Fig. 1. Experiment three steps and their corresponding positions

Fig. 2. Photon distribution map. (a) Photon distribution map based on Monte Carlo method; (b) photon distribution map based on diffusion model

Fig. 3. Flow chart of F-K offset algorithm

Fig. 4. Geometric diagram of BRDF

Fig. 5. Diffuse reflection and specular reflection

Fig. 6. Different types of BRDF curves

Fig. 7. Reconstruction results of typical types. (a) Result of type 1; (b) result of type 2; (c) result of type 3; (d) result of type 4

Fig. 8. BRDF curves for three instances

Fig. 9. Reconstruction results of instances. (a) Glass fiber; (b) purple red paint board; (c) cement board