CIRCLE Tan Tan Pt - behaving unexpectedly

This was working as expected when the trimmed surface was created with a pipe. For some reason, it is not able to track the edge curve when the surfaces is lofted, which makes no sense.
When I bake the curves and build the circle in Rhino, the result is as expected.


What did I miss?


I tried rebuilding the curves but that didnt help

CircleTT_2020May05 (10.8 KB)

It works for me (R6, Win10):

I can drag the reference point to get the other result:

yes, but this is no longer achievable: R6 Win10


This is the desired result… a much larger radius circle tangent to the two curves, no matter where the point is positioned.

In GH, the tangents only occur at the end of the curves (and may not be tangent)

They look tangent to me in both cases.

Maybe you need to demonstrate how you achieved the larger circle that doesn’t touch the curve endpoints?

By the way, if the curves are not co-planar the circle will be tangent to only one of them.

I simply ran the command in Rhino. I moved the point in the x direction to achieve the desired radius.
Something odd is happening and I suspect it has to do with the Cplane. As you move the point around to update GH, there is no movement of the tangent curves untilo they suddenly snap to the other end of the curve.
This behavior is not present when the circle is built in Rhino, and was not the result when I used a Pipe in GH
So, i gues the next step is to create an example with the pipe that behaves as desired and then switch to loft and find the difference.

Neither of these curves is coplaner, but that didnt seem to both the method before. I got a perfect tangent on both curves and a circle of the desired diameter. So I will work on a demo to show this…

The mirrored ‘Planar Curve’ is indeed co-planar with its source curve.

Many things affect GH results including curve direction, plane orientation, etc. You can go crazy trying to make sense of it all. Better to focus on what you want and how to get it, then move on!

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I have put the two processes side by side using the same line and point. The curves are coplanar in this example to eliminate that.


CircleTT PIPE 2020May05 (13.0 KB)

I dont get it.

I would like to use the lofted surface. It doesnt fragment like the pipe when trimmed.

The edge curves that you are mirroring are different lengths and going the opposite direction, as you can see by examining their start points, Also, the one you labeled “CORRECT” has this error message on the CircleTT component:

  1. Circle could not be fit in one attempt

You can get a nearly identical result from the Loft by using Flip Curve on the edge before Mirror and adjusting the two sliders ‘Angle’ and ‘Degrees’ to match the edge curve from the sliced Pipe:

CircleTT (19.4 KB)

Thank you for identifying the curve flip issue.
(This specific example is also an exercise in debugging for me)
Adjusting the sliders to move the end of the curve where the tangent is being made removes the needed surface lower down unfortunately, so I will have to trim the extracted curve.

The direction of the circle is dependant upon the direction of the underlying curve it seems. It tries to match to the nearest part of the curve, which I dont want.

If that is removed, it matches to the part of the curve that is available resulting in the desired result.

Thank you again

Well this appears to be about curves, not surfaces.
I am still not able to get the desired result even when I trim the curve at the apex.
I dont understand why one curve creates the desired circle and the other doesnt.

20-05-06 CircleTT PIPE (9.0 KB)

2020-05-06 17_24_14-Window

In Rhino, both result in the desired result:


Well I moved on to Circle TAN TAN TAN PT which behaves more predictably. Without a better description of these components or a manual, its hard to know how they are doing what they are doing.