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Arc helpers

Perhaps underlying this issue is that, originally, when I suggested Jon add a Bezier helper, I asked for the wrong thing. I gave this screenshot (my CYYJ)as an example of what the helper was to accomplish.

What I was looking for was a helper that would specify a series of linked curves and straight lines (for which I used the Bezier function in Gmax to create the lines in the picture).

I think you'll all agree that creating these lines with a series of arc helpers is hardly ideal.

Don
 

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With that kind of response from George, perhaps what we've got is good enough!

Don
 
Hi,

I quote Don:

What I was looking for was a helper that would specify a series of linked curves and straight lines (for which I used the Bezier function in Gmax to create the lines in the picture).

I think you'll all agree that creating these lines with a series of arc helpers is hardly ideal.

And cannot confirm what George says that it is easily done.
That is to say, I cannot do it easily:(.
 
What I am not sure is that a bezier helper will be any easier to use that an arc. Helpers are just that - to help or form the basis for a shape. The original idea was to allow users to copy a curve etc by placing vertices along the line. A series of helpers placed together should provide a framework.

What we seem to be heading towards is the ability to draw some more complex shape and then have ADE convert it to a series of vertices. What I would like to do is provide an easier way to match a curved target (whether it is based on a bezier or not is less relevant) with a helper. I think I might be able to do this with a cubic bezier (based on four points that the user can manipulate). Whether this will be much easier to use I don't know. Alternatively if the real goal is to be able to draw taxi junction curves for GPs then maybe I need to find a method that lets a user select a junction and get the vertex set from that?

Don I am not sure what the bezier function in GMax does - how do you define the shapes?

Perhaps a better idea of how these helpers might be used would help me?
 
Hi Jon,

I have no idea how Gmax works but in Sketchup it is like this:

suarc.jpg


I.e. you select the arc feature, draw a line and bend it the way you want with your mouse (it is not a Bezier curve just a combination of 5 arcs shaped with your mouse and it took exactly 30 seconds to make it).
Here is another one that took me 20 seconds:

suarc2.jpg



Roby
 
Last edited:
scruffyduck said:
What we seem to be heading towards is the ability to draw some more complex shape and then have ADE convert it to a series of vertices.
Click to expand...

The ultimate would be to allow a smooth curve, possibly with discontinuites, to pass through a series of points.

In the 70's, most CNC machines had only linear and circular interpolators. We devloped an interactive program to fit such curves and from them to create 3-D surfaces. We were able to achieve accuracies of 1mm over a length of 1000ft.

Of course, I no longer have the program ;)
 
How long did that take you, George?

The difference between the way it is done in SU and the helper shapes of ADE, is that the arc helpershape does not change the arc angle degrees but distorts the arc when you try to change it.

adehelpershapearc.jpg


Gee, it is hard to explain but I hope you see what I mean.

Roby
 
The ultimate would be to allow a smooth curve, possibly with discontinuites, to pass through a series of points.
Click to expand...

I could probably figure that out given enough time but................
 
Roby - you are correct - you are changing the major and minor axes of the arc. If you want to change the swept angle then that is currently edited.

The arc helper was always experimental and it is not pefect by any means. I think I can improve it but I am not sure when at the moment.
 
Morning Jon,

I can understand you lack the time to do it.
But if it were possible to edit the swept angle like you said with a handle and drag it with the mouse, I would be more than pleased.
 
robystar said:
Morning Jon,

I can understand you lack the time to do it.
But if it were possible to edit the swept angle like you said with a handle and drag it with the mouse, I would be more than pleased.
Click to expand...

Hi Roby

I will look at that as well but I am minded to find a better solution all together.
 
I understand how it is done, George. But how do you calculate the degree of arc between two points and/or the arc radius to get the correct curvature?
You have to admit it would make it a lot easier if you could reshape the swept angle of the arc without distorting it?
 
robystar said:
But how do you calculate the degree of arc between two points and/or the arc radius to get the correct curvature?
You have to admit it would make it a lot easier if you could reshape the swept angle of the arc without distorting it?
Click to expand...

I use guidlines to measure angles. I decide the radius by trial and error.

I don't understand what you mean by swept angle, the above shots show the same radius curve with two included angles, 65 and 120 degrees.

If you wish, you can create elliptical arcs by changing the axes values but I don't think this is very useful.
 
It might be better if the basis of the arc is a circle rather than an ellipse. I generalized it but I could easily change that.
 
What I like about the GP lines is that they "merge" when they become tangential :)

 
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