Inkscape is a vector graphics application that has many tools and features found in expensive commercial applications. It's often used by those who want to avoid unnecessary expense to produce their documents. Though Inkscape is a two-dimensional application, you can use its tools to create the illusion that a graphic is 3-D. For example, if you want to make a 3-D cube in Inkscape, the process is quick and easy.
Start the Inkscape application.
Go to the toolbar on the left and select the "Create 3-D Boxes" tool. Drag with the tool to draw a cube onto the canvas. Don't worry if it's not exactly how you want it.
Switch to the "Selection" tool and drag the arrows that appear around the cube to make it exactly the size and shape you want. Save your work.