Virtual Model Methodology

Tutorial video outlining the process from DEM to embedded virtual model.

Tutorial created using CamStudio software.

Data Acquisition

Grid Unit Data Download Process. A reference grid is used in order to assure that the correct files are downloaded from the MGC website. It is necessary for the project to insure that each site is covered by a 1000 meter buffer. The left shows the point representing the Arcola site along with its 500 and 1000 meter buffers. The reference grid is shown in red, labeled with the codes used by the data suppliers that allowed the researcher to only download the files that were necessary. The downloaded .zip files include five-foot resolution raster DEMs, one-foot elevation contours, and other data that are not necessary for this project.

Data Processing

Merge and Dissolve Process of Contour Files. Left: The separate units of contour files for each site were merged together, but the file retained its separateness in the divided contours. Right: After dissolving the file according to the contour elevation, the contour lines were finally cohesive, even across the grid lines. Merging and dissolving the contours increases the ease with which it can be handled.

Clipped Raster and Contour Elevation Data. Top: Elevation data clipped to 1000 meter buffers. Contour files for each site were merged ("Merge" tool) into one file, clipped ("Clip" tool) to the 1000 meter buffer. Rasters were merged with the tool “Mosaic to New Raster” and clipped with the tool “Extract by Mask” using the 1000 meter buffer layer as the mask. Bottom: Model used as a tool to input separate files of tiled contours that were merged, clipped to 1000 meter buffer boundaries, and dissolved.

These data were used to create various maps involved with the project.

Data Export

Models created for Merging and Extraction using Esri ArcMap's Model Builder. Top: Model used as a tool to merge separately tiled rasters and extract (clip) them to the 1000 meter buffers. Bottom: Model Used to Convert Raster DEMs from TIFF to PNG. This function could be used as a tool or copied for each site to all run at the same time. The model was used to convert the original raster DEM data from feet to meters (multiply by .3048) and multiplied again by 1000 (simply multiplied by 304.8 using Raster Calculator tool) in order to move the decimal point before converting the .TIFF file to a .PNG that allows for 16-bit integer only.

*Without multiplying the raster to move the decimal point, when the .TIFF is converted to a .PNG, all values are truncated at the decimal point, and the accuracy of the exported file to be used in modeling is greatly reduced. Therefore, the rasters are run through the raster calculator to multiply each value by 1000 to move the decimal point to allow for greater accuracy in converted values. At this time, the values were also converted from feet to meters because the program used to created the three-dimensional models from the rasters uses meters. For instance, the original value of a selected pixel is 176.860565, and the 16-BIT converted value is 176 with no changes made. Right: the original value is 135.213440 in feet, which when converted to meters is 41.213056512, and the value of the converted .PNG file 41213, allowing the value to be kept accurate up to three decimal places.

Terrain Import and Creation in L3DT

Importing a Raster DEM into L3DT. A heightfield is imported into L3DT in one of several formats, here using the 16-bit .PNG. After the file is selected, the horizontal scale is set to convert the 5 foot cell size to meters (multiplying factor of 0.3048). The new cell size for each pixel is 1.524 meters.

Adjusting the Vertical Scale in L3DT. To correct the vertical scale, open the vertical range window of the heightfield (under the Operations menu). Then move the decimal place so the value of 36575 meters changes to 36.575 meters. Because the Dornbusch and Haynes Bluff sites were factored by 100 instead of 1000, the decimal place for their heightfields only needed to be moved two spaces instead of three.

Cropping Height Map to 525 pixel Square. The initial heightfield images exported from ArcMap are large and round. Cropping them to exactly 525 by 525 pixels results in a more focused, square image with which to work in the modeling process.

Creating Light, Water, and Attribute Maps; Editing Attributes; and Generating Texture Map in L3DT. To create the various maps necessary to create the terrain texture, the Calculation Wizard is used. A: Select the maps that need to be generated. In this case, the water map, attribute map, terrain normal, and light map. B: The light map options are changed so that the direction of light is 330 (-30) degrees and the ambient light is a lighter shade, achieved by sliding the value bar toward the white at the top. C: The light map is set to use Water effects. D: The water map is set to flood the water plane at the elevation of the water for each specific site, found previously using the info tool in ArcMap. E: The attributes map is created using the Temperate (coastal) option so that a sand texture is used where the water is located, after the water map is generated. After the attribute map is generated, mounds cannot be distinguished (F). G: The attributes are edited in the Sapphire 3D window. Cliff texture is painted on the slopes of the mounds to help distinguish them from the surrounding ground. H: The texture image is generated under the Calculations menu. The only default setting changed is the image size. Create a tiled image with one tile sized 2048 pixels, the largest size allowed in the free version of L3DT. I: The final generated texture for the terrain. The shadows are added to the texture image from the light map that was generated earlier.

Terrain Mesh Export and Web Embedding

Exporting an Optimized Mesh from L3DT. Under the File menu, choose Export>Export optimised mesh. After the file name and .obj file type are selected, the Max. error tolerance needs to be lowered to 0.1 while the remaining options are default. On the right is the model preview.

Model Viewer Embed Script from Sketchfab. Using a free Sketchfab account, upload the mesh to your dashboard. In the model viewer, mouse over the link button on the far left and click the Embed button that appears. Copy the embed text from the window that appears, and paste it into the HTML editor window of the Google site editor, which is opened by clicking the HTML button while the page is in edit mode.