Image Processing 13. Shading Models Illumination Cone Aleix M. - PDF document

Image Processing 13. Shading Models Illumination Cone Aleix M. Martinez aleix@ece.osu.edu Illumination A 3D object illuminated with a light source. ^ n ^ s a Intensity at image point I(u,v) (u,v) T . I 1 x 2 I 2 I n x n x 1 • Consider an n -pixel image to be a point in an n -dimensional space, I Î R n . • Each pixel value is a coordinate of x . • This is the same we saw in stereo vision, when we compute point correspondences. We now want to find a representation that is invariant to the illumination. 1

Illumination Sphere Illumination Cone Illumination Cone x 2 x 1 2-light source Single light source images N-dimensional image lie on cone boundary x n Image Space 2

3D linear subspace a ( x,y ) f x (x,y) f y (x,y) albedo (surface normals) Original (Training) Images Surface. f(x,y) (albedo textured mapped on surface). [Georghiades, Belhumeur, Kriegman 01] Single Light Source Face Movie Eyes for Relighting From an image of an eye we can extract the information of the direction and type of ambient illumination. 3