So this isn’t really a “problem,” but I was curious as to how CC generates toolpaths. I’m engraving a road map into some plywood with a v-bit. The outcome is looking great, however, as I’m watching it carve, it seems to make the most inefficient movements. What causes it to bounce all over the place instead of simply finishing an area and then moving on to somewhere else. For example, there are some letters that are getting v-carved within the map. “Roseberry Creek” is the text. I’m 1 hour into the job, and it’s been back to the letters a total of 5 times. The DOC is .05, which is less than the tool’s capability. What prevents it from simply finishing the letters before moving on to other parts of the project? The roads portion is extra crazy. It’s just making laps around the project over and over, even though it could cut the full depth of the entire road in one pass. Thoughts?
This is an NP-complete computer science/logic problem, “The Traveling Salesman” — it’s not possible to have an algorithm which will always calculate an optimal solution in a reasonable amount of time.
Although TSP is NP complete, there are many heuristics that have very reasonable running times that would beat the pants off whatever algorithm CC is using today.
It’s not actually clear that CC is actually using an algorithm in the classic CS sense - it seems that it’s mostly “run through these paths in whatever order they happen to be represented internally” rather than an actual ‘choice’ of order being made. See, for example:
I’ve recognized patterns in the V-Carve / Advanced V-Carve process…
It seems to be something like:
Create regions based on ‘bi-tangencies’ (areas where the tool can contact 2 vectors at a time.
Create regions based on intersections of ‘bi-tangent’ areas. [ex: the center of a Y or X]
Cut the intersections first
Then cut the ‘bi-tangent’ regions
Then come back & pick out any ‘corners’ (any non-smooth vertex) or section of a vector that has a curvature smaller than the radius of the tool.
And in each of these processes it seems to move next to the closest start point of any region that hasn’t been cut. So some times it will make several cuts in what we would think of as a region, but then jumps to the next region because the start point of that cut is closer.
What I haven’t figured out is the “Move all the way across the job & start over there” part. ??
Unless that’s just the next closest start point before moving to the next step??
It is quite painful to watch. But the thing is, many of the very expensive CAM software can not do this at all. (or very easily without a lot of interaction).
One thing that would be really nice is a toggle to turn off the “picking”, i.e. walking up the sharper corners. I have many jobs that look great before that step, and it does waste a lot of time. There are some corners that have as many as 7 little ‘picks’ before moving on to the next cut.
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