Designing a Show tent

With just 41 faces, the Show Tent is a good example of an object that is easy to build out of panel material like plywood. Yet such an object is difficult to design without a computer program such as L3DD. It has been stretched in both the X and Y directions, resulting in a more practical and pleasing structure than a conventional geodesic dome. The Show Tent would certainly make a very striking display pavilion at a conference or trade show. A smaller version makes a kid’s cubby house (see Physically Building Objects).

If the shape is deemed unsatisfactory, it can be tweaked by moving individual vertices with both the XY and YZ mirrors in place

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1.	Click on the New button to clear the decks for a new project.

2.	Select the Icosahedron from the Object Menu.

3.	Click on the Select All button and then the Quadrate button. The icosahedron immediately changes to an 80-face geodesic sphere.

4.	Click on the Create Cutting Plane button to create a square face on the groundplane (zero azimuth & inclination).

5.	Click on the Reverse Faces button to reverse the facing of the groundplane face (shiny side down).

6.	Click on the Truncate Object button to remove the lower half of the geodesic sphere.

7.	Click on the Face Numbers button to show all the face numbers.

8.	Shift-click on faces 1, 9 and 11, which all meet at the Z axis. Press the ‘Del’ key to delete these three faces to create a door.

9.	Now delete the floor of the dome and click on the Clean Up button to remove the isolated vertex and renumber faces and vertices.

10.	Click on the Vertex Numbers button to show all vertex numbers and on the Vertex Handles button to show vertex handles.

11.	Click on the X-Y Mirror and Y-Z Mirror buttons to invoke the two vertical mirror planes.

12.	Select vertex 25 (groundplane, 1 away from door) and move it radially with the multiply (asterix) key until its radius in the Status Bar reads just over 100 units. By reflection, vertices 26, 27 and 28 move in sympathy to create a more circular base to the dome. Turn the mirrors off again.

13.	Now select the Stretch in XYZ command from the Tools Menu (no button for this). The adjacent dialog box appears.

14.	Choose an X stretch factor of 1.2 and a Y factor of 1.4. Leave Z as 1.0. Click on Do It! Button to create the final Show Tent.

15.	A much easier way to obtain the show tent is to open the supplied L3DD file, ‘ShowTent.lig’.

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