"Follow Me" extrusion on a quarter circle does not look right


I try to create a quite simple structure, an L-shaped pipe, with a ninety degrees angle. I start with a ring that I pull out a bit, then I place a quarter circle path along the axis I want to follow it. The result is kind of going into the right direction but the resulting angle is not ninety degrees and all looks messed up. I need a push into the right direction to make this become a nice 90 degrees shape…


I think a few things can be said about this, but I suppose my first concern is that I’d be careful about where the path gets located. Placing the path as it’s shown here builds in distortions—in part because the far side of the cylinder has the longer arc to follow.

Keeping everything the same, what happens if you were to center the path along the center point of the circle?

…Distortions still exists, but you’ve now halved that by running the path down the center line.

Sometimes it’s better to over shoot the rotation you want to make. Then go back in, and trim back to the desired angle, afterwards. (… A cutting solid can be paired with Solid Tools ‘Subtract’ command… or, a cutting plane can be used with the ‘Intersect Faces’ command).

Also, having a little bit of ‘lead in’ (…and lead out for that matter) produces better results then just going straight into the curve… If that makes sense. Thus that bit where you started off by pulling up,… could be better placed as part of the path… as a straight lead in section going into the 90º curve.

[… kept in for context,… But, Box has provided a solution and correction to my following comments.]

On a different point of discussion,… because SketchUp uses straight line segments to draw all of it’s curves, and arcs with. It’s worth keeping in mind how the segment count divides into the angle that’s being used. Just to ensure that there are always full line segments in place… so that you’re not coming out of a turn which happens to end midway on a line segment. … see @Box correction, and Solution below:

SketchUp’s default settings here divide into 90º well, so this isn’t really a concern unless you’re changing these settings around.

The result…

Someone may have a one step operation here, in terms of a perfect 90º follow me turn. But, so far I’ve resigned myself to this being a multi-step process. where trimming back seems to be the easiest workaround.

Interestingly enough, if you look at the adjustment which happens between the offset tools preview vs. it’s placement results, you can see how there’s a little bit of ‘trim’, or ‘extension’ which comes into play at the end to true up the 90.

While I haven’t measure the angle (in the preview phase), it’s pretty close to the discrepancy that the follow me tool has.

But of course the follow me tool isn’t showing any post adjustments being made. Not that this is proof of anything. Or if it is then the explanation is beyond what my understanding is.

My guess is that this is primarily a consequence of how SU handles it’s curves, via straight line segments.

This is exactly what you do want to happen, because the follow me will be perpendicular to the half line segment.
By rotating the Path circle by half a segment you get a 90 deg follow.


I Love it Box, That is GREAT!!

I always thought of the end points segments as being more true to the real circumference. and thus more likely to be tangent.

But of course, as has happened many times before, a genuine SketchUp Sage steps in to clear things up.

(I’ll go back and strike out my misleading comments above.)

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