EnVision -- Environmental Visualization System

	EnVision -- Environmental Visualization System
	A product of the USDA Forest Service, Pacific Northwest Research Station

Overview

EnVision is designed to be a full featured rendering system for stand- and landscape-scale images. Applicable projects range from a few to several thousand acres. The system is built upon many of the original concepts used to develop the Vantage Point visualization system. However, EnVision does not attempt to model changes to the landscape over time.

Basic components of an EnVision project include a digital terrain model to define the ground surface, color and texture maps to define ground surface characteristics, and groups of objects or "actors". Scene definitions include background imagery used to add clouds and distant landscape features, model components (e.g. terrain model(s) and polygon overlays), viewpoint and camera characteristics, and foreground imagery used to provide high detail in the image foreground. EnVision models individual light sources including a simulated sun position and atmospheric effects such as fog and haze. EnVision renders images using a geometrically correct camera model making it possible to match real photographs taken from known viewpoints to simulated scenes.

Model Definition.

An EnVision model includes the following components:

digital terrain model
ground texture and color maps used to describe ground surface characteristics
polygon, line, and point data used to locate ground surface textures or object sets
object sets used to represent populations of trees or individual objects such as buildings

Scene Description

In addition to the EnVision model, a scene includes the following components:

background image(s) used to provide elements such as clouds and distant scenery
light sources and characteristics
camera characteristics and location
atmospheric effects such as fog and haze
foreground image used to provide foreground detail

Computer System Requirements

EnVision is designed for the Windows 95 (OEM b or later), 98, and NT (version 3.51 or later) operating systems using OpenGL. Early releases of Windows 95 may require addition of the OpenGL libraries before EnVision can operate. EnVision requires at least 64 Mb of RAM. It operates best on systems with 128 Mb or more. For best performance and display quality, systems running EnVision should be configured to use at least 16-bit color. 24- or 32-bit color are preferred. EnVision supports image rendering so high-quality images can be produced on systems using less than optimal display configurations. Disk space requirements for the EnVision software and related files is not excessive. However, saved images can become quite large when saved using an uncompressed image format such as Windows bitmaps. JPEG, or other, compression can dramatically reduce image size but may result in some loss of quality.

Project Status

EnVision development started in December 1998. Initial development efforts were focused on the development of fundamental rendering techniques using OpenGL as implemented on Windows platforms, the overall user interface to model components, and further refinement of the EnVision design. The early prototypes, mid January 1999 demonstrated most of the features desired in a final version but lacked connections to "real" databases. Efforts in February 1999 focused on methods for rendering large numbers of objects (trees) efficiently and linkages with databases containing polygon, stand, and landscape attributes. A prototype version for release is expected during the summer of 1999..

Example EnVision Images

These images are screen captures from EnVision. Some of the images were captured while operating in 16-bit color mode and as a result show some color "banding".

	The basic EnVision interface consists of an outline view of the project and switches to control rendering of individual model components.
	Model components are specified using a property sheet control.
	EnVision's relies on digital terrain models to represent the ground surface. A variety of rendering options are available including simple wire frame mesh, shaded surface, shaded surface with mesh (shown at left) or contour lines, and textured surface.
	EnVision uses simple images to model ground surface characteristics. In this image, an unrectified aerial photo is draped over the ground surface. In most cases, such applications would use a rectified image but EnVision can use texture patches applied within polygon boundaries to represent ground or vegetation characteristics. In this image, the grid has been superimposed over the ground surface to enhanced the terrain shape.
	This image shows a texture surface rendering without the surface grid. The version of EnVision used to create this image only models diffuse light so terrain features tend to "wash out". Later version of EnVision will allow point light sources to better highlight terrain features and to simulate the appearance of the landscape through various seasons and times of day.
	EnVision allows background image to further enhance image realism. Background image could represent clouds as in this image or background scenery.
	EnVision models populations of trees using a range of rendering techniques. This image represents trees using actual tree photographs mapped onto individual polygons. There are three types of trees in the image and the ground surface has been textured using a scanned aerial photo.
	Another image using tree icons. This image also uses a background image to produce the clouds.
	One more image using tree icons.

This page was last modified on Feb 24, 1999

If you have comments or need additional information, contact Robert J. McGaughey at the Pacific Northwest Research Station (mcgoy@u.washington.edu ).