How to delete edges or faces?

Replies to This Discussion

Permalink Reply by David Rutten on July 12, 2015 at 4:20am

If a polyline edge goes through a triangle, then the result is no longer correct, that's why I divided the polyline edges to insert additional points.

Attachments:

• constrained_delaunay.gh, 7 KB

Permalink Reply by andy on July 12, 2015 at 5:40am

Hy again,

is there any way to not divide polylines (keep mesh simple), thi is done with delaunay mesh, is there 

maybe way to do this with delaunay edges (to delete those outer edges-lines)?

Here i attached file with those to objects (note the lines are exploded).

Thanks.

Attachments:

• question.3dm, 34 KB

Permalink Reply by David Rutten on July 12, 2015 at 6:34am

What actual problem are you trying to solve? Are you trying to turn each closed loop of roof edges into a single surface or mesh? 

Permalink Reply by andy on July 12, 2015 at 7:10am

Let's say yes if i understand question.

see image below.

Permalink Reply by David Rutten on July 12, 2015 at 8:51am

Ok, well I don't think delaunay is a good approach then, although you may end up using it anyway as your roof loops are not planar. If they were you could use the Rhino Planar Surface command or the Boundary Surfaces component.

The problem you have is that you need a constrained delaunay triangulation and Grasshopper doesn't have such an algorithm. Using vanilla delaunay means your mesh edges may not match up with your roof edges.

Additional problem is that if the curves aren't joined into closed outlines there's no way to determine whether a triangle is inside or outside a single roof.

Permalink Reply by David Rutten on July 12, 2015 at 9:00am

This is the best I can come up with without custom scripting.

It requires some manual pre-processing. All the roof edges have to be projected to a plane below all the geometry. Then you need to use the Rhino CurveBoolean command to generate all roof outlines. This can be done with a single click for all roofs, so it's not too bad a limitation.

Attachments:

• CreateRoofs.gh, 15 KB

Permalink Reply by andy on July 12, 2015 at 12:27pm

It is ok like that, but again one problem it has, that is that are every edge is divided by one point as i can see, right?

Does it have to be like that or it has solution?

Thanks for answering.

Permalink Reply by andy on July 13, 2015 at 12:12pm

Sorry for bothering again, take a look at this problem.

Attachments:

• question2.3dm, 104 KB
• CreateRoofs_2.gh, 14 KB

Permalink Reply by David Rutten on July 13, 2015 at 4:43pm

Yup, I said:

All the roof edges have to be projected to a plane below all the geometry.

Permalink Reply by David Rutten on July 13, 2015 at 4:42pm

Without a constrained Delaunay algorithm it has to be like that. In fact you may even need more than one edge division depending on the input geometry.

The meshing behaviour you are after is not very delaunay-like, so you may have to switch to a different algorithm, but that means either a plug-in, or a lot of custom coding.

Permalink Reply by andy on July 14, 2015 at 9:25am

Yes delaunay mesh is not good solution. Let's close this thread.