In order to integrate a virtual object in a real scene seamlessly in augmented reality(AR）system

we need to simulate the interactions of the virtual object with the illumination of the scene.Acquiring the knowledge of illuminant direction is crucial in this work.We present a novel approach for estimating the direction from a single image of a scene that is illuminated by a light source regardless it is point light source or directional one.We propose to employ a maker cube

which is used to register to determine the rigid transformation relating 2D images to known 3D geometry

and a lambertian probe sphere

which is used to estimate the light source direction by image processing.The key process is to find and extract the intensity occluding curve on the sphere.Experimental results show that our approach is computationally efficient and the light source direction can be accurately obtained by it.