The Grand Canyon in 3D | Landscapes

The Grand Canyon in 3D
The Art & Science of Visualization

BLM Resource Tools Conference 2003

	Grand Canyon National Park covers almost 5000 square kilometers and most of the last 2000 million years of geologic time, nearly half the age of the planet.

	Standing on the rim, visitors marvel at the scenic beauty but catch only a glimpse of the canyon's greater secrets.
	Some descend into the canyon depths and gain a new perspective, but may emerge with no greater understanding.
	Computer-based imagery frees us from the limits of ground based observation and allows us to change the ways in which we view and interpret the topography.
	This virtual Grand Canyon was built and rendered in Visual Nature Studio, a GIS terrain visualization and animation software package from the talented folks at 3D Nature in Arvada, Colorado. To find out more, visit them on the web at www.3DNature.com. All data was obtained from public sources on the internet. This is a typical project in the world of documentary and reconstruction illustration. Funding for a few days of work and heavily reliant on an artist who is also a scientist and historian.
	This northwest looking perspective view of the Grand Canyon area covers longitude 111.7 to 112.5 degrees west and latitude 36 to 36.5 degrees north. The terrain is lit by 10 am April sunlight. The terrain was generated from 28 U.S. Geological Survey SDTS data files. We're looking at more than 43 million data points on a 10-meter grid. Rendered at the lowest level of detail, this includes more than 87 million polygons. At the highest level of detail, there would be more than a billion polygons! This 1024x768 image rendered in less than 30 minutes on a 1.2 GHz Athlon PC.
	As with any good story, we need an establishing shot. While the view we have may show the terrain, it isn't very exciting. We're fortunate in Arizona to have online access to the Arizona Regional Image Archive, or ARIA, at the University of Arizona. You can download everything from digital versions of USGS topographic maps to Landsat imagery. Here, Landsat bands 3, 2, and 1 were combined in Photoshop and color corrected to create a 150 Mb composite image.
	Image metadata provided UTM georeferencing information that made it easy to import, register, and drape the image over the terrain. This works great for natural looking terrain from higher camera elevations.
	Here's a planimetric view. Let's drop the camera down and look north over Grand Canyon Village. Grand Canyon Village is on the South Rim near the middle bottom of this render.
	We can see the Bright Angel Canyon where the Bright Angel Trail starts from the South Rim. It descends into the Devil's Corkscrew and Granite Gorge, crosses the Colorado River, and climbs as the North Kaibab Trail to the North Rim. It's about 6.5 km from the lower left to the lower right.
	That's all well and good, but there's more to the canyon than just scenic vistas. Rock strata exposed here cover almost 2 billion years of geologic time and are fairly undisturbed as geology goes.
	This geologic map by George H. Billingsley is from the USGS Geologic Investigations Series I-2688. The vector map was rasterized to a 250 Mb high-resolution image. The map covers 60 minutes of longitude, 30 minutes of latitude, and was easily georeferenced.
	Here's the Grand Canyon Village view again with the geological map overlay. We can now see the Bright Angel Fault, the structural feature that led to the development of Bright Angel Canyon. While it may be interesting to geologists, it's more than a little confusing for the typical viewer.
	Here, we've removed the color map from the render equation. Rock unit colors tint the terrain according to a simplified stratigraphy, making the basic geology easier to read. There are two structural geology factors we had to take into account when applying this ground texture scheme. First, there was vertical movement along the Bright Angel Fault, so contacts between rock units have different elevations on the east and west sides of the fault. This was remedied by creating separate vector-bounded ground effects on each side of the fault and adjusting their respective elevations accordingly. The second factor is that although the rock layers appear to be horizontal, they actually dip a little to the south on this side of the uplift. To illustrate this, let's drop a camera down into Pipe Creek Canyon looking north. Pipe Canyon is in the lower right quarter of the image.
	This north facing camera is hovering above the Tonto Plateau east of the Bright Angel Fault. The rendered contacts between colored rock units are horizontal. You can see that terrain feature contacts, like plateaus and cliffs, increase in elevation northward up the canyon.
	Introducing an increase in contact elevation with increasing latitude gives the strata just the dip we need. The rendered rock unit contacts now follow the terrain contact features.
	Colors are an excellent tool for setting scene parameters and, in this case, illustrating simplified geology. Let's replace the simple geologic time-coded rock colors with color textures more suggestive of the rocks themselves.
	Next comes bump mapping to lend a subtle 3-dimensional textured look. As you relate these rock textures to the real world, don't worry too much about the textures on shallow slopes and plateau benches. These will be covered with vegetation by the time we finish the project.
	Lowermost in the the geologic column is the Vishnu Schist, a dark metamorphic rock more than a billion years old. It is shown here in the Inner Gorge looking downstream from Plateau Point. It's marbled appearance comes from veins of lighter colored rock, the Zoroaster Granite.
	A marble-based procedural texture was used to simulate the Vishnu Schist in VNS.
	Next up is the Cambrian age Tapeats Sandstone, laid down in the shallows along an ancient coastline. It's fairly resistant to erosion and forms cliffs. Here we're looking southeast into the Devil's Corkscrew and Pipe Canyon. The Tapeats Sandstone rests unconformably on the Vishnu Schist above the center of this slide.
	This is a closer view from the South Kaibab Trail. The rock shows distinct stratification and vertical jointing. The cliffs are vertically stained from millions of years of outwash from the overlying sediments. The virtual Tapeats shows similar stratification, jointing, and vertical staining.
	As the shoreline migrated east, the water deepened and the muddy Bright Angel Shale was deposited. Shales are easily eroded and form slopes in the Canyon. You can see it cross the center of this slide, a view northeast from the Grandview Trail. The Tapeats Sandstone, Bright Angel Shale, and Muav Limestone make up the Tonto Group and take us up to about 500 million years ago.
