lec20_light

lec20_light - Lecture 20 Light color and reflectance CS6670...

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Unformatted text preview: Lecture 20: Light, color, and reflectance CS6670: Computer Vision Noah Snavely Announcements • Final projects – Everyone should have received feedback by now – Midterm reports due November 24 – Final presentations tentatively scheduled for the final exam period: Wed, December 16, 7:00 PM - 9:30 PM Measuring height R H v z r b t R H Z Z t v b r r v b t image cross ratio H b t v v x v y Measuring height v z r b t v x v y vanishing line (horizon) v t m What if the point on the ground plane b 0 is not known? • Here the guy is standing on the box, height of box is known • Use one side of the box to help find b 0 as shown above b t 1 b 1 Camera calibration Goal: estimate the camera parameters • Version 1: solve for projection matrix ΠX x 1 * * * * * * * * * * * * Z Y X w wy wx • Version 2: solve for camera parameters separately – intrinsics (focal length, principle point, pixel size) – extrinsics (rotation angles, translation) – radial distortion Vanishing points and projection matrix * * * * * * * * * * * * Π 4 3 2 1 π π π π 1 π 2 π 3 π 4 π T 1 1 Π π = v x (X vanishing point) Z 3 Y 2 , similarly , v π v π origin world of projection 1 4 T Π π o v v v Π Z Y X Not So Fast! We only know v ’s up to a scale factor o v v v Π Z Y X c b a • Can fully specify by providing 3 reference points Calibration using a reference object...
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This note was uploaded on 09/27/2010 for the course CS 667 at Cornell.

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lec20_light - Lecture 20 Light color and reflectance CS6670...

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