Differentiate Between Two Types of Creases on Grasshopper


Would anyone know a way of differentiating between two types of creases on Grasshopper?
In the picture below, you can see all the selected creases (Besides the Silhoutte Creases). But is there a way to differentiate between creases that appear to be a boundary (Or appear to be attached to on surface) from creases that appear to be attached to two surfaces?

Basically, I want to be able to choose the lines I have indicated below to define the distinct object in my Make2D.

I’m not sure. If the distinction is possible, it may be that I’m not outputting that information at this time.

Can you upload your data so we can be sure we’re talking about the same thing?

Render Test.3dm (1.7 MB)
Rhino Render Test.gh (36.4 KB)

I attached the files. What I am trying to get is something similar to the picture I have below. You can see that the thick outline defines each autonomous geometry rather than just a silhouette around a bunch of separate geometries. When I Boolean Union two geometries, you can see that the thick outline in the other image re-adapts to distinguish the combined geometry as one entity. Basically, from Make2D, I am trying to get the creases that appear to have only one surface attached to it in that Perspective View differentiated from the creases that appear to have two surfaces attached to it in that same View.

I only thought this could be possible since Pen Display view (From the images below) already does that trick for me, except I can’t extract those distinguished lines as vectors.

Hey David. Were you able you find if a distinction is possible? A silhouette per object basically is wat I’m trying to get to.

@rajaa @GregArden Looking at the code for the Make2D component, I can’t work out how to distinguish between these. What combination of silhouette types would yield the right distinction?

Any ideas? Apologies for my perseverance. @GregArden @rajaa Would this be possible to get the silhouette per object in the drawing instead of a single exterior silhouette for the entire geometry? The same way the pen display mode does?

Thank you,

Remember that I put this on the list as RH-49523 in your other thread about this. You can follow progress there. It’s on Rajaa’s list at the moment. The outcome of that issue will not automatically make the functionality available in Grasshopper but will give David the information he needs.

In RhinoCommon from HiddenLineDrawingSegment::ParentCurve.SilhouetteType the silhouette types are Crease( should probably be called SilhouetteCrease) vs NonSilhouetteCrease. The meaning of these terms are:

Crease - An edge of the geometry where two faces come together and the faces are not tangent along the edge this is a property of the geometry only, view independent.
SilhouetteCrease - A crease in a specific view in which along the common edge one of the faces is occluded by the other face.
NonSilhouetteCrease - A crease in a specific view in which along the common edge both faces are visible ( or equally visible).


Just making sure @DavidRutten sees this last reply…