CS 184: COMPUTER GRAPHICS

Lecture #29 -- Mon 5/11/2009.

Warm-up :

Image Stitching

Image-based Rendering

By analyzing the differences of their relative positions in the two images, one can extract 3D depth information.
Thus groups of pixels in both images can be annotated with a distance from the camera that took them.
This basic approach can be extended to many different pictures taken from many different camera locations.
The depth annotation establishes an implicit 3D database of the geometry of the model object or scene.

To produce a new image from a new camera location, one selects images taken from nearby locations
and suitably shifts or "shears" the pixel positions according to their depth and the difference in camera locations.
The information from the various nearby images is then combined in a weighted manner,
where closer camera positions, or the cameras that see the surface of interest under a steeper angle, are given more weight.
With additional clever processing, information missing in one image (e.g., because it is hidden behind a telephone pole)
can be obtained from another image taken from a different angle,
or can even be procedurally generated by extending nearby texture patterns.

Example 1: Stereo from a single source: A depth-annotated image of a 3D object, rendered from two different camera positions.
Example 2: Interpolating an image from neighboring positions:

To Learn More:  UNC Image-Based Rendering
Future Graduate Courses: 283, 294x ...
 

Light Field Rendering

As an approximation, one captures many renderings from many locations (often lying on a regular array of positions and directions),
ideally, all around the given model object, but sometimes just from one dominant side.
This information is then captured in a 4D sampled function (2D array of locations, with 2D sub arrays of directions).
One practical solution is to organize and index this information (about all possible light rays in all possible directions)
by defining the rays by their intercept coordinates (s,t) and (u,v) of two points lying on two parallel planes.
The technique is applicable to both synthetic and real worlds, i.e. objects they may be rendered or scanned.
Creating a light field from a set of images corresponds to inserting 2D slices into the 4D light field representation.
Once a light field has been created, new views may be constructed by extracting 2D slices in appropriate directions.

3D Data acquisition

Volume Rendering

Rapid Prototyping

My Own Use of Computer Graphics

Where to go from here ... ?

Undergraduate Courses:

Graduate Courses:

Specialty Graduate Courses (taught about avery 2-3 years):