bool union fail of two lofted surfaces

Hi all!

I´ve some troubles with the bool union operation. I´m trying to create a hull for a tower with a kind of a long narrow slot in the middle. I used the loft method for two sets of section curves which created two closed Brep. Next Step should be the bool union of the two surfaces, but the Brep union component returns null. I also tried to make Meshes out of the Breps but the result is what you see in the image.

left: the two loft surfaces; right: the mesh union result

here are the files:

tower%20test.3dm

loft%20tower%20test.ghx

does anybody have some ideas/suggestions?

does anybody know another way as the loft method to define the hull?

many thanks,

Christoph

Replies to This Discussion

Permalink Reply by David Rutten on July 1, 2011 at 8:08am

The problem is the Rhino4 intersector/boolean solver. If I run this in Rhino5 it works well for Breps but not meshes.

David Rutten

david@mcneel.com

Poprad, Slovakia

Permalink Reply by Christoph Degendorfer on July 2, 2011 at 1:24am

hm, ok thank you very much for the reply/testing the files...

I´ll try to work this out in Rhino 5, or thinking of another way to generate the hull.

If anybody have a suggestion to another way of defining a hull with holes, I would appreciate every hint!

thanks

Permalink Reply by Christoph Degendorfer on July 2, 2011 at 1:41am

I tried the mesh relaxation like in this thread:

http://www.grasshopper3d.com/forum/topics/how-to-create-nodesbone?c...

the created form is kind of tight, of course, but also inflating the mesh (spring lenght larger then original) doesnt deliver a smooth surface.

Permalink Reply by Daniel Piker on July 2, 2011 at 2:17am

Can you post the file, or at least an image ?

Permalink Reply by Christoph Degendorfer on July 2, 2011 at 3:41am

sorry...

here are the files

left: spring lenght <1

right: spring lenght >1

so as I mentioned the aim is to create a hull with a hole

1. try: Loft a set of curves (problem is the loft method work just for one section curve after another, if there is a kind of a crotch(?) I have to do it seperately for each Volume and bool it later, with the Problems at the top of the thread

2. try: out of a rough mesh structure and then mesh relaxation. Problem is to inflate the mesh

no more ideas...

thank you for your help

Attachments:

inflate tower hull.3dm, 196 KB
inflate mesh.ghx, 382 KB

Permalink Reply by Daniel Piker on July 2, 2011 at 4:42am

Making the edges springs with rest lengths longer than their start lengths is different from inflation, and will normally just result in the mesh crumpling up, as you found.

Inflation (internal pressure, like blowing up a balloon) has its own component in Kangaroo, acting on the 3 points of each triangle in the mesh. For this you will need a triangular mesh. Using WeaverBird's Loop Subdivision instead of Catmull-Clark will give you this. For a smoother surface you may also want to use a higher level of subdivision (or subdivide again after inflating in Kangaroo, to speed things up).

Also, using a cleaner starting mesh will give better results. When you union Breps and mesh the result, the meshing will be messy and asymmetric, which will affect the result of the subdivision and inflation. Building a mesh from scratch allows more control over this. This thread might help:

http://www.grasshopper3d.com/forum/topics/how-to-create-nodesbone

Alternatively - use T-Splines - it's made for exactly this sort of thing.

Permalink Reply by Daniel Piker on July 2, 2011 at 5:36am

Here's an example of how to use WeaverBird and Kangaroo to subdivide and inflate a tube with holes.

Attachments: