When playing tours authored in KML, is it possible to dynamically to control the camera?

Question

Using the Google Earth plugin AI, I want to play a tour authored in KML with the touring capability, but let the user modify the camera controls during the play.

Is it possible?

Answer 1

It depends on how much modification you want to allow.

Tour playback is designed to work with the user changing the orientation of the view (via dragging or the camera controls), but not the position. If the user stops changing the view for long enough, the camera will smoothly snap back to the default orientation for that point in the tour. The zoom and panning controls disappear during the tour, but if the user tries to change the camera position via other methods (like the keyboard), the tour will typically be paused.

The Earth API, however, allows you to absorb or change any of those event behaviors, since you can add a listener for mouse and keyboard events and prevent them from processing as usual or act on them in a completely different way.

If you haven't tried it, there's a tour example in the Google Code Playground where you can see what happens with different interactions based on the default event responses.

Finally, if you want really custom tour behavior -- like allowing certain kinds of movement of the camera away from the tour path even as the tour continues -- you will most likely need to write your own camera movement code. Getting the basics of this working isn't too difficult, but getting the right intuitive feel for that kind of interaction is difficult, and probably dataset-dependent. To get started, you can parse the KML directly, find the tour and the tour primitives it contains, and then use the regular camera controls you cited to move between those primitives, adding offsets for any user-supplied movements.

edit: the Earth API tour page cited in the question has an example of getting started with parsing the KML file by getting the plugin to do it for you. You can use this to implement the above suggestion by using the KML DOM walking code to find all the tour primitives (instead of halting as soon as a Tour element is found).

This isn't always the most efficient approach (plugin function calls have overhead, and meanwhile browsers have built-in XML parsing capabilities), but it may be the most straightforward way to start. For many tours, this approach would be perfectly sufficient.

Answer 2

It is possible, but pretty hard to implement and even harder to control well. I have been playing around with trying to do this for quite a while now. I have not had much success myself, but here are two example by others who have made some progress.

Firstly, the underlying principle they are using is based upon the TICK - a simple example of it is here http://earth-api-samples.googlecode.com/svn/trunk/examples/event-frameend.html

The two example are : http://maps.myosotissp.com/ and http://racemyrace.com/race.php

Also, here is an example that used to work up until recently, I am not sure why it has stopped but it appears you can still read the JS being used. It is made by the same person who created the racemyrace website http://www.thekmz.co.uk/GEPlugin/pathtour/v3/path_tour_v3.htm

If you happen to work something out, I would appreciate you creating a simple example page and sharing the link. It will probably take a while so if you could look up my email via profile and notify me that would be even better.

Good Luck!