Measure Curve Length

Swizl

Well-known member
#1
Measure Curve Length

Ok, so when modifying a straight spline into a curved line, the length changes. I need to maintain the length of the spline instead of distorting it when changing the curvature. I'm dealing with modeling sign inserts (usually paper or flexible acrylic). So being able to measure the spline curve would be really helpful for me to maintain a constant length while bending the part. The ruler tool will only measure from a straight point to point.

Not sure how viable this may be for Martin to do, but this is the wish list section!

:)
 

frank beckmann

Well-known member
#2
You lost me here completely.
You´re constantly posting files started as AI-files and now that your beloved vector app isn´t able to display the length of curved Bézier curves you want Cheetah3d to step into the breach? Absolutely no offense intended but don´t you think it´s about time switching to another vector.app? :p As I said: "No offense!"
Just curiosity. ;)
BeziersLength.png

Cheers
Frank
 
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Swizl

Well-known member
#3
Well the problem isn't just measuring a static line length, but an animated one. I'm still in the process of finishing the animation you helped me with a few weeks ago that uses point animation. This time it's the paper that I'm working on and it's a lot less rigid than the acrylic clear lens. These aren't elastic parts, so warping of the part is unrealistic. I could possibly created steps of the spline and import and use as a sort of blueprint for each step. Kind of like stop motion animation. I'm not an illustrator fanboy, I'm a FreeHand guy, but they killed that one off. Not that FreeHand could measure a line length anyway. I don't have any problem using another vector app in all honesty though. Anything that gets me to my goal. The spline in this case was 100% created in C3d. Either way it doesn't matter what it's origin is.

Which app did you use to measure those path lengths? Is that InkScape? Usually I do pull vector art into C3d because a) I'm faster drawing in a vector app and b) sometimes I get line art from our engineers for extrusions that I import.

No offense taken! I know this is more in the SolidWorks / Maya / 3D Studio Max territory. But it would still be useful to me and this is the "wish" section after all.
 

frank beckmann

Well-known member
#4
Yeah - it´s Inkscape. (and Freehand-user since 1989 till Adobe annexed Macromedia.)
Maybe one of the script-gurus is able to write a script about it: Spline with labeled length. ;)

Cheers
Frank
 

Swizl

Well-known member
#5
Ah ok, I do have InkScape installed. I just found out that the Get Info palette in Illustrator will give the length of a line even if it is curved. I will post over in the Scripting section to see if any of the many talented script writers we have here are interested.

A few other methods I may use are to use an UV map with equal squares on them. They possibly may show when I'm going past my target O.D. width. Even using the dotted line you just replied to in another of my posts could help. As long as the dashes stay the same length, I could just count how many are showing and compare that to the amount when the line is straight.

Thanks for the replies. I'll get this accomplished one way or another. It will just take some trial and error.

:)
 
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Shift Studio

Well-known member
#6
Hi all.

Any updates on this topic?
I have a some sweep creators where the guide path is all curled up in many 3D directions. Now I have to straighten it out and keep the same length:oops::eek:

I can think of some very tedious methods, but I really would like to avoid them. I don't think measuring in Inkscape is an option for me as the spline is not 2D.

Thanks, in advance!
--shift studio.
 

Swizl

Well-known member
#7
Hi all.

Any updates on this topic?
I have a some sweep creators where the guide path is all curled up in many 3D directions. Now I have to straighten it out and keep the same length:oops::eek:

I can think of some very tedious methods, but I really would like to avoid them. I don't think measuring in Inkscape is an option for me as the spline is not 2D.

Thanks, in advance!
--shift studio.
Hi all.

Any updates on this topic?
I have a some sweep creators where the guide path is all curled up in many 3D directions. Now I have to straighten it out and keep the same length:oops::eek:

I can think of some very tedious methods, but I really would like to avoid them. I don't think measuring in Inkscape is an option for me as the spline is not 2D.

Thanks, in advance!
--shift studio.
Hi Shift, I'm not aware of any other work arounds or scripts that have been added since this discussion. Someone else may have come across another fix though that I've haven't seen. Hopefully so, because it would be really useful.
 

Swizl

Well-known member
#9
@Swizl Yes it would be very useful (actually I've never needed it before, but really need it now ;) )
If I come up with a good solution I'll post it.

--shift studio.
Some of the tools in C4d have a checkbox for it. There's also a way to do it in Blender, but I can't seem to export from C4d and get a spline (curve in Blender parlance) and import it into Blender.

If you can get a spline (curve) into Blender 2.8, there is a method I found online that you can enter this code into the console with the curve selected and it will output the length in the console. I changed the Timeline into the Python Console, but you can change any window you want.

bpy.context.object.data.splines.active.calc_length()

There must be an equivalent mathematic JavaScript formula that could be use most likely in C3d, but I'm not smart enough to pull that off. :D
 

frank beckmann

Well-known member
#11
I have an idea:
1. Pick your spline and a Plane of a given Width+Depth and put it into the Chain-creator (Alignment set to: mix)
2. Now add so many Links: to it till the planes touches slightly each-other.
3. Read out the number of links and multiply the given size of the Plane - result is the length of the spline: the length is 121 units in this case.
SplineLength.jpeg


Cheers
Frank
 

Joel

Active member
#16
I’m not a mathematician, but I can still appreciate an “elegant solution.” C3D is a playground for people who love geometry, and Frank has a supernatural ability to recognize patterns and create processes. A wonder to behold.
 

Jeanny

Active member
#19
Thanks !
BUT if you have a parametric rect. Spline you don´t need this method, right?
That is a good Question ?:giggle:
I don't need it then.:giggle:

Do I have it right for a Circle? :unsure:
I was just trying to duplicate what you did with the rectangle using a circle instead.
I think I'm starting to get it but I need to comprehend exactly what is happening better.
I need to spend some more time going over this thread to fully understand it when I'm not so tired.

I would like to use this method to measure the circumference of some some organic cylinder type objects I'm working on.

:) Jeanny
 

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