Fig. 1. Pixel gray value of 3×3 window

Fig. 2. Neighborhood of circular symmetry. (a) (1,8); (b) (1.5,12); (c) (2,16)

Fig. 3. Processing results of the two modes. (a) Gray image; (b) original LBP operator; (c) improved LBP operator

Fig. 4. Neighborhood of pixel point

Fig. 5. Adjacent pixel

Fig. 6. Edges extracted by different thresholds. (a) Depth image; (b) automatic threshold; (c) threshold range is [0.32,0.8]; (d) threshold range is [0.08,0.2]

Fig. 7. Specific steps of the ScSPM model

Fig. 8. Flow chart of our algorithm

Fig. 9. Recognition results of the CAD-60 dataset

Fig. 10. Recognition results of the MSR Action Pairs dataset

Fig. 11. Recognition results of the SBU Kinect interaction dataset