Constructing 3D Models for the Leschi Town Virtual Urban Environment
At MetaVR we create many of our own models of buildings and other structures for use in the databases that we build for our customers. This page describes the process we use to create 3D models of buildings. The images shown here are from a project in which we modeled buildings and other structures for the virtual Leschi Town MOUT site as part of MetaVR's Ft. Lewis database. This terrain is included in the Northwest region of the CONUS++ terrain.
Creating the model geometry
Working with 3D modeling tools and image-editing tools, we use data such as site photographs, maps, and elevations to make a basic 3D mesh with correct proportions and scale. In some cases, our task is to create generic structures that are appropriate for the virtual site or context in which the model will reside. In other cases, our task is to replicate real-world structures using photographs of the actual given buildings as the model textures. The image below and on the left is one of many site-specific photographs we used to create models for a given terrain database. The image to its right is a blueprint of the entire site, which we used as a guide to placing completed models in context on the terrain and to confirm the footprint of the 3D models.
Adding MetaVR model format features
MetaVR VRSG supports several features in MetaVR's 3D file format. These features enhance the model's realism in a real-time context, for example:
Photographing buildings for modeling
Textures for 3D models depend heavily upon the original photographs from which they are derived. Such photographs should to be taken in a perspectiveless manner, ideally with a digital camera of at least 6 megapixels at full resolution. Perspectiveless means that you take the photograph fully perpendicular to the subject. For efficient modeling, textures should be perspectiveless when we apply them to a model. Otherwise, removing perspective from a photograph is a labor intensive image-editing effort. Good and even lighting is also important; shadows as well as snow and dirt are aspects that obscure the normal state of the building to be modeled. (We add these environmental details after the model is built.)
Texturing the model
To make textures for our models, we edit the photographs, by adjusting the color and removing any unwanted interference and camera distortion. Shadows can be baked into parts of the texture to simulate soft lighting.
We place all the textures for the model into one larger composite texture
in 512 x 512 pixel allotments for efficient texture paging within VRSG.
Texture elements are tiled, or repeated, whenever possible to reduce
the memory requirements for rendering the model. Such textures are useful
in terms of marginal utility in that their visual content is generic;
some texture elements contribute more to the model fidelity than others.
We model textures that contain unique architectural information, such
as the facade of a building, as photo-specific. This means that there
is a one-to-one mapping of the photographic element to the model's geometry.
Inspecting the final model
When the model is complete, we convert it to MetaVR's model format file. (MetaVR currently provides tools for converting models in FBX and OpenFlight formats to MetaVR's model format.) We view the model in the MetaVR Model Viewer and then render it in VRSG. We inspect the model's switch states, material settings and artifacts in the geometry and make any needed corrections.
Finally, the model is reviewed by other members of MetaVR staff, and any necessary corrections or refinements are made.
Below and to the left is one is one of the photographs of the original building on which the model shown above is based; the building is located at the Ft. Lewis, WA, Leschi Town MOUT site. To its right is a VRSG screen capture of the model in its analogous context in the virtual world, that is, in a simulated view of the MOUT site within MetaVR's Ft. Lewis terrain database. We created the models of buildings and other structures for that database from a set of approximately 200 photographs of the Leschi Town area.