3D Modeling of Greytown, Nicaragua

A MicroStation Exercise

These materials were developed by Peter H. Dana and Shannon Crum, Department of Geography, University of Texas at Austin, 1995. These materials may be used for study, research, and education in not-for-profit applications. If you link to or cite these materials, please credit the authors, Peter H. Dana and Shannon Crum, The Geographer's Craft Project, Department of Geography, The University of Colorado at Boulder. These materials may not be copied to or issued from another Web server without the authors' express permission. Copyright 1995. All commercial rights are reserved. If you have comments or suggestions, please contact the authors or Kenneth E. Foote at k.foote@colorado.edu.


This page is available in a framed version.  For convenience, a Full Table of Contents is provided.

This exercise is designed to familiarize the student with simple 3D modeling techniques, rendering, camera views, and fly-by animations, using MicroStation.

Greytown (also called San Juan del Norte), Nicaragua was a settlement at the eastern terminus of one of the proposed canal routes across the Central American isthmus during of the nineteenth century. The town was a small fort and customs station prior to 1848, the start of its period of rapid growth as a foreign merchant enclave. During the California Gold Rush, thousands of travelers crossed the isthmus through this town on their way to or from San Francisco. Sail and steam-ships traveled between Greytown and New York and New Orleans. Small boats transported passengers along the Río San Juan - Lake Nicaragua waterway. Mules and horses transported them across the short land section between the lake and Pacific ports, meeting ships traveling up and down the coast between California and Nicaragua and Panama.

 At the outlet of the Río San Juan, the town was built in a rapidly changing physical environment. The surrounding delta, built from the volcanic sediment carried down from the Costa Rican volcanoes to the southwest and interacting with the prevailing ocean currents and winds, filled the harbor with shifting sandbars and spits, continuously changing the landforms.

 In 1854 the town was bombarded and burned by a U. S. war-ship during a confrontation with the townspeople over tariffs and control of the transit route. During the period between 1848 and 1854 and afterward while the controversy over the destruction of the town was reported around the world, the town was described and depicted in a variety of charts, illustrations, and texts. These descriptions exhibit a wide range of differences in their portrayals of Greytown.

GIS technologies can provide a method for evaluating differences in place description in an environment that experienced rapid growth in settlement patterns and simultaneous variations in landforms. In this exercise, a planimetric map will be used to produce a three dimensional model that can be compared with oblique and horizontal perspective illustrations (panoramas and bird's eye views) from different periods.

The plan map is from a September 1851 survey of the harbor by Orville W. Childs, chief engineer for the American Atlantic & Pacific Canal Company. The first panorama shows the port in 1849 as portrayed in Squier's Nicaragua (1852). The second panorama was published in 1851 by Felipe Molina, a minister of Costa Rica. The second Squier view shows Greytown in 1853. The last panorama portrays the burning of the town in 1854 and was published in the London Illustrated News within weeks of the event. The object of the exercise is to produce panoramic views from the planimetric map and compare them to these four panoramic views of the town.

 The town was re-built and remained a small settlement until it was bombarded and destroyed again in a Sandinista-Contra conflict in 1984. A new town has been built a few kilometers to the northwest and is called both New Greytown and Nuevo San Juan del Norte.



3D Modeling of Greytown, Nicaragua

MicroStation Procedure Guidelines

Launch Microstation

 Double click on the Microstation icon in the Program Manager window or under the Start/Programs/Microstation95 directory if using NT 4.0. Your screen should look like this:
 
 

Create a New Design File

 In the MicroStation Manager window, first change the Style at the bottom to Command Window. Next click on File and select New. A window called Create Design File will open on the screen. In the textbox, type "greytown", then click once on the Select button and choose seed3d.dgn from the scroll menu; "seed3d.dgn" will appear in the Seed File dialog box. Click OK and OK again to return to main Microstation window. Click OK once more to open the new 3D seed file.


Fit View

 Observe the three dimensions in the top, isometric, front, and right views by choosing the fit view tool and clicking in each of the four windows.

 Remove the Seed Design

 Place a fence around the 3D seed design and delete the contents of the fence by choosing the delete tool and clicking inside of the fence.
 
 
 
 
 


When you complete the project, your levels will contain the following elements:
 
  Be sure to keep your design elements in the correct layer. It will be important later when you are assigning textures to your three-dimensional representation of Greytown. If elements are created in the wrong layer, simply move them into the correct layer using the Change Element Attributes tool. 

 Before you get started, review the functions of the main toolbox and the MicroStation Command Window.


Importing a Raster Image

 To begin adding elements to your design file, Set the active level to level 1 by selecting Settings from the Menu Bar. Select Level then Display from the pull-down menu. The View Levels window will appear. Double click on level 1, then click apply.

