sweep question

Hi yall
Is there a way to use the sweep 2 rail command in GH, to keep one of the rails constant and to keep the section length constant?
thanks for the help and for this beautiful program...

Replies to This Discussion

Permalink Reply by Vicente Soler on August 17, 2009 at 11:00am

There's a boolean switch on the sweep2 component for keeping the height constant. What do you mean by keeping one of the rails constant?

Permalink Reply by Thomas on August 17, 2009 at 11:11am

Hi Vicente
thanks for the quick reply. I have tried the boolean switch and I thought that would make it, but it doesn't seem to work quite the way i want it. What i'm trying to generate is a metal louver that waves up or down according to external parameters. The problem i have with the sweep2 right now is that the external edge waves the way i want it, but the section change because it matches the constant distance between the planes containing the two edges. I would like to keep the internal edge horizontal and planar, and the external edge to wave in all axes to keep the section constant. the problem is that the curves i'm using are both planars, and one of the directions is constrained by this fact. (hopefully i made myself clearer but my answer is so long that i'm not sure anymore...)

Permalink Reply by Vicente Soler on August 17, 2009 at 11:16am

An image is worth more than 148 words. I think it will be beter understood if you post a screenshot or file.

Permalink Reply by Thomas on August 17, 2009 at 11:22am

That's exactly what I was thinking after my last post. Hopefully this will help:

Attachments:

sweep problem.jpg, 581 KB

Permalink Reply by Vicente Soler on August 17, 2009 at 11:38am

I'm still a bit lost, but from what i understand in this sentence:
"The problem i have with the sweep2 right now is that the external edge waves the way i want it, but the section change because it matches the constant distance between the planes containing the two edges."
Maybe you could divide each sweep into two different sweeps that sort of mirror each other. And divide the cross-section into two pieces. Then mantain one of the sweeps constant, while the other varies along the external edge.

You could also post a correct version modeled manually in rhino to see exactly what you are after.

Permalink Reply by Thomas on August 17, 2009 at 12:16pm

I've found a way to model it, but it's a completely different method. i know the command exists in rhino, but I will have to redo everything completely if I have to use this. So if you know a way to work it around you will save me a lot of time...

Attachments:

twist.jpg, 979 KB
difference.jpg, 187 KB

Permalink Reply by Vicente Soler on August 17, 2009 at 1:17pm

You can create many sections made out of straight lines, rotate them individually and loft them together to produce a sort of twist:

* Click on the image to make it bigger.

Permalink Reply by Thomas on August 17, 2009 at 1:34pm

mmm I think i need to update my grasshopper version since mine doesn't look like yours. Is the box with the logo on it a heigtfield from bitmap kind of command? If it's as simple as it looks, you made my day i think. Do you think you would be kind enough to give me the gh file (I think i can replicate though, but if you give to me it will save me the effort :))...
The only think that is not similar to my original goal is the not constant interior edge. Other than that you have a definition that is exactly what i'm after...

Permalink Reply by Vicente Soler on August 17, 2009 at 1:44pm

oops, i didn't save the file. I think the only missing data from the screenshot is some of the image sampler settings. You have to change both intervals from "0 to 1" to "0 to 50" and set the output as the brightness value. The PI constant has a 0.5 multiplier.

If you want the interior edge to be a straight line delete the length curve component and connect directly the points to the plane's origin input.

If it looks different maybe it's because I've enabled 'draw icons' under the view menu.

Permalink Reply by Thomas on August 18, 2009 at 2:41am

Vicente
I cannot find what the box with the image is (on your definition capture screen).
Could you help me out one last time with that?

Thanks a lot.

Thomas

Permalink Reply by Vicente Soler on August 18, 2009 at 2:50am

Have you downloaded the latest release?
You can find it here: http://www.grasshopper3d.com/page/next-build
The component is called 'image sampler'.

Permalink Reply by Thomas on August 18, 2009 at 7:15am

I didn't see that, thanks a lot. Too bad because I just had to write a shitty definition myself to do the exact same thing based on a heightfield surface. It took me a week :( (i'm not too skilled yet).
Anyway, thanks a lot for your help vicente.