Fast Multi-View 3D reconstruction of seedlings based on automatic viewpoint planning

Abstract

Three-dimensional models of plants provide valuable phenotypic information. Phenotypic measurements of plant structures are essential for monitoring plant growth and understanding plant responses to environmental changes. Existing 3D reconstruction techniques have achieved accurate reconstruction models of some plants such as corn and soybeans. However, several drawbacks exist in current plant 3D reconstruction systems, including high cost, fixed capture perspectives and complex operation. To address these issues and considering the influence of camera capture angles on model reconstruction accuracy, we investigated a viewpoint planning reconstruction method. We designed a plant seedling reconstruction system that utilizes a consumer-grade L515 LiDAR sensor and a precision turntable. We establish a viewpoint rule based on the camera imaging model of the three-dimensional spatial structure of leaves, constructing minimum constraints on the leaf normal vector and the camera optical axis. This enables to determine the optimal capture viewpoint for each leaf to obtain the maximum leaf information. The angle β between the leaf normal vector and the camera optical axis serves as the basis for the turntable rotation, systematically planning the rotation of the turntable to enable the camera to capture the maximum useful leaf information. Unlike static camera-based turntable reconstruction systems that capture images at fixed angle intervals, we plan the rotation of the turntable based on the acquired information. This allows us to obtain more effective point cloud information of plant seedlings from the same or even fewer images, reducing the collection of redundant images and reconstructing more accurate plant seedling 3D models. Additionally, we measured commonly used leaf traits in plant phenotypic studies, such as leaf length, leaf width, and leaf area. The leaf area measured based on the reconstructed seedling model exhibited high accuracy (R2 > 0.99). The results of this study demonstrate that the consumer-grade L515 LiDAR sensor combined with the proposed viewpoint planning method can effectively reconstruct accurate seedling 3D models and measure phenotypic information. Due to the absence of error accumulation caused by adjacent view registration, this approach offers advantages such as shorter reconstruction time, higher efficiency and increased accuracy compared to some multi-view point cloud registration and reconstruction methods. Therefore, this system can be applied to three-dimensional reconstruction and phenotype analysis of plant seedlings due to its high efficiency and accuracy.