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Hello, for a project I needed to find the shortest way between two points in a network, so I searched for a pathfinding algorithm in AutoLISP. Since I did not find anything - here comes my implementation of the A* pathfinding algorithm. (If you don't know what A* is - I got my information here: http://en.wikipedia.org/wiki/A*_search_algorithm) The program finds the shortest way in a network of polylines between two points, the polylines representing the paths you are allowed to move along. Two polylines are considered connected if one of their vertices match. The resulting path is returned as a new polyline. The program and a test.dwg are attached to this post. I would like to extent the network/edges in a way, that polylines are also considered connected if the vertice of one of them is on the line of another. I could use some help with that. I hope this is useful for someone. astar_01.lsp test_01.dwg

I updated the code above to a new "radio button multi.lsp" it allows any number of buttons without hard coding. I will add the default button as soon as I get time as it an extra variable in the defun.

You could try this Program from @Lee Mac http://www.lee-mac.com/offsetpolysection.html Or this one http://www.lee-mac.com/doubleoffset.html

I thought the ease of drawing accurately was one of the benefits of using a computer aided drafting program. If you don't want accuracy, use a pencil.

Accuracy is paramount in the world of design. Anyone who tells you otherwise should be doing something else. A defect in a measuring device used to polish the mirror for the $1.5 billion Hubbell telescope made it virtually useless. It took a second mission (and additional monies) to fix the problem.

It's been my experience that, once an error creeps in, it will get carried through everything that connects with it. An architect will use fractional units and believe that getting within 1/4" is close enough. In other words, he'd never see a difference as large as .12. After a few more near misses, each one amplifying the ones before, he'd wonder why his stuff wasn't lining up properly. As SLW210 says, there's no excuse for doing it wrong when you have the tools to do it right. The people who will use your drawings are expected to work within certain tolerances. You owe it to them, and everyone else, to do the same.

It's too easy to draw it accurate and correct to accept anything less. Like rkent, I see no reason to sketch with AutoCAD. I fix any and all drawings I get or come across with inaccurate CAD work, if I am to work in them, if someone just wants something printed, I rarely bother to check it over for such things unless it just doesn't look right. Like steven-g, I find some programs convert poorly to dwg.

I probably spend half my time making other peoples drawings accurate, I have to take off quantities from drawings supplied by others, and it is so much easier to do that if polylines are closed and not made up of overlapping objects, it's a fairly simple formula to find the length and width of a wall given perimeter and area, but only if that information is accurate. For a 160 apartment tower block, it can take me nearly a week to clean up the drawings and get things on sensible layers. It is then just a question of days to take off the quantities and create the schedules, doing all that normally is 3 to 4 weeks. And by far the best drawings, in general, come from the structural engineers, that's just a question of checking for odd errors. Drawings from Architects, that's just hoping that you can find a few that are straight. I think many of the errors are due to how "other" programs are converted to dwg.

Your listed as CIVIL so with GPS setouts, 3d machine control accuracy is becoming more important. Its so easy to do it correct using snap and ortho to say it does not matter is not the sign of a good designer.

To me it is actually easier and quicker to do things accurately, and it looks so much nicer. From the stand point of getting something like a sidewalk built it probably doesn't matter, but I can't bring myself to "sketch" with CAD.