Now, Import a raster image of the Childs' 1851 map of Greytown into level 1 and register it as a 1400 meter by 1000 meter rectangle. The image is available on the anonymous ftp site on Austin. To retrieve it, log into austin.grg.utexas.edu using the anonymous login. Go to the GTOWN directory and ftp the file childs.tif to your disk in binary format. Alternatively, the files can be obtained from the download directory by clicking on each file while holding down the shift key. Once you have the .tif image on your disk, select File from the command window and click on Import, then Image.

In the window that pops up, set the Filter Format to tif, and select the file a:\childs.tif In the precision input (text) window of the MicroStation Command Window, enter xy=0,0 as the starting point and xy=1400,1000 as the end point.
 
 


Creating a Water Surface

 Begin by checking to see if the Primary Tools bar is visible at the top . If not, go to Tools under the Menu Bar at top and click on Primary. If the menu is not at the top and appears in the middle of the screen as an individual window, select the window, and drag it to the top, and release it on leftover background grayspace. This should place it as a fixture to the page rather than as a movable window that must be constantly shuffled about.

 The next thing you need to do is produce a blue background representing water. First, set the active color to blue. Do this by selecting the color tile in the Primary Tool Bar. Make sure no other elements are selected then select the color blue on the top row of the color palette. Blues chosen from other rows will look OK on your screen, but may not print correctly.

Before you actually draw in the water, you need to set the active level to Level 3. Remember that this is the level designated for water. It may be helpful to turn Level 1 with the raster image off.

Next, you are going to Place a Shape. You will do this by selecting the Place Block tool from the main toolbar (see the illustration at the right for the correct tool). In the Place Block window, select Orthogonal for Method, Solid for the type of Area, and Opaque for the Fill Type. This will produce a solid blue water surface. Double check to make sure the Fill Color is 1 (blue). When the Microstation Command Window gives the instruction to "enter first point", type xy=0,0 in the text-input window. For "enter opposite corner", enter xy=1400,1000. There should now be a blue rectangle placed on the screen at the same coordinates as the raster image of Greytown. Turn on Level 1 to double check the coordinates correspond and that they overlay one another; then turn it off again. If the blue rectangle does not appear filled, click on Settings in the Menu Bar, then View Attributes. In the View Attributes window click the Fill box to turn on and then Apply (Apply will affect the window in the View Number box at the top, and All will affect all windows open). When done with the water surface, turn fill off again for later steps in the exercise.
 


Creating Land

 Now you should produce the green land areas. First, set the active level to level 5, the land level. Set the active element color to green using the same procedure outlined above. Make sure the Top View (View 1) is visible and maximized. Click on the Fit View button  to refresh the window and display the full extent of your drawing. Now, select the Place Shape tool from the Polygon toolbar (where Place Block tool is located) and trace the three land areas over the .tiff image using your mouse. Click on Close Element in the Place Shape window to close each land shape. If too many vertices (digitizing points) comprise the line, the shape may close prematurely. Use judgement when digitizing.


Creating 3D Land Solids

 The next step is to form 3-dimensional land solids that are three meters tall. These 3D solids will be the landshapes of Greytown in your final 3D animation. You can create files with solids of different heights, but for this exercise, we will make all the green areas the same height.

 To create the solids, select Tools from the Microstation Menu Bar. Select 3D from the pull-down window then 3D again to choose the 3D tool bar. In the 3D tool bar that appears, select Construct Surface of Projection Select each of the three land shapes with the Construct Surface of Projection selecting crosshairs  and define the height in the Command Window as xy=,,3.


Creating Structures (Buildings)

 Now you need to produce solid shapes for each structure on the .tiff image. Set the active level to level 7 and set the element color to red. Once again, select Tools from the Microstation Menu Bar, and select 3D from the pull-down window that appears. This time, select Primitives. Then select the Place Slab tool.  For Type select Solid. Trace the length and width of each building in the .tiff image (trace within lines to counter the effects of image capture). Then, in the Command Window, define the height as 5 meters (xy=,,5). You may want to use 6 meters for larger structures.


Moving Structures

 The next step is to Move the structures you just created to the land surface.

 View only level 7. In top view (view 1), select all the structures with a marquee selection (hint: draw marquee selection box with normal selection arrow icon button by clicking, holding left mouse button, and dragging box to desired size and shape). Choose the Move tool  from Tools/Main/Manipulate pull-down menus or by selecting the tool button from the main toolbar. In the right view (view 4), select an xy definition (a line) from the top of one structure. Define the height in the Command Window (text input window) as dl=,,3

 Change color of all the structures to white. Select all the structures by using a marquee selection. Then, change the active color to white. Make sure the raster image in Level 1 is off.


Render a Three Dimensional View

 Select the isometric view (window 2), maximize, and fit view. Select Utilities/Render/Phong and click in window 2. A default rendering of the surfaces will appear. You may want to experiment with other renderings. Once materials are assigned, renderings will appear more realistic.


