Meerkat GIS Street Offset - trim/cull intersecting curves

Hello,

I am reading curves from a SHP file using Meerkat in Grasshopper. The curves are placed where streets are placed. I have offset in both the positive and negative direction in order to get correct width of the street.

My question is how do I remove the intersecting curves. My first thought was to use a pattern cull and then reference the base street curve as the culling pattern, and then the remainder of the curves as the list component.

Red: base curve

Green: offset curves

Is there an easier way to accomplish this?

Thank you,

Forrest Walker Whitmore

Attachments:

Intersecting_Curves.JPG, 62 KB

Replies to This Discussion

Permalink Reply by nikos tzar on September 3, 2014 at 6:20am

Here is an approach:

Find the intersections between all the curves, break[shatter] each curve at its intersection points and remove all segments with small length.

This is far from a perfect solution, as it will not work when streets are very close to each other (it will cull lines you actually need). But since you haven't provided your file I could only test it with a few street lines I created in GH.

you can check it with your file and see if it helps.

good luck,

nikos

Attachments:

streets.gh, 15 KB

Permalink Reply by Forrest Walker Whitmore on September 3, 2014 at 8:52am

Thank you for the help Nikos. I had the previous steps in my definition except for the culling of a specific length. I wasn't sure how to specify what was to be culled. I didn't upload my file because of it's excessive large file size. I will test what you have created and see how it acts with my street curves.

Thanks again,

Forrest Walker Whitmore

Update: I receive an error with the Shatter component "1. Solution exception:Object reference not set to an instance of an object."

Permalink Reply by nikos tzar on September 3, 2014 at 9:37am

Hi Forrest,

I don't know why you could be getting that error. My guess would be a data matching problem. Can you check that the two inputs of [shatter] have exactly the same data structure?

On another note, I thought of a way to make the definition more effective:

before culling the curves based on their length you could cull all the curves that intersect with the street axis so you can then use an even lower number for the length-based-cull and have less chances of removing a useful curve:

Yet you'll have to solve the error with the shutter component first.

If you can find a way to post your files it will make it easier to get help with this one.

good luck,

nikos

Attachments:

streets.gh, 18 KB

Permalink Reply by Arend on September 3, 2014 at 8:44am

You might give the offset method of clipper a try. It can handle an offset of multiple curves without problems.

http://www.food4rhino.com/project/clipper

Permalink Reply by Forrest Walker Whitmore on September 3, 2014 at 9:02am

The plug-in page says that it doesn't support curves? How does it work with trimming extents?

Permalink Reply by nikos tzar on September 3, 2014 at 9:49am

ok, just checked it with a bunch of curves in clipper and it works like a charm! No need to use my complicated definition. It is very intuitive and it seems to work with curves also, so imo that's the way to go.

Amazing job there Arend, thank you for this plugin!

edit: only problem now seems to be offsetting each curve with a different number.

if I apply 4 curves and 4 numbers(both as simple lists-not trees) it offsets each curve with all the numbers. And when I graft both inputs it offsets each curve on its own (as expected). Maybe Arend can help with this one....

Permalink Reply by Forrest Walker Whitmore on September 3, 2014 at 12:31pm

Hi Nikos,

Can you send me an image of how you set up the Clipper component with your test curves?

Update: I forgot to unblock the files within the Grasshopper folder. That works perfectly! Thank you both very much for your help!

Permalink Reply by Arend on September 3, 2014 at 2:06pm

hi nikos, if you want that you should graft your curves. two lists will not work, because the offset component accepts a lists of curves (which can be nice, because you can offset a network of loose curves, instead of each one individually).

Permalink Reply by nikos tzar on September 4, 2014 at 6:06am

Hi Arend,

I did some tests and this is what I get:

1.No Graft:

2. Graft curves:

3. Graft both:

So it is not possible to offset a network of curves, each with a different distance, right? (only each curve individually)

Do you think that could be possible in a future release (if you plan on making one, that is)?

Thanks again,

nikos

Permalink Reply by Arend on September 6, 2014 at 3:26am

Hi Nikos, if I do that, it will be adding a feature to do a boolean/region join the curves at the end.

It's very easy for you to do that:

Use a trim component, to strip the last 2 path indices (or use a path mapper), and use the region union command to join all curves together.

Permalink Reply by nikos tzar on September 6, 2014 at 5:23am

you are right... (i feel a little stupid now)

Thanks again!

Permalink Reply by Arend on September 3, 2014 at 2:07pm

it works with curves, but they're treated as polylines. so if you have e.g. an arc, it will be segmented. should not be a problem with the geometry shown.