
To rotate the scene, you have to place the mouse pointer over the left area of the applet and then, keeping the mouse left button pressed, drag it. To enlarge/shrink the scene, you have to place the mouse pointer over the left area of the applet and then, keeping the mouse right button pressed, drag it. Doing the same operation with the mouse middle button translates the scene. To fit the scene on the window, click on the left area of the applet and, then, press the “f” key. 
SUPPLEMENTARY INFORMATION

ORTHOGONAL PROJECTIONS, DESCRIPTIVE GEOMETRY, CANNONS AND FORTRESSES  
Descriptive geometry is the branch of geometry which allows the representation of threedimensional objects in two dimensions, by using a specific set of procedures. The resulting techniques are important for engineering, architecture, design and in art. The theoretical basis for descriptive geometry is provided by the orthogonal projections. Illustration: orthogonal projections of a car model. Gaspard Monge is usually considered the "father of descriptive geometry". He first developed his techniques to solve geometric problems in 1765 while working as a draftsman for military fortifications The French mathematician Gaspard Monge (17461818) is considered the founder of descriptive geometry. He used it in military engineering (construction of fortifications) during the time of Napoleon Bonaparte. In fact, descriptive geometry was considered a military secret. Dennis Lieu and Sheryl Sorby, in their excellent book Visualization, Modeling, and Graphics for Engineering Design, present the historical context:


Responsible:
Humberto José Bortolossi.
Idealization and Programming: João Júlio Dias Bastos Queiroz e Humberto José Bortolossi. Revision: João Júlio Dias Bastos Queiroz e Humberto José Bortolossi. English version: Carlos Eduardo Castaño Ferreira and Igor Bromonschenkel Brandão. Graphical library: JavaView – Interactive 3D Geometry and Visualization. 