Shape and material recovery from object motion with application to relighting

1. A method for shape and material recovery from object motion of an object, comprising:

modeling using a processor dichromatic dependence of surface reflectance on surface normal, lighting and viewing directions to derive a differential flow relation from an image of the object;

determining a rank deficiency in a sequence of differential flow relations and use the rank deficiency to handle complex bidirectional reflectance distribution functions (BRDFs);

estimating BRDF-derivatives from the differential flow relations to recover the complex BRDF; and

reconstructing depth of the object without knowledge of their BRDFs for joint shape and material recovery; and

using the rank deficiency to recover depth and reflectance of the object.

2. The method of claim 1 , comprising applying recovered shape and reflectance functions to predict an appearance of the object under novel lighting and relight other objects with novel shapes under the novel lighting.

3. The method of claim 1 , comprising deriving a differential flow relation for dichromatic BRDFs and relating the flow relation to a surface depth.

4. The method of claim 1 , comprising determining a rank deficiency in the relation across different images.

5. The method of claim 1 , wherein the BRDF and light direction are unknown, comprising using four or more differential motions of the object to eliminate BRDF terms to recover surface depth.

6. The method of claim 1 , wherein the BRDF is unknown and composed of a sum of dichromatic lobes, comprising using four or more differential motions of the object to derive a linear system comprising an albedo and BRDF-derivatives.

7. The method of claim 6 , comprising using the linear system to recover the albedo and BRDF.

8. The method of claim 1 , given images of a moving object of unknown shape, with an unknown dichromatic BRDF, comprising estimating shape and reflectance for appearance prediction and relighting application.

9. The method of claim 1 , comprising determining a point on a BRDF-curve corresponding to reflectance of a surface point under predetermined lighting.

10. The method of claim 9 , comprising predicting an appearance of the object under predetermined lighting.

11. The method of claim 1 , for an object with predetermined geometry, observed under predetermined lighting, comprising determining a point on the BRDF-curve corresponding to the reflectance of each surface point.

12. The method of claim 11 , comprising relighting the object under predetermined lighting.

13. A system for shape and material recovery of an object from motion, comprising:

a processor;

a camera coupled to the processor;

computer code for modeling the correct dichromatic dependence of surface reflectance on surface normal, lighting and viewing directions to derive a differential flow relation from an image of the object;

computer code for determining a rank deficiency in a sequence of differential flow relations and use the rank deficiency to handle complex bidirectional reflectance distribution functions (BRDFs);

computer code for estimating BRDF-derivatives from the differential flow relations to recover the complex BRDF; and

computer code for reconstructing depth of the object that reflects light without the BRDFs for shape recovery and using the rank deficiency to recover depth and reflectance of the object.

14. The system of claim 13 , comprising computer code for applying recovered shape and reflectance functions to predict an appearance of the object under novel lighting and relight other objects with novel shapes under the novel lighting.

15. The system of claim 13 , comprising computer code for deriving a differential flow relation for dichromatic BRDFs and relating the flow relation to a surface depth.

16. The system of claim 13 , comprising computer code for determining a rank deficiency in the relation across different images.