Assign Materials

 Next, is assigning materials to the water, land, and structures. Click on Settings in the Menu Bar, then Rendering, Assign Materials. In the Assign Materials window, click on File and Open Palette. The Open Palette window provides a list of .pal files each containing various materials that have been grouped by category. We will start with the water since there are only two choices to choose from. From the Open Palette window scroll down and select water.pal, and click ok. In the Assign Materials window/Palette panel two materials should appear: Water - lake and Water - pool. Select one to preview in the Display panel to the right. Change Display view from Sphere to Rectangle for a more two dimensional view. Once the material for the water has been selected (highlighted in black), click on Tools. Under the Tools pull-down menu two different options for Assigning the material are available: Assign and Assign By Selection. Assign uses levels or colors to assign the material, and Assign By Selection uses the selecting crosshairs to manually select the element that the material is to be assigned to. Choose the Assign By Selection and click on the blue rectangle representing water. Click on the rectangle once more to accept the material. The assigned materials will be displayed in the Material panel to the left of the Assign Materials window. Now check the material by rendering Window 1 or 2.

If the material does not appear on the element as it did in the Display panel you may need to adjust the scaling. This is a common problem with the water - lake material. To do this, select the material and click Tools and Edit Material. If using water - lake material you may want to try an X and Y scaling value of 800 to 1000. Render water again and adjust as needed. Water - pool is also sometimes used as a replacement.

 Repeat steps for assigning the materials to the structures and land surfaces. When done assigning materials, choose File within the Assign Materials window to Save Material Table.


Global Lighting Optional

 If you choose to alter the lighting to make the rendered design file lighter or darker for example, you will need to click on Settings, Rendering, and Global Lighting. When the Global Lighting window appears, click on the Solar box to activate. The colors for the various lighting options can be chosen to the far right. If you wish to change the Time of day the lighting simulates or the Location (Latitude and Longitude), click on the Lock box and turn this off (empty box). This will allow the Time and Location options to be changed. Once the options are chosen, click in the visible rendered window to view the changes.


Produce a FlyThrough Animation File

 The final step is producing the animated flythrough of Greytown. First, set the active level to 9, the level reserved for the flythrough path. Next, set the color to yellow. From the Linear Elements toolbar choose Place Point or Stream Curve and place a line around Greytown; this will be the flight path. It is recommended, at first, drawing a 2D path in View 1, the top view, for simplicity purposes. After becoming experienced with the process, you may want to experiment by changing the flight path on the Z axis (the 3rd dimension). After drawing the flight path, choose the Move tool, select the flight path line, and in the Command Window type in dl=,,50 . This will raise the flight path above the town which will provide a birds-eye view.

Now the path has been created; it must be selected. Click on Utilities, then Render, and FlyThrough. In the FlyThrough Producer, Camera Settings panel, check that the Standard Lens is Normal and Target Position is Fixed. The Output panel can be experimented with in later attempts but during the first, leave View as 1, Shading as Phong, and Stereo clicked off. In the Output panel leave the number of frames at 10 unless otherwise specified in class. In the Tools menu of the FlyThrough Producer choose Define Path. In the Command Window, "Identify Element at Path Beginning" will appear. Select the flight path at the point with which you want the flythrough movie to begin. Next, "Accept Element at Path End" will appear; choose the end of the flight path. Lastly, the focus point (target point within the village) of the camera must be chosen when "Define Target Point" appears in the Command Window. Clicking somewhere in the middle of the town usually works best.

The views in some windows may change as the camera views are calculated. These views can be updated to the original view with the Rotate View tool.  Select the tool for the respective window and change Method from Dynamic to the original view: window 1 - Top; window 2 - Isometric; window 3 - Front; window 4 - Right, and click in the window.

 At this point, turn on all levels and views 1, 2, 3, and 4. Your file should look somewhat like this.

 Now its time to record the FlyThrough movie. Leave the FlyThrough Producer window open and in the View Levels window, turn Level 9, the flight path, off so that it does not appear in the movie. Return to the FlyThrough Producer and click on Tools and then Record. In the Record Sequence window change the destination drive to the a:\ drive, the Format to FLI, and name your file: greytown.fli. When you're done, click on OK. It will take a minute for the computer to record the movie.


View movie (within MicroStation)

 Pull down the Utilities menu and select Image, then select Movies from the pull-out menu.
 
 

The Movies window will appear.

Select File then Load. The Load Movie window will appear next, select yourfilename.fli.

 Click on the highlighted arrow to begin the movie. To slow down the playback of the movie, click on Settings and Playback from the Movies window. Change the Speed (Ticks/Frame) to 15 or 20 and hit the enter key.
 

If the animation needs improvement, repeat above steps, and do not be afraid to experiment.

 The 3D animation project is now (hopefully) complete.


Revised June 25, 1997. Lance Christian.
Last updated 2000.4.1. LNC.