	The cliff-forming Mississippian Redwall Limestone derives its color from the Supai sediments above it. This northeast facing view was taken from Desert View.
	Like the Tapeats Sandstone, the Redwall Limestone shows heavy staining from Supai outwash above it. Colors include white calcium carbonate deposits, gray limestone, vertical streaks of brown Supai staining, and the deep browns and blacks of desert varnish. These colors are interrupted where sections of rock have separated from the cliff in blocks or arcuate spalls.
	The Pennsylvanian Supai Group includes sandstones, mudstones, limestones, conglomerate, and gypsum. It forms a steep broken slope. It's virtual counterpart reflects the different strata, both in color and bump mapping. Subtle vertical color variations simulate detritus slopes.
	While the Permian Hermit Shale tops this group but doesn't geologically belong to it, I've included it because its color and texture is similar.
	The Coconino Sandstone was an extensive coastal dune sea that covered the 4 Corners region in Permian time. Cross-bedding etches the surface; brown and gray streaks vertically stain it.
	It's topped by the slope forming Toroweap Limestone and cliff forming Kaibab Limestone, both of Permian Age. This view from Maricopa Point looks back toward Grand Canyon Village and the top of the Bright Angel Trail.
	The Kaibab Limestone is well exposed along the South Rim, here at Grand View.
	That closes out the Paleozoic Era in the Grand Canyon and takes care of the geology lesson. Now it's time to start growing things.
	With Visual Nature Studio, we have 3 ways we can add Ecosystems: unbounded using Rules of Nature (TM), vector-bounded Ecosystems, and via Color Maps. Which method you choose depends on your project goals as well as what data is available and how long you have to create the scene.
	The first option is the easiest to set up and reflects a perfect world approach. You set the rules for ecosystem placement and the software does the work for you. You choose factors like the upper elevation limit, slope range, and foliage type and density, to name a few.
	This is great for idealized scenes when no other data is available. Five Ecosystems or life zones were used for this scene. From the bottom up we see the Lower Sonoran, Upper Sonoran Grassland, the Upper Sonoran Piñon, Transition, and Boreal Forest ecosystems. This technique is great for attractive illustrations, but isn't a good choice for real-world accuracy. Rules, no matter how well developed, can't reproduce the chain of random and manmade events that culminate in the scenes we see around us.
	Which takes us to the second option. Vector ecosystems can be imported and used to place foliage assemblages. Even better are ecosystem shapefiles with attributes defining the ecosystem type, density, and height range. These can be used to automatically populate a scene containing hundreds or thousands of vectors.
	Here's a section of Yellowstone National Park. A great deal of GIS data is available online at the Wyoming Natural Resources Data Clearinghouse, mostly as a result of individual projects at the University of Wyoming. The red lines are shapefile vectors. Colors represent shapefile land cover classifications, by primary and secondary landcover type. Each shapefile contains density information for the vector area which is used create foliage densities in the final render.
	A Color Map can be used to drape an image over the terrain, like the geologic map we used earlier. Colors in the map can also be used to place Ecosystems. And we just happen to have one suitable for the task at hand.
	This is the National Land Cover Data, or NLCD, image for Arizona. This data is part of a cooperative project between the USGS and US EPA and is based on 30-meter Landsat thematic mapper (TM) data. It's a 450 Mb Geo-TIFF with georeferencing embedded in the file.
	Here's a planimetric view with the NLCD image draped as a Color Map to color the terrain. Each color in the image represents a class of land cover.
	In the Grand Canyon Village view, we're close enough to the image that we can see pixels, which may take something away from the idyllic canyon scene we're trying to create. Once we assign Ecosystems to colors, we'll randomize these edges and no one will be the wiser. The 5 canyon Ecosystems were assigned to their respective land cover class colors in the NLCD Color Map.
	When rendered, the Ecosystems were placed according to their respective colors in the NLCD Color Map. I took some creative license and assigned the residential and commercial area colors around Grand Canyon Village to natural Ecosystems. Render time: 20 minutes.
	Now for the inner canyon view with same NLCD Ecosystem distribution.
	Atmospheric haze is added to further enhance realism. Haze has lightened the dark rock to the intensity we're looking for.
	The Grand Canyon Village view, complete with haze.
	For comparison, here's an early morning spring shot from an overlook at Grand Canyon Village. As long as we're here, let's take a side trip east to Wupatki National Monument.
	Around 1064 AD, according to tree-ring dating, Sunset Crater erupted north of modern- day Flagstaff, Arizona. The eruption left a blanket of cinders and ash across the high desert region, including the area now bounded by Wupatki National Monument. These deposits made limited farming possible and attracted a melting pot of cultures to the previously uninhabited area.
	It is estimated that several thousand people lived in the area during the 12th century until soil fertility gave out. Wukoki is one of several Anasazi and Sinagua structures dotting the area. This is a modern day view of the pueblo site, less the pueblo ruins. Yet another example of a project that only had funding for a few days of work.
	1100 AD. Close your eyes and drift back 900 years. According to pollen studies, the climate was wetter. We've increased the understory grass and bush density, added a few oak trees, increased the overstory piñon pine height, and added ponderosa pine. Oak prefer more moist soil so we restricted it to locally depressed areas in the terrain.
	1150 AD. Pueblo construction is finished. This model was designed to blend in with the established landscape illustration style. The rocky outcrop on which the pueblo sits is also a 3D model created in LightWave, imported into World Construction Set, and textured to match the surround terrain.
	This comparison view looks northeast along the east plaza wall toward the main pueblo structure.
	1150 AD. Here's the 1100 AD view with the pueblo in place. Yes, you guessed it, all that work to put an itty-bitty pueblo into the scene. :)