The purpose of the VTP software is to allow you to rapidly construct an interactive 3D visualization of any part of the real world.
The general process of building a visualization using the VTP tools is to load or import data files into VTBuilder, manipulate them in a content-specific manner, then save them into a series of runtime files. Some kinds of data don't need any processing, and can be used directly. The runtime files are placed into the appropriate Data directory, then Enviro is used for a realtime visualization of the data.
See the VTBuilder and Enviro documentation for the step-by-step process of reading your data in, and visualizing it. This includes elevation, roads, trees, buildings and fences. In addition to the documentation, there is a simple tutorial of how to get started with these applications.
Your data should be in the same coordinate system (aka. "projection"). VTBuilder can help you with reprojecting elevation if you need to; if you must re-project imagery, you may want to use another tool for that step. If you are technically savvy, the cross-platform open-source package GDAL provides a command-line tool called 'gdal_translate' which can be configured to re-project and extract rectangular areas. The
-projwinoption is useful for this purpose. In fact, the Windows installer of VTP includes all the GDAL utilities, so you probably already have them.
Extent (Ground Area)
If you have imagery that you wish to drape, that does not matches your elevation in extents, then you have two options:
- You can crop it to match. VTBuilder can help you do this.
- You can drape it in Enviro as an Image layer. The Image should be a GeoTIFF so that Enviro knows where to place it on your terrain.
The usual approach (one elevation file, one image file) works fine if your data is modest sized (up to around 4K * 4k) and is roughly square. But, if it is much higher resolution, or very non-square, then you will want to make a tileset. In fact there will be two tilesets: one for elevation and one for imagery. You will sample them with the same number of tiles, and the same extent, so that they match. Select your desired area with the Area Tool, use Match Tiling and Area to Layer to chose a tiling, then sample both your elevation and imagery using that tiling.
If you want to import your own, custom 3D models, there are several ways to do it.
- Use VTBuilder to import the location and filename of each model from a GIS data file. This is written to a VTST file which is loaded in Enviro.
- Use Enviro to place models directly on the terrain with the mouse (menu Tools: Instances).
- As a programmer, you can use the vtlib library to load models and place them in your scene. (vtlib: Importing 3D Models)
The object geometry file can be in any format recognized by the underlying OpenSceneGraph system and is typically generated in a 3D surface modeler or CAD system. Typical formats include:
- .3ds (the export format from Discrete's 3D Studio MAX application, also exported by AutoCAD)
- .lwo (Lightwave)
- .flt (OpenFlight format - with import/export plugin available for Alias|Wavefront's Maya)
- .obj (old Alias Wavefront format)
- .osg (OpenSceneGraph native format).
There is also support for some other formats, check the OpenSceneGraph website for a full current list, and limitations.
The content manager application CManager can be used to preview your models to see how they will appear in Enviro. CManager can also assemble multiple LODs (levels of detail) of a model into a single content item, assign scale/units for each model, and save the set of items to a content file (.vtco) for use in Enviro. This is useful if you have a lot of 3D models or LODs to manage.
In order to understand the relationship between the two types of file (VTST and the 3D model) it is helpful to view the structure file contents. The VT structure file is itself a type of XML file, and can be viewed in a text editor. It can contain references (by name) to instances of 3D models. The two types of files are placed in separate locations for runtime use:
- VTST files should go in a BuildingData folder, anywhere on your data path
- 3D object files can be located anywhere on your machine
Once you have the VTST files in place, they should show up Enviro Terrain Creation Parameters dialog under Culture: Structure Files. You can include as many VTST files as you like.