 # Vertex normal

Is there a method to display the vertex normals in sketchup? I am interested in inserting components into all vertices of regular or irregular polyhdrons (e.g. dodecahedron, geodesic dome). In order to align the axes of the components with the vertices, however, I need the vertex normals of the respective vertex point. Vertex Tools > Show Normals with Skatter

If your question has more to do with the Developers section, at least you know it can be done.

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@mihai.s, thank you for your input. To my understanding, “show normals” from “vertex tools” only shows the normals of all the faces connected to a vertex but not the normal of a vertex. In my understanding the normal of a vertex is derived from the average of all normals of all the faces connected to a vertex (or something like this) and should be displayed with only a single line. Like in the picture from wikipedia.

Also, the vertices displayed in vertex tools are not usable because they don’t scale when I zoom in and thus I can’tuse them to align an axis of a component to them.

Yup, I’ll try that.

I tried a method to find the normal to a vertex. It might prove complex but it seems to work. See this SU file for ideas.

Vertex normal.skp (99.2 KB)

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@jean_lemire_1 Thank you very much for your input. The method you suggest is interesting but as far as I can tell this only works for vertices based on “regular shapes” like vertices based on lines of equal length an angel between them (or something like that).

I think this does not work for vertices on a sphere like this:

However I think JointPushPull with the setting Finishing: THICKEN: “Keep original faces and reverse if necessary” does the trick?

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Yea, that looks really good!

How do you determine the angle of a vertex normal. My idea was good for a regular polyhedra but for an irregular one, how do you proceed ?

Do you calculate the average angle of the faces meeting at a vertex ?

Do you calculate the normal of an edge (average of the two adjoining faces?) and then the average angle of these normals for the edges meeting at a vertex ?

@jean_lemire_1

I have started with my human intuition that tells me that there could be a line protruding from each vertex that “doesn’t look crooked”. However I am not a very mathy person so I also don’t know how a vertex normal is actually calculated. I am also not sure if there are multiple reasonable methods that give different results.

But I think it is like you suggest. The first step is to calculate the average angle between all of the faces that make up the vertex, and then to average them all.

For the record, SketchUp doesn’t store normal directions for vertices.

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