Fig. 1. Angles schematic in BRDF measurement

Fig. 2. Activation effect of ReLU. (a) Before activation; (b) after activation

Fig. 3. Dropout diagram

Fig. 4. Modeling process of DNN

Fig. 5. Fitting effect of anode plate coated by gold film. (a) θi=2°; (b) θi=15°; (c) θi=60°; (d) θi=75°

Fig. 6. Loss function value decline curve of anode plate coated by gold film

Fig. 7. Fitting effect of epoxy paint. (a) θi=2°; (b) θi=30°; (c) θi=75°; (d) θi=80°

Fig. 8. Loss function value decline curve of epoxy paint

Fig. 9. Comparison of fitting effects of three models for epoxy paint. DNN model: (a) θi=5°, (b) θi=30°; five-parameter model: (c) θi=5°, (d) θi=30°; Phong model: (e) θi=5°, (f) θi=30°

Fig. 10. Comparison of fitting effects of three models for polyimide film. DNN model: (a) θi=5°, (b) θi=30°; five-parameter model: (c) θi=5°, (d) θi=30°; Phong model: (e) θi=5°, (f) θi=30°