What is light? Electromagnetic radiation (EMR) moving along rays in space R( ) is EMR, measured in...
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Transcript of What is light? Electromagnetic radiation (EMR) moving along rays in space R( ) is EMR, measured in...
![Page 1: What is light? Electromagnetic radiation (EMR) moving along rays in space R( ) is EMR, measured in units of power (watts) – is wavelength Light: Travels.](https://reader035.fdocuments.us/reader035/viewer/2022070402/56649f225503460f94c3aed9/html5/thumbnails/1.jpg)
What is light?Electromagnetic radiation (EMR) moving along rays in
space• R() is EMR, measured in units of power (watts)
– is wavelength
Light:• Travels far• Travels fast• Travels in straight lines• Interacts with stuff• Bounces off things• Is produced in nature• Has lots of energy
-- Steve Shafer
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Point of observation
Figures © Stephen E. Palmer, 2002
What do we see?
3D world 2D image
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Point of observation
What do we see?
3D world 2D image
Painted backdrop
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On Simulating the Visual ExperienceJust feed the eyes the right data
• No one will know the difference!
Philosophy:• Ancient question: “Does the world really exist?”
Science fiction:• Many, many, many books on the subject, e.g. slowglass from
“Light of Other Days”
• Latest take: The Matrix
Physics:• Slowglass might be possible?
Computer Science:• Virtual Reality
To simulate we need to know:
What does a person see?
![Page 5: What is light? Electromagnetic radiation (EMR) moving along rays in space R( ) is EMR, measured in units of power (watts) – is wavelength Light: Travels.](https://reader035.fdocuments.us/reader035/viewer/2022070402/56649f225503460f94c3aed9/html5/thumbnails/5.jpg)
The Plenoptic Function
Q: What is the set of all things that we can ever see?
A: The Plenoptic Function (Adelson & Bergen)
Let’s start with a stationary person and try to parameterize everything that he can see…
Figure by Leonard McMillan
![Page 6: What is light? Electromagnetic radiation (EMR) moving along rays in space R( ) is EMR, measured in units of power (watts) – is wavelength Light: Travels.](https://reader035.fdocuments.us/reader035/viewer/2022070402/56649f225503460f94c3aed9/html5/thumbnails/6.jpg)
Grayscale snapshot
is intensity of light • Seen from a single view point
• At a single time
• Averaged over the wavelengths of the visible spectrum
(can also do P(x,y), but spherical coordinate are nicer)
P()
![Page 7: What is light? Electromagnetic radiation (EMR) moving along rays in space R( ) is EMR, measured in units of power (watts) – is wavelength Light: Travels.](https://reader035.fdocuments.us/reader035/viewer/2022070402/56649f225503460f94c3aed9/html5/thumbnails/7.jpg)
Color snapshot
is intensity of light • Seen from a single view point
• At a single time
• As a function of wavelength
P()
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A movie
is intensity of light • Seen from a single view point
• Over time
• As a function of wavelength
P(,t)
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Holographic movie
is intensity of light • Seen from ANY viewpoint
• Over time
• As a function of wavelength
P(,t,VX,VY,VZ)
![Page 10: What is light? Electromagnetic radiation (EMR) moving along rays in space R( ) is EMR, measured in units of power (watts) – is wavelength Light: Travels.](https://reader035.fdocuments.us/reader035/viewer/2022070402/56649f225503460f94c3aed9/html5/thumbnails/10.jpg)
The Plenoptic Function
• Can reconstruct every possible view, at every moment, from every position, at every wavelength
• Contains every photograph, every movie, everything that anyone has ever seen! it completely captures our visual reality! Not bad for a function…
P(,t,VX,VY,VZ)
![Page 11: What is light? Electromagnetic radiation (EMR) moving along rays in space R( ) is EMR, measured in units of power (watts) – is wavelength Light: Travels.](https://reader035.fdocuments.us/reader035/viewer/2022070402/56649f225503460f94c3aed9/html5/thumbnails/11.jpg)
Sampling Plenoptic Function (top view)
Just lookup -- Quicktime VR
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2D: Image
What is an image?
All rays through a point• Panorama?
Slide by Rick Szeliski and Michael Cohen
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Image
Image plane
2D• position
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Spherical Panorama
All light rays through a point form a ponorama
Totally captured in a 2D array -- P()Where is the geometry???
See also: 2003 New Years Eve
http://www.panoramas.dk/fullscreen3/f1.html
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Environment Maps
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Capturing Real Illumination
From Flight of the Navigator
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Mirrored SphereMirrored Sphere
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Real-World Lighting Environments
Lighting Environments from the Light Probe Image Gallery:http://www.debevec.org/Probes/Lighting Environments from the Light Probe Image Gallery:http://www.debevec.org/Probes/
FunstonBeach
UffiziGallery
EucalyptusGrove
GraceCathedral
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CG Objects Illuminated by a Traditional CG Light Source
CG Objects Illuminated by a Traditional CG Light Source
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Paul Debevec. A Tutorial on Image-Based Lighting. IEEE Computer Graphics and Applications, Jan/Feb 2002.
Paul Debevec. A Tutorial on Image-Based Lighting. IEEE Computer Graphics and Applications, Jan/Feb 2002.
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What do we see?
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Shadows are the worst…
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Shadow transfer
++++ ====
Database image Shadow estimate Refined shadow
Object alone Shadow alone Object with shadow