Displaying a huge number of polylines

[BrunoSpy]

Thank you for your ideas, I added a precision parameter depending on the number of displayed polylines and found a good compromise between performance and precision.

If you have other ideas, don't hesitate, I'm sure I can optimize more

For your interest : one day of traffic from/to Paris :

[nlneilson]

Looks good.

[what_nick]

Display lists would be basically breaking the design of worldwind code and writing your own "huge polylinelist" renderer. All the vertex data, colour data etc. is pushed into GL at once and stored there, as you pan around the verices are transformed. Since worldwind is having a general switch to VBO's this may not be necessary.

Cheers,

what_nick.

[tag]

Before we offer any advice, would you please describe how you are defining those lines in WW.

1. Is it one polyline per flight path, or one per flight-path segment?
2. Approximately how many points are in each flight path?
3. Are the flight-path position altitudes relative to the terrain or MSL? (Which altitude mode is appropriate?)
4. How many paths do you need to display simultaneously?
5. How often are the paths updated?

If you could post -- or if necessary, send me privately -- KML, shapefile or some other format we can read or quickly write a reader for, that would be maximally helpful. If that's not possible, then any information you can provide that allows us to synthesize a similar use case would be helpful.

[BrunoSpy]

1. One polyline per flight
2. One point every 3s approximately, but I managed to drop unnecessary points : each polyline has about 200-300 points
3. AMSL
4. about 2000
5. never, it's offline datas

You can grab my code here http://videso3d.googlecode.com
The relevant file is http://code.google.com/p/videso3d/so...acksLayer.java

I can send you my files by email if it takes attachments of 10Mo

[what_nick]

For this case I would suggest using Dropbox - it is pretty nifty. Attachments in email are a mess.

Cheers,

what_nick.

[baellwe]

Originally Posted by what_nick

Since worldwind is having a general switch to VBO's this may not be necessary.

Can you provide more information regarding this? Which classes and when can we begin to experiment with this sort implementation?

[tag]

In the 2/1/2011 release there is an app in the WW perfomance package named VeryManyPaths that draws 2000 paths of 300 positions each. Please run that in your environment. On an old iMac I get close to 20 FPS.

Also in this release is an updated version of Path that uses vertex buffer objects. They have to be explicitly enabled, but VeryManyPaths enables them. Without VBOs the frame rate is slightly lower, but the degree to which it's lower depends greatly on the hardware.

[BrunoSpy]

Thanks. Just waiting for the 2.1.11 build

[BrunoSpy]

I activated VBO, but I can't see a difference, except few glitches (vertical exaggeration is not applied directly, you must redraw all the objects ...)

By the way, I now use Path instead of Polyline, and it seems to be much more reactive, without activating VBO.