## Solve a problem and make a problem

Thursday, July 31st, 2014 at 10:05 am

We’re having some classic Austrian weather right now. It’s been rodding it down since 5am. I’ve been eating Egg And Chips enough times for it to lose its special status.

Most everyone else is caving at the minute. I haven’t seen Becka in 5 days. I’m waiting for better flying weather.

This is a great time to get some work done on these pesky stay-down linking in the Adaptive algorithm.

Here is an example of the A-star linking path calculated in its setting of the rest of the cutting toolpaths, so you can see how it fits in. The path must traverse through the area without colliding with material that hasn’t been cut yet. This image is of the first iteration. There’s a secondary process which pulls the path of light blue dots tight within its structural matrix once it is connecting in the right direction.

What I mean by the right direction is the way that the path rolls off the preceding path and rolls on to the next cutting path. I can calculate the shortest path reliably now, but it would sometimes result in going 180 degrees back on itself if it’s shorter to go round the circle, so the trick is to artificially insert a circle of exclusion that it has to avoid as it finds its shortest trajectory.

This worked well most of the time, except that the path would sometimes go the wrong way round the circle. It doesn’t know any better. It just finds the shortest path which it can. So I inserted this radial blocking line to block off paths that started off the wrong direction.

And of course sometimes the radial line becomes a liability and the stupid shortest path thing has to go all the way around it when it should be coming in to the path nice and smoothly. I just worked this one out this morning.

It takes ages to discover these errors in the data, looking at unusual tool motions in real examples, and trying to separate them out into the debug development environment so they can be analysed and plotted.

In computational geometry, if you can’t see it, you can’t debug it. In the real world you’d hope that a corporation that depended on vast quantities of computational geometry would have a dedicated team helping programmers visualize their messed up algorithms, so they don’t have to hack up crazy things like my “webgl canvas”.

I’ll spend the rest of the day getting to the root of this one, I guess, and then be one insignificant step closer to finally getting this out of the way.

I don’t deserve to enjoy any flying until I do. Nor do I deserve another egg and chips.