US 2003/0113011 A1 · Cast shadows and linear subspaces for object recognition

Abstract

The present invention is a method of deriving a reflectance function that analytically approximates the light reflected from an object model in terms of the spherical harmonic components of light. The reflectance function depends upon the intensity of light incident at each point on the model, but excludes light originating from below a local horizon, therefore not contributing to the reflectance because of the cast shadows. This reflectance function is used in the process of machine vision, by allowing a machine to optimize the reflectance function and arrive at an optimal rendered image of the object model, relative to an input image. Therefore, the recognition of an image produced under variable lighting conditions is more robust. The reflectance function of the present invention also has applicability in other fields, such as computer graphics.

Claims8

Dependent claims

A method of recognizing objects under various lighting conditions comprising the steps of:

(a) providing a database comprising a plurality of three dimensional models;
(b) providing an input image;
(c) positioning each three dimensional model relative to the input image;
(d) determining, for each three dimensional model, an optimal rendered image which is most similar to the input image, said determining step comprising:
(i) deriving a reflectance function that describes an approximation of the set of all possible rendered images that each three dimensional model can produce under all possible lighting conditions, wherein said reflectance function analytically excludes illumination within cast shadows on said model;
and
(ii) optimizing the reflectance function to determine an optimal rendered image of each model that is most similar to the input image;
(e) computing a measure of similarity between the input image and each optimal rendered image;
and
(f) selecting the three dimensional model corresponding to the optimal rendered image whose measure of similarity is most similar to the input image.

7 more elements

Dependencies are inferred from the claim text.

Cast shadows and linear subspaces for object recognition

Life of this patent

Cast shadows and linear subspaces for object recognition

Life of this patent

Abstract

Claims8