SEGMENTATION OF COMPLEX STRUCTURES IN POINT CLOUDS USING DEEP NEURAL NETWORKS
Abstract
Background. Point cloud part segmentation assigns a semantic part label to every point and provides a more detailed description of object geometry than object-level classification. Architecture selection remains difficult because models with similar aggregate benchmark scores may differ substantially in category-level reliability and computational cost.
Materials and Methods. This study compares PointNet++, Dynamic Graph Convolutional Neural Network (DGCNN), and Point Transformer on the ShapeNet Part benchmark, which represents sixteen object categories with fifty part labels. Final evaluation was performed on 2,874 test shapes represented by 2,048 points. Segmentation quality was assessed using point accuracy, class-average accuracy, class mean intersection over union (mIoU), and instance mean intersection over union (mIoU). A separate batch-size-one benchmark measured inference latency, throughput, and graphics memory use.
Results and Discussion. Point Transformer achieved the highest overall quality, with 94.4% point accuracy, 87.7% class-average accuracy, 82.9% class mIoU, and 85.7% instance mIoU. DGCNN reached 85.3% instance mIoU while requiring only 15.87 ms per shape, compared with 53.39 ms for Point Transformer and 344.62 ms for PointNet++. Aggregate differences were small, but category-level results were more pronounced. Point Transformer produced the highest mIoU in eight of sixteen categories, while DGCNN and PointNet++ led in five and three categories, respectively. The largest architecture-dependent differences were observed for Motorbike, Earphone, and Rocket, demonstrating that similar overall scores can conceal distinct failure patterns.
Conclusion. No architecture dominated all practical criteria. Point Transformer provided the strongest segmentation quality, whereas DGCNN offered the most favorable measured speed-quality trade-off. PointNet++ remained competitive in quality but showed substantially higher latency in the evaluated implementation. Model selection should therefore consider category-level behavior, input configuration, and computational constraints together with aggregate mIoU.
Keywords: point cloud segmentation, part segmentation, ShapeNet Part, PointNet++, DGCNN, Point Transformer
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DOI: http://dx.doi.org/10.30970/eli.35.4
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