Grasshopper

algorithmic modeling for Rhino

How to choose grid points lying inside a surface?

Hello :)

I have been having difficulties figuring how to choose points that lie inside a surface to which I applied grid points (DivideSurface). I do not really know how to deselect points that are located on the outline of the surface. 

I am real beginner and I am aware this is the basic knowleadge but still... :( 

I would really appreciate any help :)

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You have three approaches that may work:

  1. Convert the surface edge to a curve, then measure the distance from all your points to this curve. Those points with a very small distance are on the edge. This is handy because it does not depend on well-ordered points, or even untrimmed surfaces.
  2. Project your points to the surface UV space, and find the ones that are along the edges of the UV domain. Although this would mathematically be the most rigorous approach, I think it is by far the most complicated.
  3. If your points are well ordered (in separate columns, in ascending order), then you can remove points logically. Ie. remove the first and last column entirely, and also remove the first and last point of each remaining column.

I think #1 is the most intuitive and flexible solution.

Thanks for your reply. 

1) Tried doesn't work. What I did was: I pluged into A of the Distance component my surface's edges, into B all the points of the grid. Panel says that all the values equal <null>

2) I have no idea how to do this one.

3) My points are pretty well ordered, but there are only 4 of them. They all create a surface. All the other points of the grid were added after I used command Divide Surface. Again I do not have any control over them because I didn't create them one by one.

I upload a screen shot so it might be easier to understand what I mean. :)

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I now have points on the outline chosen but cannot substract them from all of the grid points so they wouln't be a centre of an circle anymore  . Basically what I tend to achieve is to get circles only inside the surface, not on the outline. 

I tried merging the start and end points of the curves and substracting them from  all the grid points using mathematical substraction. It didn't work the way I hoped.  

Thanks in advance :)

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Hope this is helpful.

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Yes,exactly what I was trying to do. Thank you so much :)

Thank you! This is just what I was looking for

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