LCE Kotisivu

S-114.204 Modelling of Perception


Home work assignment, second half

The second half of the home work consists of building a system that can infer the 3-dimensional structure of a wire frame model from 2-dimensional view, in a simple case. The scene S is a list of 3D positions of the nodes, and observation I is a list of the node position in the 2D image plane.


The following examples are from a matlab script, that contains base routines for the work. See download instructions below.

Example of 2D view Example of Maximum Likelihood fit of the 3D positions. The blue structure produces exactly the observed image. The view direction is from the upper right corner closer to the observer. There are infinite number of solutions S that give the observed image I.
Examples of Maximum a Posteriori (MAP) fits, with prior that favours large angles, and thus round objects. There are (at least) three local maxima in the posterior. The first two produce the well known Necker cube ambiquity, while the third is a bit less probable distorted solution.


Download instructions

Directory contains basic routines needed in the work. The zip-file contains all the files.

The demo script necker_demo.m contains ready to use code for computing the projection matrix from 3D to 2D (using orthographic or perspective projection), and to compute the angles of the structure. After unziping the zip-file, run the demo with command (in matlab version 5 or 6)
>> necker_demo


Short report must be delivered, containing explanation of the used methods, chosen priors, description of the test results and conclusions.

Also a matlab script that produces the requested results should be delivered. If some minimization tends to take long time (more than some seconds), the code can load a precomputed result, but the original computation code must be available (eg. in comments).

The report and matlab-codes can be delivered either by

Deadline: 31.5.2005

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Last updated 29.4.2005