Rendering with Concentric Rendering with Concentric MosaicsMosaics

Heung – Yeung ShumHeung – Yeung Shum

and and

Li – Wei HeLi – Wei He

Presentation By:

Jonathan A. Bockelman

AgendaAgenda

1) A general description of concentric mosaics

2) Rendering concentric mosaics

3) Capturing concentric mosaics

4) Some examples

5) Issues that still need to be resolved and future plans

6) A brief demo

Rendering Made Easy... Sort ofRendering Made Easy... Sort of

Boo!

Yay!

Problems with traditional

rendering schemes

The appeal of image-based

modeling and rendering

The plenoptic function

History of Plenoptic FunctionsHistory of Plenoptic Functions

What is a Concentric Mosaic?What is a Concentric Mosaic?

“A manifold mosaic”

A 3D plenoptic: radius, rotation angle, and vertical

elevation

A 3D image built from a series of 360° slit images

Rendering a Novel ViewRendering a Novel View

Any point within the outermost

circle can be the viewpoint

Rays tangent to the camera

paths are used

Bilinear interpolation between

neighboring mosaics can also

be used

The Problem of Non-Planar RaysThe Problem of Non-Planar Rays

Rays off the plane need to

be approximated

Objects assumed to have an

infinite depth

Vertical distortion is created

The Need for Depth CorrectionThe Need for Depth Correction

Depth correction can fix the

vertical distortion

3 types of depth correction

exist

Full Perspective CorrectionFull Perspective Correction

Individual corrections are made for each pixel

Exact depths of objects are necessary

Hole-filling problems are a complication

Excellent results are seen in synthetic scenes

Weak Perspective CorrectionWeak Perspective Correction

Corrections are made for each vertical line

Estimated depths are calculated

Vertical distortions can occur

Constant Depth ApproximationConstant Depth Approximation

A constant depth is used

Users can control the assumed depth

Vertical distortions are produced if the wrong

depth is given

Consequences of a 3D functionConsequences of a 3D function

Vertical parallax is not

captured

Much smaller data sets are

required

Users can move in a circular

region

Synthetic MosaicsSynthetic Mosaics

3D Studio Max can be used

Images are cut into slits

Depth values for each pixel can be found

Sampling is a bit tricky

How NOT to Do Real World ScenesHow NOT to Do Real World Scenes

A series of single-slit cameras on a rotating beam

A single camera that can slide along a beam

The Lone CameraThe Lone Camera

A single off-centered camera sits on a rotary table

Regular images are taken

Multiple concentric mosaics can be recreated

from one image

Ideal SolutionIdeal Solution

A single camera can

produce distortion

A few tangential cameras

along a beam can correct

the problem

How the Pros Do ItHow the Pros Do It

An single ordinary digital video camera is

used with a rotary table

The camera faces radially outward

1351 frames are captured in 90 seconds

The system is incredibly simple and efficient

The Lobby SceneThe Lobby Scene

3 concentric mosaics from a lobby scene

OcclusionOcclusion

Occlusion is captured.

Horizontal ParallaxHorizontal Parallax

Horizontal parallax is simulated quite well.

Lighting and GlareLighting and Glare

Spectacular lighting effects are easy to create.

Constant Depth Correction RevisitedConstant Depth Correction Revisited

Aspect ratios are maintained at the chosen depth

Objects at other depths are distorted

Point vs. Bilinear SamplingPoint vs. Bilinear Sampling

Point sampling is twice as

fast, but image quality is

lower

Bilinear sampling is slower,

but images are much

smoother

CompressionCompression

Since adjacent frames are very similar, a

majority of the data can be compressed.

Vector quantization and entropy coding allow

the 415Mb original video to be shrunk to 16Mb.

MPEG4 compression can reduce the data size

to 640k, but blocky artifacts are created.

Why Use Concentric Mosaics?Why Use Concentric Mosaics?Quick and easy image capture

Parallax and specular highlights are preserved

Much smaller data sets than Lumigraphs

No messy geometry and lighting

User interaction is automatically incorporated

Future EndeavorsFuture Endeavors

Correcting vertical distortion

Increasing the region of motion

Improving compression ratios

One Last ExampleOne Last Example

DemoDemo

Mathematical MadnessMathematical Madness