Getting points on imported 3d curve

acheever

Getting points on imported 3d curve

in Contributed Library Questions • 1 year ago

I want to import a 3d curve and get internal points on it, such as points equally spaced along the curve. In 2d this works real well with the Geomerative library and importing SVG fles. In 3d, I'm at a loss. I am thinking Objloader library bringing in NURBS in a obj file, but how do I get access to the points on the curve?

Background: I'm using Processing to talk to Wiring which drives an Arduino which drives stepper motors on a custom CNC machine. The first step was to have Processing read 2d vector art in the form of SVG file and have the motors follow the curve at a prescribed resolution of straight line segments, like a very simple GCode. The next would be to follow a 3d curve in the same way but I don't know how. Maybe I need to find a way to generate Gcode and read that into Processing?

Any help would be really appreciated!

Replies(6)

allesblin..

Re: Getting points on imported 3d curve

1 year ago

In 3D your complexity will increase by a dimension. My suggestion would be to import a triangle mesh (like OBL or STL) and try to develop a contouring algorithm, that calculates your tool path for the CNC machine. There are numerous strategies you can use for this, like slicing your object into discrete layers or spiraling upwards around your geometry.

A good starting point for this is Paul Bourkes Contouring algorithm: http://paulbourke.net/papers/conrec/

Also search for "tool path generation" and "CAM"

acheever

Re: Getting points on imported 3d curve

1 year ago

Thanks! Contouring a surface was going to be my more advanced problem to solve next. I want to do something simpler. I just want to import a 3D curve (NURB, Bezier, etc.). Then display that curve on the screen, and put an ellipse on equally spaced points on the curve, like every 5% of the curve length. In 2D, this can be done with Geomerative functions. But in 3D, there must be a way to get points on the curve.

I believe if I actually drew the curve in Processing, then I can get intermittent points with the curvePoint function. I want to do the same, but with an imported curve.

allesblin..

Re: Getting points on imported 3d curve

1 year ago

Ah, now I fully understand your question. Your assumption is true. bezier curves and quadric curves also work in 3D. Which 3d program are you using? All the importers I have seen so far do not care about NURBS or curves. Just about vertices, edges, faces.

acheever

Re: Getting points on imported 3d curve

1 year ago

Hmm, I guess importing the actual 3D curve is the first step. I just assumed that ObjLoader did that too. But if it only imports vertices, then I guess I can use those to create curves in Processing and then use the curvePoints function to get inner points. I guess I just need to control the end tangencies somehow. I did see the iGeo library but didn't dig into it yet. Thanks for the help.