topic Drawing an Arc Length in Modeling

Drawing an Arc Length

Anonymous — Tue, 24 Aug 2004 15:58:03 GMT

Is there any way to draw a precise Arc length using Archicad?

I am working from a surveyor's drawing, and need to input the arc length with a given radius.

(I think I know the answer is "no" or "buy an add-on" but I am posing the question so I can ask the next question: Why not? )

Re: Drawing an Arc Length

Anonymous — Tue, 24 Aug 2004 16:31:47 GMT

Not to my knowledge, the only way I have found is to dimension the arc and adjust it as you can to get the length. If anyone else has a trick, I'd also be happy to hear it.

As for the second question : I have no idea.

Re: Drawing an Arc Length

Erika Epstein — Tue, 24 Aug 2004 18:28:31 GMT

Other than calculating it geometrically,

You could try opening the
Element Information window/palette under
Windows,
Floating Palettes.
Draw the arc with the given radius. In the Element Information window chose the "last Selection" radio button. This will give you the length of the arc you drew and then you can 'stretch' the arch like stretching a wall (cmd/ctrl H) and then type in the difference to stretch the arc to the specific length you want.

Note it doesn't give you the radius, just the angle but if you know the radius you have enough information to accomplish what you want.

Re: Drawing an Arc Length

Jacek — Tue, 24 Aug 2004 18:37:14 GMT

Erika wrote:
Other than calculating it geometrically,

You could try opening the
Element Information window/palette under
Windows,
Floating Palettes.
Draw the arc with the given radius. In the Element Information

Erika, great Tip!
I have almost forgatten about this feature! Used it a while ago and since forgot about this 'little gem' - Thank you.

Great tip...

Anonymous — Tue, 24 Aug 2004 19:30:54 GMT

Hey Erika,

I really like the info palette, but i still don't get to PRECISELY input an arc length. If the info palette was interactive, now how cool would that be?

Or am I not understanding how to use it properly?

Re: Drawing an Arc Length

Erika Epstein — Tue, 24 Aug 2004 19:44:02 GMT

To input the distance once you have done cmd/ctr H type in "r" and the the distance. In this instance 'r' refers to the length you are adding/subtracting to the arc, NOT the radius.

Yes, it would be nice if it were interactive. As I am a stickler for precision, I would still be entering the exact dimension, not eyeballing it.

Re: Drawing an Arc Length

Seiss Wagner — Wed, 25 Aug 2004 16:34:46 GMT

Finding the length of an arc (circumference) is of interest, but of limited value. A much more interesting and useful question is how do you draw an arc knowning the cord length and radius without resorting to geometry?

Re: Drawing an Arc Length

Jacek — Wed, 25 Aug 2004 17:40:19 GMT

Seiss wrote:
,,,, A much more interesting and useful question is how do you draw an arc knowning the cord length and radius without resorting to geometry?

Hmmm... would you not be able to generate an arc by using the third elipse tool; establish your radious (r=?), then input your cord length (x=?), and complete your arc?

Re: Drawing an Arc Length

Jacek — Wed, 25 Aug 2004 17:43:21 GMT

Seiss wrote:
,,,, A much more interesting and useful question is how do you draw an arc knowning the cord length and radius without resorting to geometry?

Hmmm... would you not be able to generate an arc by using the third elipse tool; establish your radious (r=?), then input your cord length (x=?), and complete your arc?

By the way, where are you going?

Re: Drawing an Arc Length

Seiss Wagner — Wed, 25 Aug 2004 19:20:43 GMT

By the way, where are you going?

Jacek - I am going dyslexic by way of the way of the "radious".

I don't think the third elipse tool would work. I have tried various strategies with the three point circle tool, with no success.

Re: Drawing an Arc Length

Stephen Dolbee — Wed, 25 Aug 2004 19:38:09 GMT

Any arc I have drawn (from a survey) has been in tangent with a line or another arc. I just go 90 degrees from the endpoint to find the center of the radius.

Steve

Re: Drawing an Arc Length

Jacek — Wed, 25 Aug 2004 20:40:48 GMT

"Seiss Wagner" wrote:
I have tried various strategies with the three point circle tool, with no success.[/quote

and Steve wrote: "I just go 90 degrees from the endpoint to find the center of the radius. "

-That's the way I do it

Re: Drawing an Arc Length

Seiss Wagner — Thu, 26 Aug 2004 05:31:57 GMT

Steve or Jacek

I don't follow how you go 90 degrees from the end point to find the center of the radius. Can you give my dim mind a screen shot of what you are doing to get a surveoir's arc.

Seiss

Re: Drawing an Arc Length

Stephen Dolbee — Thu, 26 Aug 2004 12:26:59 GMT

Seiss wrote:
Steve or Jacek

I don't follow how you go 90 degrees from the end point to find the center of the radius

This example might be a little simplistic, but here it is. Hope it helps.

Steve

Re: Drawing an Arc Length

Seiss Wagner — Thu, 26 Aug 2004 17:04:45 GMT

Steve -

Thanks much for the screen shot, it really helped. Which Arc/Circle tool are you using? If I use the Three Point Tool I can draw the cord, constrain 90 degrees with the perpendicular icon, but then I must pull the diameter of the arc to get the radius. Is that how you do it?

Seiss

Re: Drawing an Arc Length

Erika Epstein — Thu, 26 Aug 2004 17:29:13 GMT

Another method is to draw a circle of the known radius at each end of the chord. Where the two circles intersect is the center of the arc you are looking for.

Re: Drawing an Arc Length

Stephen Dolbee — Thu, 26 Aug 2004 17:48:28 GMT

Seiss,
I use the center point circle.

Steve

Re: Drawing an Arc Length

Seiss Wagner — Sun, 29 Aug 2004 06:11:33 GMT

After further investigation, I have found the three point circle tool does not work for a chord arc as I had previously posted. It only seems to work if the radius is large. The three point circle tool will work for a chord arc if you bisect the chord and and graphiclly input the chord rise which equals r-½ the square root of (4r²-c²). But this is more effort then either Stephen's or Erika's posts.

So I guess it is back to drawing circles. ':('

Re: Drawing an Arc Length

fuzzytnth3 — Tue, 07 Sep 2004 08:31:04 GMT

Seiss wrote:
Finding the length of an arc (circumference) is of interest, but of limited value. A much more interesting and useful question is how do you draw an arc knowning the cord length and radius without resorting to geometry?

I made a library object that does this. I've attached it below. We found it very useful when setting out a multiple curved building.

Enjoy

ARC TOOL.ZIP ROCKS THE HOUSE!!!!

Anonymous — Tue, 07 Sep 2004 14:00:08 GMT

The character in Scotland made a goodie!

This deserves praise for cleverness, though curses to Archicad for needing it.

Put this one on the Tips and tricks board!