Smooth curve

Sorry if this has been beaten to death but…

I need to model the look of a record, 78, 45, 33.333 etc, for a laser engraved job. No matter how many segments, piecewise approximated circles create an unacceptable pattern as the endless end points align groove to groove and swirl. Human perception well suited to picking out the pattern. I had to create the spiral in SolidWorks and import it.

Is there an extension or other way to create smooth curves in SketchUp?

Short answer: No. Curves are always represented by short straight line segments in SketchUp. You can use shorter segments to make smoother looking curves but they will never be perfectly smooth as you are expecting.

As @DaveR noted, curves in SketchUp are made up of short lines. Just for fun, I created a 12" spiral with 50,000 edges. The segments were created at fixed angles, so they get shorter toward the middle of the spiral. spiral.skp (2.4 MB)

Nice moiré effect!

1 Like

Even on a 78 rpm 30 cm record the grooves are less than 0.5mm apart and on a LP they are about 0.15 mm. I wonder if a normal laser engraving machine can achieve that accuracy.
Why don’t you use real vinyl discs?
If you draw the grooves as concentric circles (forget about the spiralling) and export the result as 3D model to DXF, the engraving software ought to see the lines as circles, not segmented, and to be able to use its best resolution.

great points. For this I didn’t need to exactly model the pitch, just make it look like a record. Product is a Bluetooth player for Victrolas. When on the turntable looking like a 78 is a plus.

Issue is really the Laser. In vector mode the laser dwells at each segment endpoint which creates a divot. In raster mode the sweep creates ghost lines especially when groove is perpendicular to raster…diagonal not too bad. Possibly there is a Goldilocks pwr & speed setting??

Thought of using actual records but cutting even a little vinyl with a LASER is bad, voids warranty and damages lungs.

ahh! As a rookie not allowed to include pics that illustrate above.

Zoom the image (Ctrl +mouse wheel on a PC) and see moiré variants.

I did a smooth spiral in SolidWorks but what’s the challenge in that??

If I could randomize the # segments per spiral or the length of each segment the Moire should disappear.

Here is the endpoint dwell issue encountered in Vector mode. If the end and start points for segments overlap then the laser will spend 2x more time on that spot and hence the deeper dot which enhances the moire.

on this run I had manually changed the #segments every few spirals but didn’t totally fix.

As I wrote before, you won’t get away from the endpoints in the curves in SketchUp. They are a fact of life.

here’s a raster ghost line issue…
Screen Shot 2021-10-25 at 6.40.46 PM

Thoughts on randomizing??

I’ve never run across and extension that could do that. Might be something one of the Ruby wizards could do. If it’s possible you might be able to hire one of them to write it. Put a request in the Commercial and Collaboration category. You might get a bite.

Perfect, much appreciated. :wink:

Good luck.