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CAP 6415 COMPUTER VISION (Spring 1997)
Programming Assignment 1 (Due on Feb 11, 1997)

In this assignment you will be experimenting with photometric stereo. As we saw in class, photometric stereo tries to infer the surface orientations in a scene by considering 2D images created by a light source at different positions. You will write code to infer the scene surface orientations and submit an analysis in a report form.

A database of images is provided on babbage in the directory
( /home/cs/faculty/sarkar/vision/photometric). The images are in groups of three corresponding to the three positions of the light source. In the database there are also images which violate some of the assumptions of photometric stereo such as a point source "faraway". All images are in PGM format. See the README file in the directory to decipher the images.

You may code in any language of your choice. I would suggest that you consider MATLAB or the Motif based code used in your image processing class (look into /home/cs/faculty/goldgof/Motif) as your building block. The Motif based code will allow you to display images, to interact with them, and to add your own procedures. A document about the Motif code is available at Procopy (maybe filed under Digital Image Processing or Dr. Goldgof).

As a part of this assignment you have to

  1. Write code for photometric stereo.
    • Given three images and the orientation of the three corresponding light sources, you should be able to compute the surface orientation at each pixel. (You might consider using the quiver function in Matlab to see projections of the surface orientations.)

    • Scale the surface orientation vector so that it is of the form . Quantize the space and let the computed surface orientations vote in this space. Display this voted space as an image. Thus, if there are three planar surfaces in the scene, then you should should be able to see three "spots" in the voted space corresponding to the three surface orientation.
  2. Write a report of at most 10 pages describing your experiments with the image set. Your report should be written professionally in a word processor. The discussion should be broken up into sections and all tables and figures should be discussed. In your writeup investigate the performance of the photometric stereo algorithm under various conditions.

You need to submit a written report and a hard copy of the code you have written. And you have to demonstrate your code with Mat Clarke. The written report is due at 11 am on Feb 11, 1997. The demonstrations have to be done during Mat Clarke's office hours (11:30 am to 1 pm) on Feb 11 and Feb 12, 1997.

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Sudeep Sarkar
Wed Feb 12 17:35:25 EST 1997