeline to
produce a synthetic dataset of scenes with multiple objects exhibiting
realistic occlusions. Our experiments show that training on occlusion-free data
as was commonly done in prior work leads to significant performance degradation
for inputs with occlusion. We find that that by first pretraining on our
synthetic dataset with occlusions and then finetuning on real data, we can
significantly outperform models from prior work and demonstrate robustness to
both unseen 3D shapes and unseen objects
MOPA: Modular Object Navigation with PointGoal Agents
We propose a simple but effective modular approach MOPA (Modular ObjectNav
with PointGoal agents) to systematically investigate the inherent modularity of
the object navigation task in Embodied AI. MOPA consists of four modules: (a)
an object detection module trained to identify objects from RGB images, (b) a
map building module to build a semantic map of the observed objects, (c) an
exploration module enabling the agent to explore the environment, and (d) a
navigation module to move to identified target objects. We show that we can
effectively reuse a pretrained PointGoal agent as the navigation model instead
of learning to navigate from scratch, thus saving time and compute. We also
compare various exploration strategies for MOPA and find that a simple uniform
strategy significantly outperforms more advanced exploration methods
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