# HOPC: Histogram of Oriented Principal Components of 3D Pointclouds for Action Recognition

arXiv: https://arxiv.org/abs/1408.3809 · HTML: https://mlsanity.com/paper/1408.3809/

## Key facts

- Cited by 15 papers in the map (data through 14 Oct 2026).
- First posted on arXiv 17 Aug 2014.

## Built on by (most cited first, 15 of 15)

- [Skeleton Cloud Colorization for Unsupervised 3D Action Representation Learning](https://mlsanity.com/paper/2108.01959/) (2021)
- [Temporal-Viewpoint Transportation Plan for Skeletal Few-shot Action Recognition](https://mlsanity.com/paper/2210.16820/) (2022)
- [Uncertainty-DTW for Time Series and Sequences](https://mlsanity.com/paper/2211.00005/) (2022)
- [3D Implicit Transporter for Temporally Consistent Keypoint Discovery](https://mlsanity.com/paper/2309.05098/) (2023)
- [Contrast-reconstruction Representation Learning for Self-supervised Skeleton-based Action Recognition](https://mlsanity.com/paper/2111.11051/) (2021)
- [Self-Supervised 3D Action Representation Learning with Skeleton Cloud Colorization](https://mlsanity.com/paper/2304.08799/) (2023)
- [3D Skeleton-based Few-shot Action Recognition with JEANIE is not so Na"ive](https://mlsanity.com/paper/2112.12668/) (2021)
- [SNAKE: Shape-aware Neural 3D Keypoint Field](https://mlsanity.com/paper/2206.01724/) (2022)
- [Analysis and Evaluation of Kinect-based Action Recognition Algorithms](https://mlsanity.com/paper/2112.08626/) (2021)
- [Focalized Contrastive View-invariant Learning for Self-supervised Skeleton-based Action Recognition](https://mlsanity.com/paper/2304.00858/) (2023)
- [Informative Sample Selection Model for Skeleton-based Action Recognition with Limited Training Samples](https://mlsanity.com/paper/2510.25345/) (2025)
- [FT-HID: A Large Scale RGB-D Dataset for First and Third Person Human Interaction Analysis](https://mlsanity.com/paper/2209.10155/) (2022)
- [When Spatial meets Temporal in Action Recognition](https://mlsanity.com/paper/2411.15284/) (2024)
- [Semantic Labeling of Human Action For Visually Impaired And Blind People Scene Interaction](https://mlsanity.com/paper/2201.04706/) (2022)
- [Lens Privacy Sealing: A New Benchmark and Method for Physical Privacy-Preserving Action Recognition](https://mlsanity.com/paper/2605.19578/) (2026)

## Abstract (arXiv)

Existing techniques for 3D action recognition are sensitive to viewpoint variations because they extract features from depth images which change significantly with viewpoint. In contrast, we directly process the pointclouds and propose a new technique for action recognition which is more robust to noise, action speed and viewpoint variations. Our technique consists of a novel descriptor and keypoint detection algorithm. The proposed descriptor is extracted at a point by encoding the Histogram of Oriented Principal Components (HOPC) within an adaptive spatio-temporal support volume around that point. Based on this descriptor, we present a novel method to detect Spatio-Temporal Key-Points (STKPs) in 3D pointcloud sequences. Experimental results show that the proposed descriptor and STKP detector outperform state-of-the-art algorithms on three benchmark human activity datasets. We also introduce a new multiview public dataset and show the robustness of our proposed method to viewpoint variations.