subsurface extraction

hi, first of all, pardon for my bad english.Im a grasshopper newbie and hope u guys can help me out with my problem.

I have an issue with extracting a subsurface from an untrimmed surface basically I wanted to create a definition by inputting a surface and then GH will simply create a window frame based on that input surface.

[I have attached my definition and a screenshot for you guys to have a look.]

I added a slider to control the dimension for the frame. I dont wanna use the "offset crv on Srf" approach, because that component seems to be sending the definition to rhino and then convert it back to GH.

so I decided to use subsurface extraction to get the untrimmed surface which then I can feed it to another definition.

the problem is that because the Srf needs to be reparameterized, I cant control the frame dimension. I added simple math definition ( Frame width/Crv Length in U direction ) to translate the frame dimension to fit within number 0.0 to 1.0

the problem is that if the surface is trapezium, the frame width will slightly change on one side of the surface. ( because of how UV works )

is there any way to solve this problem?? any help would be appreciated.

thank you guys....

Attachments:

help guys.PNG, 153 KB
help me guys.gh, 5 KB

Replies to This Discussion

Permalink Reply by Pieter Segeren on January 10, 2015 at 5:53am

Hi Runnie,
I think your english is pretty good, and I think what you want is this:

Attachments:

AltSubSrfs_PSG.gh, 20 KB

Permalink Reply by Pieter Segeren on January 10, 2015 at 6:16am

Doh! Just noticed you wrote: "I dont wanna use the "offset crv on Srf" approach", but I don't follow your reason for that.

Permalink Reply by Riccardo Majewski on January 10, 2015 at 6:27am

Fast and short method, Pieter.

But using "edge surface" component will create a new surface that probably will not have the same shape of the original.

Try this.

3 methods to get internal curves to create the frame.

Method 1: "fast"(maybe) but often imprecise and incomplete.

Create a series of circles, itersect them to the surface to get point to interpolate internal curves to trim final frame.

Method 2: the unwanted!

Using offset on surface component.

Method 3: piping

It seems that "pipe" component doesn't "spam" in rhino UI as offset on surface does, will this be ok?

Intersecting pipes to original surface to get internal curves.

Permalink Reply by Runnie on January 10, 2015 at 11:04am

@ Pieter Segeren. = thanks for the reply mate. I dont wanna use offset crv on Srf because the component uses Rhino command to get it to work. and when I need to adjust the slider, or feed it to a more complex definition, it is going to be very slow. I will be using this definition to aid me during my modelling process. later I will feed it to anothe definition to generate the internal frame.

anyway, I really appreciate your time to help me think about this matter. thanks mate :)

@ Riccardo majewski = Hi mate, using Pipe to get a fixed dimension sounds great, but the problem is that the surface output is always a trimmed surface. it is always be a problem for a trimmed surface to be used as another input for more complex definition.

however, I quite like your idea mate. thanks for being so helpful guys :))))))))))))

Permalink Reply by Riccardo Majewski on January 10, 2015 at 12:31pm

Ok, I'll fix that when I'm back home.... no prob

Permalink Reply by Runnie on January 10, 2015 at 1:17pm

okay, thanks mate. :) Ill wait for you then :)

Permalink Reply by Riccardo Majewski on January 10, 2015 at 6:13pm

This should be good, but it's hard to explain.

Inside the 4-sided frame I extracted some U and V nurbs curves to create a final network surface that copy enough well the original shape.

Check if this is good, and tell if you need the correction to work with many surfaces at time; at the moment, just 1 surface at time.

(Its already heavy, maybe multiple "parallel" application would be a pain anyway...)

cya

Maje

Attachments:

grasshopper_nurbs_frame_v2.gh, 33 KB

Permalink Reply by Runnie on January 10, 2015 at 10:11pm

hi mate, seems like u are using newer version of GH or u installed some plug ins that I dont have. the network surface component is that a plug in or it is already embedded inside GH latest vers?

can u attach your screenshot as well?

thanks buddy

Permalink Reply by Riccardo Majewski on January 11, 2015 at 4:48am

Network surface is a normal grasshopper component, no plugin needed.

It shouldn't be a new/fresh component, there should be present also in older versions of grasshopper.

I've marked the last part of the definition, see pic.

tell if you still have problems :D

Permalink Reply by Pieter Segeren on January 11, 2015 at 4:55am

Hi Runnie, Riccardo,
I chose to go the EdgeSrf way to avoid a trimmed surface, indeed it isn't the exactly same shape, but I figured it might be within your tolerance.
Thanks for pointing out that OffsetOnSurface is reflected in Rhino command history, I never noticed that (oh my)... Which commands do this, why is that, and what are the implications?
If you find having an untrimmed surface most important, wouldn't the calculation time be that much of an issue perhaps?
I'm anxious to find out what Riccardo is going to come up with! In the mean time I'll post my hybrid definition ~ (thanks Riccardo). It's got a whole lot of shifting paths and flipping going on, and several pitfall cases when it fail (i.e. when uv curve intersects border), but maybe you can edit some things to have it work in your situation.

Attachments: