Burrman,
I had looked at your post in which you included results from Rhino's UnrollSrf command.
(MoI's edge = 18.7470243394886 / Rhino's unrolled edge = 18.7500218509622) I guess I looked at that and decided it was close enough for me. But I don’t want to imply that I don’t appreciate people who strive for more precision.
In the model which I posted earlier, I used 15 points of correspondence: The results were:
38.1236928 for the edge of the solid and
38.1219458 for the curve derived by the Curve Through Points method.
In the next model using the same form, I simply increased the number of points of correspondence to 30:
The results were closer:
38.1236928 for the edge of the solid and
38.1235415 for the curve derived by the Curve Through Points method.
I also laid the first curve (derived from 15 points) over the second curve (derived from 30 points) and zoomed in close to examine to amount of divergence. I snapped a few lines from various points on one line to the other resulting in lengths of:
0.006009, 0.0005429, 0.0010549
I would assume that if one increased the number of points of correspondence towards infinity (a true curve) the length of the derived curve would approach the true length of the curved surface’s edge. That gets into calculus which makes my head hurt.
Those tools describing the relationship of length to radians to degrees are interesting. I will have to examine them when I get a chance. To be honest I never understood why there should be another way of measuring angles besides degrees. I dismissed radians without really trying to understand their practical use. Thanks
- Dan

Dan, Those results are close enough for me too. I will explore your post more later. I laid the curves length out flat as you did and my surfaces curve edge came out in the 20's. Way off.

Since yours came out so close, I will explore and digress to what you've done there.

Thanks for getting back to me.

By pointing out the difference in the Rhino edge and the original, really miniscule, I was just pointing out that it is not an exacting thing, from what I have read and tried to learn on it. Your results are great too. I was assuming since you laid your line straight as did I that your curve would be way off like mine. But NOOOoooo. Mucho gracias for the post!

Here's a script Michael put together that you can run while in any of the curve,arc or line commands that will show the length in realtime.


script: /* Show length of current curve being drawn */ try { moi.ui.commandUI.setInterval( 'var crvs = moi.geometryDatabase.getObjects().getCurves(); var len = 0.0; if ( crvs.length > 0 ) { len = crvs.item(crvs.length-1).getLength(); } if ( !window["_crvdistlabel"] ) { document.body.insertAdjacentHTML( "beforeEnd", "" ); } _crvdistlabel.innerText = len.toFixed(4);', 250 ); } catch(e) {}


Start any of the commands, like arc or freeform or line, and pick your first point. Then hit the script and a label displaying the length will appear in the active command window. I wanted to ask for this label to be an editable field (Click and change the value) like the other EditSize boxes and such, but it just didnt seem that prominent of a function. I can get it other way's. I would be the guy who puts 10,000 tools on the front end. :O