VIP

VIP is a java applet that calculates the visibility polygon in linear time.

there might be a problem while loading or saving files. this might not work with actual browsers because they don't support the standard java 1.0 file dialogs. try the java appletviewer from sun. the applet needs your permission to read directory contents, to save or read a file.

Quick Help

input a polygon

press left mouse button to set polygon point.
when finished press right mouse button to connect the first and the last point.
the polygon should be simple. if it's not simple, you get a message and you have to draw the polygon again.

set the visibility point

simply click where you want to set the visibility point. you can also drag the point and see how the visibility polygon changes.
the visibility point should be inside the polygon. if the point is outside, it changes to blue.

editing the polygon

you can drag and drop polygon points. if you drag a point, such that the polygon wont be simple anymore, the mouse releases the point before that happens.

zooming

if you click on the zoom-button, you switch to zoom mode. if you want to leave the zoom mode, simply click again on that button.
in zoom mode you can draw rectangles to specify the area you want to zoom in. the aspect ratio will be maintained. click the right mouse button to see the previous adjustment.

loading and saving from/to local files

you can load and save scenes to your local drive simply by clicking on the open/save buttons. however, this does not work for the most browsers, because their java-implementation does not contain the class FileDialog. you can use the 'appletviewer' from sun instead.
in order to load and save work, the applet requires approval to read directory contents, to read / write files. the method to give the approval depends on the browser you use.

loading and saving over the network

this applet can download saved scenes via the internet using an url connection and the http protocol. clicking on the network load button will pop up a dialog to select a file for download. this might take a while depending on your connection.
uploading works in a similar way.

replay control

for every scene you can replay the calculation of the visibility polygon in detail. (step by step.)