In an e-mail, Adrian suggested that the two main criteria are:
I installed Varkon on my SuSE 9.1 Linux system. The source may be downloaded here.
Following these instructions I compiled the program to a directory in my home directory. Adding four environment variables to .bashrc and commenting out three in the makefile were required. With that accomplished, make ran to completion without errors and the program starts by typing "varkon &" at a shell prompt.
The above mentioned tutorial dates from 1998 and refers to varkon_1.15C. The version I installed is varkon_1.18A. 1.15C apparently came with a sample project named projekt_1. It is not present in 1.18A, but there are other demo projects available here.
A description of the "Demo applications" begins just a short way down the page, with links to instructions and pictures for each demo. Have patience, and scroll to almost the bottom of the page to download demoApp.tar.gz to get them all. Unpack it in the varkon directory in your home directory and it will put files in the appropriate sub directories, app and pid.
The README file associated with the demo says to look at the job bike1. A bicycle appears in its own window. Next they say to try clicking buttons. The first button they recommend is help. Nothing happens. Then they suggest trying Edit-P on the frame or a wheel. This does allow the editing of the parameters for a wheel. The rear wheel has 60 spokes, and the front wheel has 20. Changing the number of spokes parameter on the front wheel from 20 to 60 produces a change to the drawing causing the front wheel to look like the rear wheel, as expected.
Clicking on list in the menu window shows that bike1 is made up of 1 instance of a frame, 2 instances of a wheel, and 80 instances of a spoke. A handlebar appears in the drawing, but not in the list.
The next recommendation is to create my own bike2 job. No mention of how to do this is made, but I guessed right that one first exits the open project, then restarts varkon, selects bike, and types bike2 in the text input box. A drawing window does appear.
The user interface is not particularly robust. If you try to start an action that won't work in the current state, there does not appear to be a way to cancel that action short of killing the process. Clicking on the "close" x in the title bar of the window has no effect, either on the drawing window or the menu window. Right clicking on the button for each of these windows and clicking close also has no effect.
While doodling about with the program I discovered that the way to get back to the main menu is to click on white space on the drawing window.
When Varkon starts, its windows are placed along the left side of the screen. This places them on top of desktop icons. Several times I've clicked on something in one of the Varkon menus and found an unexpected window opening. Upon inspection, these windows turned out to be the result of clicking on the icon under the Varkon menu. It's not clear why the menus appear to be transparent with regards to the rest of the desktop, but moving them over a bit to the right eliminated the problem.
Picking up again on David MacMillan's 1998 tutorial, I drew a line. Of course, I tried to do things that Varkon didn't like, and had to kill the program and start over.
David gives step by step instructions that cover almost every keystroke and mouse move. Unfortunately, that's "almost" and not "every" move. I got to the point of entering the starting line coordinates, typed 0 in the X coordinate box, and then hit
I followed David's directions through step 5 of his section 4, Project Setup. All worked as described. I started in on section 5, Coordinate Systems, but the code he provided did not compile, nor was I successful in figuring out why.
I did go back and look at the other sample projects that came with the group in which Bike was included. These showed a number of the features, but didn't really give much instruction on how or why to use them. In at least one case, the Fighters demo, the README file instructs one to "Try the "shade"-button in the toolbar to see the shaded image." There is no "shade" button. Experimentation eventually showed me that the effect they describe is achieved via a button labeled, "Dyn-R" which is short for Dynamic Rendering.
Perhaps a programmer would appreciate this CAD tool, since much of the work is done by typing in code. With time and patience, I suspect I could figure it out, but while I usually have plenty of the latter, I'm a bit short on the former. Also, I'm used to a more traditional CAD program, having started with Generic CAD back in the 1980's on an old PC-XT! So, for now, I'll set Varkon aside and have a look as some of the other tools.