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FAQ
===
**Sections:**
* `Common Usage`_
* `Other Terrain Formats`_
* `Community and Support`_
* `Licensing`_
----
Common Usage
------------
How do I place a 3D model on the map?
.....................................
The ``osgEarth::GeoTransform`` class inherits from ``osg::Transform``
and will convert map coordinates into OSG world coordinates for you::
GeoTransform* xform = new GeoTransform();
...
xform->setTerrain( mapNode->getTerrain() );
...
GeoPoint point(srs, -121.0, 34.0, 1000.0, ALTMODE_ABSOLUTE);
xform->setPosition(point);
A lower-level approach is to make a ``osg::Matrix`` so you can position
a model using your own ``osg::MatrixTransform``::
GeoPoint point(latLong, -121.0, 34.0, 1000.0, ALTMODE_ABSOLUTE);
osg::Matrix matrix;
point.createLocalToWorld( matrix );
myMatrixTransform->setMatrix( matrix );
How do make the terrain transparent?
....................................
By default, the globe will be opaque white when there are no image layers, or when all the image
layers have their opacities set to zero. To make the underlying globe transparent, set the
base color of the terrain to a transparent color like so::
<map>
<options>
<terrain color="#ffffff00" ...
In code, this option is found in the ``MPTerrainEngineOptions`` class::
#include <osgEarthDrivers/engine_mp/MPTerrainEngineOptions>
using namespace osgEarth::Drivers::MPTerrainEngine;
...
MPTerrainEngineOptions options;
options.color() = osg::Vec4(1,1,1,0);
How do I set the resolution of terrain tiles?
.............................................
Each tile is a grid of vertices. The number of vertices can vary depending on source data
and settings. By default (when you have no elevation data) it is an 15x15 grid, tessellated
into triangles.
If you do have elevation data, osgEarth will use the tile size of the first elevation layer
to decide on the overall tile size for the terrain.
You can control this in a couple ways. If you have elevation data, you can set the
``tile_size`` property on the elevation layer. For example::
<elevation name="srtm" driver="gdal">
<url>...</url>
<tile_size>31</tile_size>
</elevation>
That will read data as a grid of 31x31 vertices. If this is your first elevation layer,
osgEarth will render tiles at a resolution of 31x31.
Or, you can expressly set the terrain's tile size overall by using the Map options.
osgEarth will then resample all elevation data to the size you specify::
<map>
<options>
<terrain>
<tile_size>32</tile_size>
...
----
Other Terrain Formats
---------------------
Does osgEarth work with VirtualPlanetBuilder?
.............................................
VirtualPlanetBuilder_ (VPB) is a command-line terrain generation tool. Before osgEarth
came along, VPB was probably the most-used open source tool for building terrains for
OSG appliations. We mention is here because many people ask questions about loading
VPB models or transitioning from VPB to osgEarth.
osgEarth differs from VPB in that:
* VPB builds static terrain models and saves them to disk. osgEarth generates terrain on
demand as your application runs; you do not (and cannot) save a model to disk.
* Changing a VPB terrain generally requires that you rebuild the model. osgEarth does not
require a preprocessing step since it builds the terrain at run time.
* osgEarth and VPB both use *GDAL* to read many types of imagery and elevation data from
the local file system. osgEarth also supports network-based data sources through its
plug-in framework.
osgEarth has a *VPB driver* for "scraping" elevation and imagery tiles from a VPB model.
See the ``vpb_earth_bayarea.earth`` example in the repo for usage.
**Please Note** that this driver only exists as a **last resort** for people that have a VPB
model but no longer have access to the source data from which it was built. If at all
possible you should feed your source data directly into osgEarth instead of using the VPB
driver.
Can osgEarth load TerraPage or MetaFlight?
..........................................
osgEarth cannot load TerraPage (TXP) or MetaFlight. However, osgEarth does have a
"bring your own terrain" plugin that allows you to load an external model and use it as your
terrain. The caveat is that since osgEarth doesn't know anything about your terrain model, you
will not be able to use some of the features of osgEarth (like being able to add or remove layers).
For usage formation, please refer to the ``byo.earth`` example in the repo.
.. _VirtualPlanetBuilder: http://www.openscenegraph.com/index.php/documentation/tools/virtual-planet-builder
----
Community and Support
---------------------
What is the "best practice" for using GitHub?
.............................................
The best way to work with the osgEarth repository is to make your own clone on GitHub
and to work from that clone. Why not work directly against the main repository? You
can, but if you need to make changes, bug fixes, etc., you will need your own clone
in order to issue Pull Requests.
1. Create your own GitHub account and log in.
2. Clone the osgEarth repo.
3. Work from your clone. Sync it to the main repository peridocially to get the
latest changes.
How do I submit changes to osgEarth?
....................................
We accept contributions and bug fixes through GitHub's `Pull Request`_ mechanism.
First you need your own GitHub account and a fork of the repo (see above). Next,
follow these guidelines:
1. Create a *branch* in which to make your changes.
2. Make the change.
3. Issue a *pull request* against the main osgEarth repository.
4. We will review the *PR* for inclusion.
If we decide NOT to include your submission, you can still keep it in your cloned
repository and use it yourself. Doing so maintains compliance with the osgEarth
license since your changes are still available to the public - even if they are
not merged into the master repository.
.. _Pull Request: https://help.github.com/articles/using-pull-requests
Can I hire someone to help me with osgEarth?
............................................
Of course! We at Pelican Mapping are in the business of supporting users of
the osgEarth SDK and are available for contracting, training, and integration
services. The easiest way to get in touch with us is through our web site
`contact form`_.
.. _contact form: http://pelicanmapping.com/?page_id=2
----
Licensing
---------
Can I use osgEarth in a commercial product?
...........................................
Yes. The license permits use in a commercial product. The only requirement is that
any changes you make to the actual osgEarth library *itself* be made available
under the same license as osgEarth. You do *not* need to make other parts of your
application public.
Can I use osgEarth in an iOS app?
.................................
Yes. Apple's policy requires only statically linked libraries. Technically, the
LGPL does not support static linking, but we grant an exception in this case.
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