A Primer for Creating 3D Models in ArcScene - Myweb @ CW Post ...

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FeaturesPart of one of three detailed AutoCAD drawings of the C.W. Postcampus used as a data source.A digital orthophotograph, showing a portion of the C.W. Post campus,that can be downloaded from the New York State GIS Clearinghouse.and verify features from the AutoCAD files. Thedata was separated into the 12 shapefiles listed inTable 1.was used as a hard clip line in the triangulationprocess. The resulting TIN honors z-values onthe contour lines; uses spot elevations (that wererepresented as two short, crossed line segmentson the contour layer in the AutoCAD drawings);and does not extrapolate z-values outside theedge of campus where detailed elevation datawas not available.Roads and sidewalks were mapped as polygonsrather than lines to control the width of theParking lots, buildings, and forested areas werealso mapped as polygons. Initially, these fivepolygon layers were symbolized with appropriatetextures and colors and overlaid on theTIN on which a grass texture had been applied.However, when using this method, portions ofthe grass-textured TIN bled through the otherpolygon layers that obtained base height fromthe TIN. The result was that odd patches of grassappeared in places such as in the middle of aMaking a Virtual CampusThe two-foot interval contour lines provideddetailed base elevation information for the entirecampus. The contours were converted intoa triangulated irregular network (TIN) to createa smooth, continuous surface across the campus.To create the TIN, the contours were used asmass points and the campus boundary polygonroads. This also allowed surface textures, such asasphalt and concrete, to be applied in ArcScene.parking lot where they were not actually present.Continued on page 28
Virtual Campus 101Continued from page 27This occurred even if the parking lot polygonswere offset from or extruded above the TIN.Because nearly every feature that wasnʼtroad, parking lot, sidewalk, forested area, orbuilding on the campus was grassy lawn, a landuse/land cover layer was created that assigned allareas on campus to one of these six categories.This eliminated the display of random, phantomgrass. Also, sharp edges could be displayed betweenadjacent features by offsetting one featuretype with respect to another. For example, theroads and parking lots were offset by 0.3 meter(or approximately 1 foot) from the sidewalks,grassy areas, and forested areas to create a discretewhite break between the two. In essence,this process created a virtual curb one foot high.By mapping the forested areas as polygons,points representing individual trees could begenerated at random locations within the polygons.In this model, points were generated usinga dot density display in ArcMap and exportedas a point shapefile using a script obtained fromthe ESRI knowledge base. Virtual forests for thiscampus were created using four different pointfiles, each with a different dot density. This resultedin random point placement and the abilityto use four different types of trees that producedforests with more variety: different species, sizes,and colors of trees.It was important for some point features to beoriented in a particular direction. For example,the bus stops had to face the street. To achievethis, a rotation field was added to the attributetable, using 0 to 360 degrees as the value range.Rotation values were entered for each featurethat needed adjustment and used to rotate the objectsin ArcScene.To give the buildings height, they were extrudedbased on height values from the attributetable. To capture the varying colors of theexterior walls, trim, and roofs of the buildings,two more copies of the buildings shapefile wereadded to the ArcScene project. The three identicalbuilding layers were then offset vertically sothey would be layered on top of each other. Theextrusion values for each copy of the shapefilewere also adjusted so the buildings would retaintheir correct height. The polygons were thensymbolized with colors, based on exterior colorvalues from the attribute table. The resultingvariations of colors match the general exteriorcolors for each building on campus.Adding More RealismTo add even more realism to the virtual campus,two additional shapefiles were created—onefor cars and one for horses. Cars were placed inthe parking lots, and horses were placed in thehorse stables located on the campus. ArcSceneincludes an array of three-dimensional objects,such as cars, trees, light posts, fire hydrants, andbus stops, that were used in this model. In thisrendering, five different makes, models, and colorsof cars (available in ArcScene) were used toadd variety and detail to the model. All cars wereoriented based on parking spaces on campus,with the necessary degree of rotation stored inthe Rotation field of the attribute table.Importing three-dimensional objects is simple.To add horses, points in a new shapefilewere scattered around the stables. These pointswere given various orientations specified in aRotation field in the attribute table. A free threedimensionalhorse model was downloaded fromthe Internet and added as a 3D marker symbol.Fences in the stables area are numerous, butwere easily included by saving line featureson the fence layer from the AutoCAD drawingas a shapefile and then applying a 3D textureline symbol representing a rail fence from theArcScene 3D symbols.Right: A portion of the 3D campusmodel that shows different land use/landcover features in close proximity. Theroads and parking lots are offset onefoot below the grassy areas, forestedareas, and sidewalks. A rotation valueis assigned to the bus stop to properlyorient it with respect to the road.Where to Go from HereAdditions and refinements can be made to anyvirtual model. However, it is possible the C.W.Post campus model may generate more interestand foster more participation on campus in itscurrent state rather than a more realistic version.Nonetheless, there is a long wish list of enhancementsfor this model. The use of three-di-Right: The stables on campus with a3D model of a horse included at severallocations. The complex pattern of fenceswas easily imported from the AutoCADdrawing of the campus. These fences canbe displayed with 3D texture line symbolsso gaps between the fence rails aretransparent.Right: Three copies of the buildingsshapefile were added to the displayand assigned colors to represent walls,trim, and roofs. Heights were extrudedso that the three building layers arestacked on each other and take into accountthe height of each building.28 ArcUser April–June 2005 www.esri.com
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