PM2 Quadtree Demo

Link(s)
http://donar.umiacs.umd.edu/quadtree/lines/pm2.html
Topic(s)
Line Representations, Spatial Search Structures



Recommendation
  
Lecture Aide Has Potential
Self-study Supplement Has Potential
Standalone Has Potential
Debugging Aide Has Potential
Works?
Yes
Delivery Method(s)
Java Applet
Project
Maryland Spatial Index Demos
Project Relationship
Part of project
Language(s)
English
Author(s)
Frantisek Brabec, Hanan Samet
Institution(s)
University of Maryland
Activity Level(s)
User data
Source Code License
Unavailable
First Published
N/A
Last Modified
N/A

Description
This tool can be used to visualize a number of different decompositions. The main visualization window is zoomable and the user can optionally overlay it with a grid. There are a number of operations that can be performed. Users can insert, move and delete lines that define the structure. In addition, the user can perform three test, near, within and overlap. For the tests, the user is given the option of what kind of shape to use for the test: point, rectangle, polygon, path, etc. The application of the tests is animated, with controls given for pausing the animation and controlling the speed. In addition, the animation can be made to stop at logical phase points (such as when an object is encountered.
Evaluation
This a full-feature visualization and has many of the attributes that we look for in a good visualization. It is “integrated” with the other spatial data structure visualizations available at this site. It clearly shows the decomposition process for the data structure. Unfortunately, there is very little feedback about what is going on. It would be a big help if there were some form of textual log that explains the steps taking place. Even some kind of description of the basic operations would be good. There is some discussion about what the operations do in theory on the higher level page containing this applet (http://donar.umiacs.umd.edu/quadtree/), but it is fairly minimal (they would still do well to have a link from the visualization back to this page, which they don’t at the moment). The interface is generally good, but has some confusing aspects. There are some options that popup new windows and others that change the algorithm and actually move to another page on the site. This might not be a problem except that there is no way to know that it is going to happen until the control is tried. The main target of this visualization seems to be self study, but with the lack of documentation or explanation, a secondary source of information is really needed to augment this.
Usage Notes
This is a Java applet, so clicking on the link above should start the AV. The main portion of the applet is a white box where you can click to add data points. As you add more points, the decomposition lines that build up the quadtree structure will appear. Various controls let you modify the behavior of the AV.
Field Report(s)
References
N/A
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AV of the Day
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Score
44