Announcements
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Project 2 artifact winners |
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Project 3 |
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demo session at the end of
class |
Photometric Stereo
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Readings |
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Forsyth and Ponce, section 5.4 |
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online: http://www.cs.berkeley.edu/~daf/bookpages/pdf/chap05-final.pdf |
Diffuse reflection
Shape from shading
Photometric stereo
Solving the equations
More than three lights
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Get better results by using
more lights |
Computing light source
directions
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Trick: place a chrome sphere in the scene |
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the location of the highlight
tells you where the light source is |
Recall the rule for
specular reflection
Computing the light
source direction
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Can compute q (and hence N) from this figure |
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Now just reflect V about N to
obtain L |
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Depth from normals
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Get a similar equation for V2 |
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Each normal gives us two linear
constraints on z |
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compute z values by solving a
matrix equation |
Results…
Results…
Limitations
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Big problems |
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doesn’t work for shiny things,
semi-translucent things |
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shadows, inter-reflections |
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Smaller problems |
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camera and lights have to be
distant |
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calibration requirements |
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measure light source
directions, intensities |
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camera response function |
Trick for handling
shadows
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Weight each equation by the
pixel brightness: |