3D rendering problems (holes)

[anaxa_gore]

Hi,

I am using the BIL/DDS module for geoserver to produce bil files for my WWJ client. The client is getting the good elevations information, but i get a really bad rendering. As said in the title, there are a lot of holes in the map. I join a screenshot to illustrate the problem.

If somebody gets an idea...
Thanks,
Thomas

[patmurris]

Can you be more specific as to what we are seeing in your screenshot - which layers are active for instance. Are you using one of the SDK example app or a more elaborate application of yours?

[m_k]

I think that you can get rid of those holes by enabling tiles struts or skirts (or whatever they're called in WWJ)... but don't ask me how
The missing tile at the bottom is another issue.

[damienpp]

I remember having similar problems where my elevation data wasn't interpolated or aligned properly. Also we had trouble when the tiles weren't a certain size (possibly 150x150, but I don't remember for sure).

[Peter Skvarenina]

Hi Thomas,

I had exactly the same problems when trying to use custom elevation and had solved them as you can see on the following thread:
http://forum.worldwindcentral.com/sh...ad.php?t=24024

I will give you some tips that helped me:

First, the holes on the tile borders might be related to the possibility that your tile borders aren't aligned properly - I had similar effects when the first/last column/row of surrounding tiles didn't match. They have to be the same.

Second, the disappearing tiles close to the viewpoint might be related to two things - first you might not have correct numbers of elevation levels set in your elevation model configuration file and/or your dataset has uneven number of levels on different parts of the world. Set it exactly to the number of levels you have - if you set it to a larger number the elevation lookup would fail and you would end-up with a flat tile. If the number of levels is lower in certain parts of the world, you would have to write your own graceful failover function that looks up elevation from levels above. The other reason for this problem might be bad matching of elevation extremes values to your tiling schema, forcing tile to be removed when computing set of visible tiles. You can try to work around this problem by redefining a few methods in the BasicElevationModel that return elevation extremes to some pre-defined range such as [-11000, 9000]. Also, another possibility is incorrect near plane computation for view frustum occurring in the BasicView class - this would however point to wrong elevation look-up (at least that was in my case).

Also, by default World Wind interpolates elevations of tiles to a grid of 23x23 points per tile. This explains why there are some strange artifacts when zooming in/out especially in areas with concentrated large elevation changes.

I was using completely non-standard size 129x129 as well as a different tiling schema (top level tile of 180x180 degrees, quadtree)

Hope some of these ideas would help you solve these problems!
Peter

[anaxa_gore]

Hi everybody and thanks for your answers,

Patrick, I am not using the SDK example.
In the screenshot, there is the BMNGOneImageLayer and a VMAP layer representing the terrain elevation lines. The VMAP layer is served through the Geoserver WMS, using the DDS plugin developped by what_nick (working very well...thanks !).
The elevation model is created from a geoserver WMS layer. This layer is generated from DTED data. This data has been converted into geotiff, then I created a pyramid from the generated tiff files. So I am sure that the first/last column/row of surrounding tiles match.

I am creating the elevation model in WorldWind this way :

av.setValue(AVKey.PIXEL_TYPE, AVKey.INT16);
av.setValue(AVKey.DATA_TYPE, AVKey.INT16);
av.setValue(AVKey.BYTE_ORDER, AVKey.BIG_ENDIAN);
av.setValue(AVKey.IMAGE_FORMAT, "application/bil16");

av.setValue(AVKey.NUM_LEVELS, 10);
av.setValue(AVKey.TILE_WIDTH, 150);
av.setValue(AVKey.TILE_HEIGHT, 150);

ElevationModel elevationModel = (ElevationModel) factoryElevation.createFromDataConfig(configuration, av);

getWwd().getSceneController().setVerticalExaggeration(1.5);
getWwd().getModel().getGlobe().setElevationModel(elevationModel);

I tried to change the NUM_LEVELS to 1, and I don't get any hole on the map, but the data resolution is then really bad ! 10 is the number of pyramid levels on the server.

When I launch my WW application, The cache folder is created and I get the attached XML file which describe the layer. Immediatly, I get the "getLayerExtremeElevations: GRAVE: Error parsing value", probably due to the fact that the

<ExtremeElevations/>

is not set... Is that important ?

Another thing : I can't understand the LEVEL_ZERO_TILE_DELTA...

If somebody gets an idea, il will be great !
Thanks again for your help,
Thomas

PS : I hope I give enough information...?

[anaxa_gore]

Ok so, I finally understood what Peter meant when he said :
"You can try to work around this problem by redefining a few methods in the BasicElevationModel that return elevation extremes to some pre-defined range such as [-11000, 9000]".
In fact, I didn't want to redefine any method so I didn't use this first.
But instead of redefining some methods, it seems that adding the following two lines when creating the elevation model do the same !

av.setValue(AVKey.ELEVATION_MIN, -11000d);
av.setValue(AVKey.ELEVATION_MAX, 9000d);

So now it seems to work fine !
I am going to try with other datasets to validate that everything is working !
Thanks again,
Thomas