SA-Det3D: Self-Attention Based Context-Aware 3D Object Detection

By Prarthana Bhattacharyya, Chengjie Huang and Krzysztof Czarnecki.

We provide code support and configuration files to reproduce the results in the paper: SA-Det3D: Self-Attention Based Context-Aware 3D Object Detection.
Our code is based on OpenPCDet, which is a clean open-sourced project for benchmarking 3D object detection methods.

Overview

Fig.1. Self-Attention augmented global-context aware backbone networks.

In this paper, we explore variations of self-attention for contextual modeling in 3D object detection by augmenting convolutional features with self-attention features.
We first incorporate the pairwise self-attention mechanism into the current state-of-the-art BEV, voxel, point and point-voxel based detectors and show consistent improvement over strong baseline models while simultaneously significantly reducing their parameter footprint and computational cost. We call this variant full self-attention (FSA).
We also propose a self-attention variant that samples a subset of the most representative features by learning deformations over randomly sampled locations. This not only allows us to scale explicit global contextual modeling to larger point-clouds, but also leads to more discriminative and informative feature descriptors. We call this variant deformable self-attention (DSA).

Results

• Self-attention (SA) systematically improves 3D object detection across state-of-the-art 3D detectors: PointPillars, SECOND and Point-RCNN. In this figure, we show 3D AP on moderate Car class of KITTI val split (R40) vs. the number of parameters (Top) and GFLOPs (Bottom) for baseline models and proposed baseline extensions with Deformable SA (DSA) and Full SA (FSA).

Fig.2. 3D Car AP with respect to params and FLOPs of baseline and proposed self-attention variants.

• We also illustrate qualitative performance on KITTI val split. We show that our method identifies missed detections and removes false positives. Red bounding box represents ground truth and green represents detector outputs. From left to right: (a) RGB image of challenging scenes. (b) Result of the state-of-the-art methods: PointPillars, SECOND, Point-RCNN and PV-RCNN. (c) Result of our full self-attention (FSA) augmented baselines, which uses significantly fewer parameters and FLOPs.

Fig.3. Visualizing qualitative results between baseline and our proposed self-attention module.

Model Zoo

We provide our proposed detection models in this section. The 3D AP results (R-40) on KITTI 3D Object Detection validation of the Car moderate category are shown in the table below.

Notes:

• For inference, our models have been tested with 1 Tesla V-100 GPU and Pytorch 1.3.
• We use the checkpoints released by OpenPCDet as our baseline for evaluation.
• Our models are trained with 4 Tesla V-100 GPUs and Pytorch 1.3.

	Car 3D AP	Params (M)	G-FLOPs	download
PointPillar_baseline	78.39	4.8	63.4	PointPillar
PointPillar_red	78.07	1.5	31.5	PointPillar-red
PointPillar_DSA	78.94	1.1	32.4	PointPillar-DSA
PointPillar_FSA	79.04	1.0	31.7	PointPillar-FSA
SECOND_baseline	81.61	4.6	76.7	SECOND
SECOND_red	81.11	2.5	51.2	SECOND-red
SECOND_DSA	82.03	2.2	52.6	SECOND-DSA
SECOND_FSA	81.86	2.2	51.9	SECOND-FSA
Point-RCNN_baseline	80.52	4.0	27.4	Point-RCNN
Point-RCNN_red	80.40	2.2	24	Point-RCNN-red
Point-RCNN_DSA	81.80	2.3	19.3	Point-RCNN-DSA
Point-RCNN_FSA	82.10	2.5	19.8	Point-RCNN-FSA
PV-RCNN_baseline	84.83	12	89	PV-RCNN
PV-RCNN_DSA	84.71	10	64	PV-RCNN-DSA
PV-RCNN_FSA	84.95	10	64.3	PV-RCNN-FSA

Usage

a. Clone the repo:

git clone --recursive https://github.com/AutoVision-cloud/SA-Det3D

b. Copy SA-Det3D src into OpenPCDet:

sh ./init.sh

c. Install OpenPCDet and prepare KITTI data:

Please refer to INSTALL.md for installation and dataset preparation.

d. Run experiments with a specific configuration file:

Please refer to GETTING_STARTED.md to learn more about how to train and run inference on this detector.

Citation

If you find this project useful in your research, please consider citing:

@misc{bhattacharyya2021sadet3d,
      title={SA-Det3D: Self-Attention Based Context-Aware 3D Object Detection}, 
      author={Prarthana Bhattacharyya and Chengjie Huang and Krzysztof Czarnecki},
      year={2021},
      eprint={2101.02672},
      archivePrefix={arXiv},
      primaryClass={cs.CV}
}

Acknowledgement

• second.pytorch
• PointRCNN
• PV-RCNN
• MLCVNet