  3D visual perception tasks based on multi-camera images are essential for
autonomous driving systems. Latest work in this field performs 3D object
detection by leveraging multi-view images as an input and iteratively enhancing
object queries (object proposals) by cross-attending multi-view features.
However, individual backbone features are not updated with multi-view features
and it stays as a mere collection of the output of the single-image backbone
network. Therefore we propose 3M3D: A Multi-view, Multi-path,
Multi-representation for 3D Object Detection where we update both multi-view
features and query features to enhance the representation of the scene in both
fine panoramic view and coarse global view. Firstly, we update multi-view
features by multi-view axis self-attention. It will incorporate panoramic
information in the multi-view features and enhance understanding of the global
scene. Secondly, we update multi-view features by self-attention of the ROI
(Region of Interest) windows which encodes local finer details in the features.
It will help exchange the information not only along the multi-view axis but
also along the other spatial dimension. Lastly, we leverage the fact of
multi-representation of queries in different domains to further boost the
performance. Here we use sparse floating queries along with dense BEV (Bird's
Eye View) queries, which are later post-processed to filter duplicate
detections. Moreover, we show performance improvements on nuScenes benchmark
dataset on top of our baselines.
