Introduction to Image-Based
Rendering
Lining Yang
[email protected]
A part of this set of slides reference slides used at
Standford by Prof. Pat Hanrahan and Philipp Slusallek.
11/18/2003
References:
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S. E. Chen, “QuickTime VR – An Image-Based Approach to
Virtual Environment Navigation,” Proc. SIGGRAPH ’95, pp. 2938, 1995
S. Gortler, R. Grzeszczuk, R. Szeliski, and M. Cohen, “The
Lumigraph,” Proc SIGGRAPH ’96, pp. 43-54, 1996
M. Levoy and P. Hanrahan, “Light Field Rendering,” Proc.
SIGGRAPH ’96, 1996.
L. McMillan and G. Bishop, “Plenoptic Modeling: An ImageBased Rendering System,” Proc. SIGGRAPH ’95, pp. 39-46, 1995
J. Shade, S. Gortler, Li-Wei He, and R. Szeliski, “Layered Depth
Images,” Proc. SIGGRAPH ’98, pp 231-242, 1998
Heung-Yeung Shum, Li-Wei He, “Rendering With Concentric
Mosaics,” Proc. SIGGRAPH ’99, pp. 299-306, 1999
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Problem Description
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Complex Rendering of Synthetic Scene
takes too long to finish
Interactivity is impossible
Interactive visualization of extremely
large scientific data is also not possible
Image-Based Rendering (IBR) is used
to accelerate the renderings.
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Examples of Complex
Rendering
Povray quaterly competition site March – June, 2001
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Examples of Large Dataset
LLNL ASCI Quantum molecular simulation site
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Image-Based Rendering (IBR)
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The models for conventional polygon-based
graphics have become too complex.
IBR represents complex 3D environments
using a set of images from different (predefined) viewpoints
It produces images for new views using these
finite initial images and additional
information, such as depth.
The computation complexity is bounded by
the image resolution, instead of the scene
complexity.
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Image-Based Rendering (IBR)
Mark Levoy’s 1997 Siggraph talk
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Overview of IBR Systems
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Plenoptic Function
QuicktimeVR
Light fields/lumigraph
Concentric Mosaics
Plenoptic Modeling and Layered Depth
Image
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Plenoptic Function
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Plenoptic function (7D) depicts light
rays passing through:
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center of camera at any location (x,y,z)
at any viewing angle ( , )
for every wavelength (  )
for any time ( t )
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Limiting Dimensions of
Plenoptic Functions
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Plenoptic modeling (5D) : ignore time &
wavelength
Lumigraph/Lightfield (4D) : constrain
the scene (or the camera view) to a
bounding box
2D Panorama : fix viewpoint, allow only
the viewing direction and camera zoom
to be changed
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Limiting Dimensions of
Plenoptic Functions
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Concentric mosaics (3D) : index all input
image rays in 3 parameters: radius, rotation
angle and vertical elevation
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Quicktime VR
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Using environmental
maps
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Cylindrical
Cubic
spherical
At a fixed point, sample
all the ray directions.
Users can look in both
horizontal and vertical
directions
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Mars Pathfinder Panorama
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Creating a Cylindrical
Panorama
From www.quicktimevr.apple.com
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Commercial Products
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QuickTime VR, LivePicture, IBM
(Panoramix)
VideoBrush
IPIX (PhotoBubbles), Be Here, etc.
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Panoramic Cameras
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Rotating Cameras
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Kodak Cirkut
Globuscope
Stationary Cameras
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Be Here
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Quicktime VR
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Advantages:
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Using environmental map
Easy and efficient
Disadvantages:
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Cannot move away from the current
viewpoint
No Motion Parallax
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Light Field and Lumigraph
• Take advantage of empty space to
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Reduce Plenoptic Function to 4D
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Object or viewpoint inside a convex hull
Radiance does not change along a line unless
blocked
Lightfield Parameterization
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Parameterize the radiance lines by the
intersections with two planes.
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A light Slab
t
L(u,v,s,t)
v
u
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s
Two Plane Parametrization
Focal plane (st)
Camera plane (uv)
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Object
Reconstruction
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(u, v) and (s, t) can be
calculated by
determining the
intersection of image
ray with the two planes
This can also be done
via texture mapping
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(x, y) to (u, v) or (s, t) is
a projective mapping
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Capturing Lightfields
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Need a 2D set of (2D) images
Choices:
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Camera motion: human vs. computer
Constraints on camera motion: planar vs.
spherical
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Easier to construct
Coverage and sampling uniformity
Light field gantry
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Applications:
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Designed by
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digitizing light
fields
measuring
BRDFs
range
scanning
Marc Levoy et
al.
Light Field
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Key Ideas:
4D function
- Valid outside convex
hull
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2D slice = image
- Insert to create
- Extract to display
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Lightfields
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Advantages:
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Simpler computation vs. traditional CG
Cost independent of scene complexity
Cost independent of material properties
and other optical effects
Disadvantages:
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Static geometry
Fixed lighting
High storage cost
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Concentric Mosaics
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Concentric mosaics : easy to capture,
small in storage size
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Concentric Mosaics
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A set of manifold mosaics constructed
from slit images taken by cameras
rotating on concentric circles
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Sample Images
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Rendering a Novel View
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Construction of Concentric
Mosaics
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Synthetic scenes
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uniform angular direction sampling
square root sampling in radial direction
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Construction of Concentric
Mosaics (2)
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Real scenes
Bulky, costly
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Cheaper, easier
Construction of Concentric
Mosaics (3)
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Problems with single camera:
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Limited horizontal fov
Non-uniform spatial horizontal resolution
Video sequence can be compressed
with VQ and entropy encoding (25X)
Compressed stream gives 20fps on
PII300
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Results
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Results (2)
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Image Warping
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McMillan’s 5D plenoptic modeling system
Render or capture reference views
Creating Novel Views
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Using reference views’ color and depth information
with the warping equation
For opaque scenes, the location or depth of the
point reflecting the color is usually determined.
Calculated using vision techniques for real
imagery.
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Image Warping (filling holes)
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Dis-occlusion problem: Previously occluded objects in
the reference view can be visible in the new view
Fill in holes from other viewpoints or images (Mark
William et al).
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Layered Depth Images
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Different primitives
according to depth
values
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Image
Image with depth
LDI
polygons
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Layered Depth Images
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Idea:
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Handle disocclusion
Store invisible geometry in depth images
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Layered Depth Image
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Data structure:
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Per pixel list of depth samples
Per depth sample:
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RGBA
Z
Encoded: Normal direction, distance
Layered Depth Images
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Computation:
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Implicit ordering
information
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Incremental warping
computation
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LDI is broken into four
regions according to
epipolar point
Start + xincr (back to
front order)
Splat size computation
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Table lookup
Layered Depth Images
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