Wish: Arc from start, end, origin

[Rhino_Bulgaria (Bobi)]

I believe that Rhino lacks one very important feature which is creating an arc from start point, end point and then the origin (distance from the middle between the start and end points to the tip of the arc). This could be very useful for mechanical and architectural projects where the goal is to create shapes with a specific height (or depth) between two points. The Command line could include an additional option to set the direction of the arc. This could be automated for the RMB version of the command.

Arc from start, end, origin.3dm (132.9 KB)

A similar case was mentioned in this topic:

How to connect 2 lines at a certain height without using a third line

Hello everyone. Today in class, the teacher gave us an assignment. Let’s try to connect 2 red lines with height d = 0.5, but without using the green curve. I did some research and found out that there is a script (paid) that can do this. However, is there any tool on RHINO that can do this quickly? Please help me. Thanks. File.3dm (106.2 KB) [QA_1]

[3dsynergy]

Hi @Rhino_Bulgaria

Yes this would be a welcome addition.
Hope McNeel implements it.
Thanks for posting this
RM

[Helvetosaur]

Made a script for that quite awhile ago. Almost forgot I had it.

ArcStartEndDepth.py (2.1 KB)

[Rhino_Bulgaria (Bobi)]

I just tried it and it’s great! Thanks!
It projects to the active Cplane, which is not optimal (requres to set a new Cplane before running the script).

If possible, can you make an alternative version which also asks for the direction of the arc before setting the depth? That way, the user could set the direction and snap to some object located in a random location (not planar to the active CPlane).

[Gijs (Gijs de Zwart)]

would you need it always as a symmetrical height based on end points (right), or as in the case left in this image as well?

[Rhino_Bulgaria (Bobi)]

Ideally, the tool could offer both options. I can see usage of both, primarily in architectural projects where the ground is inclined (as in your left side image). Perhaps that will require to set a direction for the height (the “h” vector) and a reference point (bottom of the “h” vector) that could be any random point other than the start and end points of the arc itself.

[davidcockey]

@Gijs

would you need it always as a symmetrical height based on end points (right), or as in the case left in this image as well?

The right case, height measured from the line between the end points, is the one I would use.

[Gijs (Gijs de Zwart)]

I’ve logged that case to start with. I think the other case is more rare and would become a convoluted UI anyways.

RH-89561 Arc startpoint, endpoint, height/direction

[jeremy5 (Jeremy)]

@Gijs

I think the other case is more rare and would become a convoluted UI anyways.

In the meantime, it isn’t a difficult construction with Rhino’s existing tools:

1. Offset the baseline by h with the gumball
2. Arc, tangent to curves, pick start point, end point, offset line.
3. Delete offset.

[Helvetosaur]

@Rhino_Bulgaria

It projects to the active Cplane, which is not optimal (requres to set a new Cplane before running the script).

If possible, can you make an alternative version which also asks for the direction of the arc before setting the depth? That way, the user could set the direction and snap to some object located in a random location (not planar to the active CPlane).

You can try this one… Added an extra point pick to determine arc plane, or hit Enter to use active CPlane.

ArcStartEndDepthPLus.py (3.2 KB)