Using the VTP Software

Very Briefly

The purpose of the VTP software is to allow you to rapidly construct an interactive 3D visualization of any part of the real world.

In Detail

The general process of building a visualization using the VTP tools is to import data files into VTBuilder, manipulate them in a content-specific manner, then export them into a series of runtime files.  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 use these applications.

BExtractor (Building Extractor) may be useful when you do not have building footprint or location data, but you do have some USGS DRG which contains the buildings.  It produces VT Structure files (VTST) which can be sent directly to Enviro, or processed further in VTBuilder.

Cropping and re-sampling Images

If you have imagery that you wish to drape, that does not matches your elevation in projection and extents, then you will need to crop and/or re-project it to match.  The VTP software does not have these features.  Here are some possible approaches you can use:

  1. If you happen to have it, many high-end software packages such as ERDAS Imagine can do these steps.
  2. The inexpensive software Global Mapper is capable of loading any number of images, displaying them with any given projection, and extracting a rectangular area (cropping).
  3. 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 -projwin option is useful for this purpose.
  4. Finally, if you only need to extract a rectangular area, it may be possible to use a conventional bitmap application like PhotoShop to crop to the area of interest.  This requires some manual arithmetic to turn coordinates into pixel values.

Using your own 3D Models

If you want to import your own, custom 3D models, there are several ways to do it.

  1. 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.
  2. Use Enviro to place models directly on the terrain with the mouse (menu Tools: Instances).
  3. 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:

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:

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.