Mini CAD Design Help

Question

Hello I would first like to say that I am not a professional programmer. My degree is in electronic engineering and I work at a steel fabrication shop. My function at the shop is designing automated tooling. Because of my love for C++ and C# I frequently get programming projects thrown my way. The apps I mostly develop are utilities that we use in the office. Because I don't work on a team of developers and that I am not a computer science major I feel like my development efforts lack the proper design needed up front to yield strong software. Having said that is why I am asking for your help. I need to develop a simple CAD type app that will allow the user to create and edit a simple 2d parts to be produced on a CNC machine. I know you are thinking why don't you use AutoCAD or any other package that all ready exist? The answer is I have thought of doing a VBA app for AutoCAD but I feel that this should be simple enough why tie up an AutoCAD license when we just need to draw a few circles and rectangles. What I was thinking of is creating some type of a custom class that would define the entities: For example: Circle Class Rectangle Class Line Class ETC. these classes will contain xy values for the end points as well as methods on how to draw each entity on the screen. How do you select a entities from the screen so that they may be edited..etc? What about a dimension that could reference two other entities? I may be way off base on this thing if that is the case pleas let me know as well as any better approaches! Please guide me through this design I am ready to learn!!! Mike

Mahesh Chand · Answer

Yes! So what you need is on mouse down (left or right whichever you choose) if your mouse is on top of a shape rectangle for example you need to select it means draw another rectangle that looks like it is selected. In selected state if you mouse move you need to move the shape (redraw in otherwords) and once mouse move is done drop it and unselect it. To merge two shapes you can use union intersect options. This needs to be done using Geomerty objects in WPF. In GDI+ it used to be done using Path and Regions where you could merge (union intersect etc). You can also create a Geomerty object in WPF and add multiple objects to it and then draw it that is what you will see merging objects on front end. I will post a link to Geometry objects articles soon. I worked with them couple of years ago and need to find out my documents :).

Sam Hobbs · Answer

Mahesh your articles look like good introductions to drawing. Do any of them show drawing of objects that can be modified and moved as objects? In other words if a rectangle is drawn can it be dragged (moved) elsewhere and can it be resized? Can another rectangle be added to it and then both rectangles be treated as objects?

Mahesh Chand · Answer

I built a Firefox kind of application using GDI+ and C# in year 2000. That is when I wrote the GDI+ book. But now with WPF it is even more simpler. So there are two ways you can build this product. First Windows Forms (GDI+) and second WPF. I would recommend WPF. Go to WPF section and learn how to work with various shapes and select them and move them. This site has lot of articles and tutorials on this. Here are some ideas: PaintBrush in C# PaintBrush in C# - II Drawing Shapes in WPF Shaped Windows in WPF G ood luck!

Mike Sportman · Answer

Thanks for the advise Sam. It is very interesting that you are associated with so many machinist. I worked in a machine shop during my college years to earn money I developed a passion for machine work there. My father-in-law was also a machinist and kept a photo of a piece he had built in the top of his tool box. He told me it was a part for a rocket ( it would have had to of been an Apollo rocket ). I did not hear the news about the bridge demolition project but that does sound impressive. I agree with what you are saying and to finish a project of that magnitude before the estimated schedule WOW! Your are correct in assuming the products a relatively simple. Once again thank you for you support!!!

Sam Hobbs · Answer

My father was a machinist. He claims to have run the machines that built part of the Space Shuttle. My brother and brother-in-law are machinists. I know they do CNC programming but they are not programmers. Unfortunately I cannot help much. I know the obvious; that you will need at least two big pieces graphics and database. I think you are headed the right direction by designing your system to use entities/objects. You should learn graphics programming such that you can manipulate items in a drawing as entities/objects. You should look for books that help with that. I assume that your products are relatively simple. In large products perhaps as large as automobiles or airplanes there might be complex hierarchies of items whereby assemblies have components that are assemblies. Designing a database that can manage a hierarchy such as that is important. Hierarchies are common; a computer's file system has folders and sub-folders. If your products/drawings are simple then the heirarchy won't be a problem (hopefully). When I was at Lockheed I talked with the group working on the newer CAD/CAM; I think they called it Edge. I assume you are familiar with CADAM one of the original CAD software. One of the design goals of the newer sofware was the ability for the Engineers to design aircraft that was as close as possible to what can actually be built. At that time the Engineer would design something but the aircraft had to go through a major redesign to be buildable. If you want to be able to provide something like that then that might require an important amount of designing. In other words do you want the Engineer to be able to design something and then get the CNC programming out? If so then the software might need a special level for figuring out how to make something. Perhaps it needs to know about tools material and manufacturing instructions. You might want to also think of Order Location and Project Management systems. I can't help much beyond telling you what you already know. I think the one thing I can say to help is that it helps to design it. You need to analyze the requirements; think about the things I described above. Decide what you need to do. Analyze it as an Engineer; don't try to decide how to build it. Decide what you need first. Being a non-programmer helps with that. Did you hear about Carmageddon in Los Angeles this past weekend? They de-constructed half a bridge but only half a bridge lengthwise. They did it in about 35 hours ahead of scheduloe. They did not blow it up; it was a very precise Engineering project. As an Engineer you understand the need for planning. That applies to software too; it will help to be methodical in the design.