# CAD Priors for Accurate and Flexible Instance Reconstruction

## TL;DR

This paper introduces a novel pipeline that leverages CAD priors for automatic, accurate, and flexible 3D instance reconstruction from unorganized point clouds, even in dynamic cluttered environments.

## Contribution

It proposes a fully automated method combining CAD priors, object detection, and pose graph optimization for high-fidelity 3D reconstruction in complex scenes.

## Key findings

- Effective reconstruction of objects up to 125m^3
- Automatic detection and segmentation in cluttered scenes
- High accuracy close to sensor noise levels

## Abstract

We present an efficient and automatic approach for accurate reconstruction of instances of big 3D objects from multiple, unorganized and unstructured point clouds, in presence of dynamic clutter and occlusions. In contrast to conventional scanning, where the background is assumed to be rather static, we aim at handling dynamic clutter where background drastically changes during the object scanning. Currently, it is tedious to solve this with available methods unless the object of interest is first segmented out from the rest of the scene. We address the problem by assuming the availability of a prior CAD model, roughly resembling the object to be reconstructed. This assumption almost always holds in applications such as industrial inspection or reverse engineering. With aid of this prior acting as a proxy, we propose a fully enhanced pipeline, capable of automatically detecting and segmenting the object of interest from scenes and creating a pose graph, online, with linear complexity. This allows initial scan alignment to the CAD model space, which is then refined without the CAD constraint to fully recover a high fidelity 3D reconstruction, accurate up to the sensor noise level. We also contribute a novel object detection method, local implicit shape models (LISM) and give a fast verification scheme. We evaluate our method on multiple datasets, demonstrating the ability to accurately reconstruct objects from small sizes up to $125m^3$.