Multi-point arc

[eldon]

This raises another question; how do I make an equation-driven spline? I made this polyline using Excel, can I use the same method to make a spline?

 

I am not familiar with any technique except feeding in the coordinates in succession after the initial command SPLINE instead of PLINE.

[SEANT]

Now I guess I want to "flatten the spline" so that I can fit a certain # of arcs along the length of the spline. The flatten command posts on this forum talk about thinning out 3D objects. I'm guessing the flattening SEANT meant was picking, in your case 8, points along the spline, then using the flatten function to extend those points into arcs. Is this correct? How do I do this, seeing as how I want ~36 arcs along the length of the spline?

 

It just so happens that this parabola decomposition task requires a bizarre assortment of AutoCAD commands that were not necessarily named in accordance with all the functions they perform. The Flatten command, for instance, was named for the primary task of flattening 3d objects, but will also convert a spline (planar or non-planar) to a multi-arc facsimile.

 

 

As for SEANT's .dwg, thanks. How can I change from the Start/End/Center to a Start/End/Radius? The radius would just be to some constant arbitrary point.

 

With regard to transferring the Excel data to a spline; I’d follow eldon’s suggestion to initiate the Spline command (instead of Polyline) when performing the fuccaro technique.

 

Alternatively, the spline I had included in the .DWG file is a pure representation of that parabola (compare selected points on the spline and compare it to the excel returns). The problem is that the Flatten command, unless some additional parameter exists, will only produce an eight arc facsimile. Even with only eight, though, the resolution looks pretty good.

 

For what its worth (and because AutoCAD Tables are a bit of an unknown) here is an Excel version with the inclusion of radii. I’ll leave any reformatting to you.

RadiiTable.zip

[JD Mather]

I am not familiar with any technique except feeding in the coordinates in succession after the initial command SPLINE instead of PLINE.

 

I don't think I would type in coordinates. I'm sure there are plenty of lisp routines available to create points from Excel data. (I used to have one when I still used AutoCAD.) Then snap Nodes. Probably routines to create splines directly (I use Inventor which does this automatically).

[PhysicsCAD]

Ok so I think I have the methodology down. I am going to try JD Mather's technique as soon as Express Tools gets installed. Hopefully I can explode that into 36 arcs. I will also try to explode SEANT's flattened spline into 36. I'll keep you posted.

[eldon]

I don't think I would type in coordinates. I'm sure there are plenty of lisp routines available to create points from Excel data. (I used to have one when I still used AutoCAD.) Then snap Nodes. Probably routines to create splines directly (I use Inventor which does this automatically).

 

I did not type all the coordinates in, too much chance of mis-typing. I copied and pasted into the command line. No Lisp involved. Those of us without Inventor have to make the best of it.

[PhysicsCAD]

Okay I finally managed to use the explode command and converted the parabola into 10 segments. When I click properties, it displays these segments as "Line". When you create a 3-point arc does it display as a line in properties? Also, JD Mather said there is a way to control the # of segments you can explode the selected spline into, does anyone know that command? Again, thanks for all the assistance in helping me create this curve.

[JD Mather]

Okay I finally managed to use the explode command and converted the parabola into 10 segments. When I click properties, it displays these segments as "Line".

 

You should be getting arcs - not lines when you run Flatten and then Explode on a Spline. Something isn't right. Attach what you have before you run the Flatten and Explode commands.

[PhysicsCAD]

Here is the curve so far. I flattened it then exploded it globally this time (by selecting both sides, press ENTER then G). It looks like ~28 arcs, but it's hard to be sure. Now I just need to make them arcs with Radii values and put them into a table. Hopefully I can figure out how to fix the "arc resolution" problem and set it to 36.

spline para.dwg

[PhysicsCAD]

Here is the curve BEFORE using flatten and explode. Try to explode it individually (you get 10 lines), then globally (~28).

spline para before.dwg

[JD Mather]

It looks like ~28 arcs, but it's hard to be sure. Now I just need to make them arcs with Radii values and put them into a table. Hopefully I can figure out how to fix the "arc resolution" problem and set it to 36.

 

Window select all of the geometry and then type LI and hit Enter.

The List window should tell you how many arcs you have and their information.

 

For the life of me I can't recall how to control the number of arcs that are created.