Find Closest Point/s On Closed Surface

Hi All

After trying over 24hrs of trying to crack a code i have run out of workflows so asking here...

Does anyone have any ideas on how to find the closest point/s on a closed surface from a defined point on that surface. I have a working code for an open surface but yet to find a way to rebuild the logic so it work on a closed surface.

In the attached the code the surface is reparameterized surface but this is only beacuse the test is using an MD Slider

Thank

Matt

Attachments:

closest point on open surface by UV.ghx, 91 KB

Replies to This Discussion

Permalink Reply by robert cervellione on January 16, 2011 at 8:12am

the component Brep CP does not work for what you need

Permalink Reply by Giulio Piacentino on January 16, 2011 at 8:27am

Does it have to be by UV?

This example is by distance.

- Giulio

Attachments:

closestpointonopensurfacebyDist.ghx, 137 KB

Permalink Reply by Dedackelzucht on January 16, 2011 at 8:28am

mh, post a surface example. the only possible solution I can imagine is an orthongonal (to the suface) point situation.

Permalink Reply by Matt Gaydon on January 16, 2011 at 9:03am

Hi Robert, Guilio and Dedacklzucht

The Brep closest point will not work as i am seaching for points all ready on the surface created using Srf Divide and seaching from a defined point on the surface.

The reason i was using UV as the standard closest point code and your attachment looks though the surface no around it to define distance between points.

Here's a pic of the problem on a basic torususing UV Point data to calcualte distance from point

And Below is using point dat to calculate the distance and as you can see it looks though the surface not around it

Thanks

Matt

Permalink Reply by Giulio Piacentino on January 16, 2011 at 9:13am

(from the example above)

Permalink Reply by Matt Gaydon on January 16, 2011 at 9:18am

I had tested the example above you posted, but it failed if the distance though the surface is short than the distance of points to seach for. as in the example pic i justed added to my reply. I wish it where what simple :)

Permalink Reply by Giulio Piacentino on January 16, 2011 at 9:38am

Sorry, I do not understand. Maybe can you be a bit more specific about what you are looking for? Are you looking for the 8 points that surround a point on a surface? (like in N, NE, E, SE, S, SW, W, NW?)

Permalink Reply by Matt Gaydon on January 16, 2011 at 9:48am

Sorry it for a larger Paneling Script, at present i was just trying to calculate the distance to every panel on the surface from a single point (the single point defining in the entrance to the space). With this distance data i can tell GH which type of panel to pick from the types created in T-Splines and map onto the given panel. The panelling is a bit special though as it designed to overlap at certain corners. I havn't posted this as did not want to confuse and this problem when sovled could be used on on other projects.

I am trying to work out also how to push points on the surface using the data gained from this script too (distance/vector etc) but first need to sort this out.

Thanks Again

Matt

Permalink Reply by Giulio Piacentino on January 16, 2011 at 10:08am

I think I understand. Maybe you could use the geodesic distance?

Also, keep in mind that when dividing a closed surface, at the seam there will be double points.

Attachments:

closestpointonopensurfacebyGeodesic.ghx, 140 KB

Permalink Reply by Matt Gaydon on January 16, 2011 at 10:25am

I had looked at Geodesic Distance before i started on the first code idea i posted, this still has problems with the seams as can not gap them to find a close point on the otherside.

Thanks for the note about the double points i had forgot to remove them from the current example code, though the panelling does not have this problem.

Permalink Reply by Giulio Piacentino on January 16, 2011 at 11:03am

It should be able to jump over seams...

So let's have an overview of what we have so far. Can you tell which feature is missing?

	method 1: UV distance	method 2: euclidean	method 3: geodesic
seams	stops at them	jumps	jumps
meaning	on-surface distance in surface coordinates	aerial distance in world coordinates	on-surface distance in world coordinates
note	not good because of seams behavior	not good because it can capture points in other areas	it is restricted to local areas

Permalink Reply by Matt Gaydon on January 16, 2011 at 11:45am

Seems overlooked that Geodesic Component seems to have some bugs in Rhino V5, Including jumping seams....Sorry.. Works ok in rhino 4 even if I input all 200 panel centres.

Thanks for all your help. If i think of a quicker computational way than Geodesic as it seems rather heavy i will post it here.

Matt