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

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image processing 13 shading models illumination cone
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Image Processing 13. Shading Models Illumination Cone Aleix M. - - PDF document

Jan 14, 2024 199 likes •248 views

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

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1 Image Processing

  • 13. Shading Models

Illumination Cone

Aleix M. Martinez aleix@ece.osu.edu

Illumination

^ n ^ s a

I(u,v) A 3D object illuminated with a light source. Intensity at image point (u,v)T.

  • Consider an n-pixel image to be a point in an n-dimensional

space, I Î Rn.

  • 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.

x1 x2 xn I n I 2

I1

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2 Illumination Sphere Illumination Cone

N-dimensional Image Space

Single light source images lie on cone boundary 2-light source image

x1 x2 xn

Illumination Cone

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3

Original (Training) Images a(x,y) fx(x,y) fy(x,y) albedo (surface normals)

  • Surface. f(x,y)

(albedo textured mapped on surface). 3D linear subspace [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.