How to roll a surface from a corner?

Replies to This Discussion

Permalink Reply by David Rutten on December 24, 2015 at 2:39am

So the tip of the surface moves along a line that is coincident with the surface?

Permalink Reply by Vahid on December 24, 2015 at 2:56am

excactly

Permalink Reply by David Rutten on December 24, 2015 at 3:01am

That'll involve some pretty hefty trig equations. You'll need to be able to extend the bending arc beyond 180 degrees (which is not possible with the file I just posted).

Here's the problem as I can work out:

You need to create the correct arc (the thick purple curve), where 'correct' is defined as

|ST| = |SE| + |EX|

or, in English, the length of the line from the bending start S to the tip of the paper T, must be equal to the sum of the length of the arc (from start S to end E) and the length of the tangent line segment from the end of the arc E to the intersection X.

Then and only then will the tip of the paper be coincident with the paper itself after bending.

Thus, given X and T, equations are needed that describe S and either E, or the radius r and the angle α.

Permalink Reply by David Rutten on December 24, 2015 at 3:16am

Actually I think even in with these constraints there's an infinite number of solutions to that problem. You can vary the radius of the bending arc as long as the position of S moves accordingly. So an additional constant is required to pick only a single solution out of that bundle.

Permalink Reply by Vahid on December 24, 2015 at 5:00am

thanks a lot for your complete explanation, as you mentioned i tried to modify my arc with some additional parameters and i came up with a some how convective result, but since im very new on GH i think there should be a better way to control the X point as well.

Again thanks a lot for your time 

Permalink Reply by David Rutten on December 24, 2015 at 2:57am

The attached file allows control over the position and curvature of the bend deformation.

Attachments:

• BendDeform.gh, 6 KB

Permalink Reply by Vahid on December 24, 2015 at 3:10am

Thanks a lot, i didnt expect you to be such quick 

thanks a lot

Permalink Reply by Vahid on December 24, 2015 at 3:36am

not exactly what i wanted, i got the whole thing, but i think the definition for the arc is a bit too simple.  you have used expression : -X  i dont know why and how can i chage it to get my desired arc.

Permalink Reply by David Rutten on December 24, 2015 at 4:50am

The -x expression is just to flip the tangent vector. The arc goes 'backwards' from the point of view of the line, so I need to reverse the arc tangent.

You can make a more complicated arc if you want (one that doesn't have a horizontal tangent at the end), there's plenty of Arc components. If however you want to switch to a freeform curve rather than an arc then you cannot use the Bend deform component, that one only understands arcs.

Permalink Reply by Ola Jaensson on December 25, 2015 at 4:33pm

I'd use the Kangaroo plugin for that, and simulate the stiffness of the paper as hinged strips, to get the desired curve.

Permalink Reply by Vahid on December 27, 2015 at 3:34am

Thanks a lot