Difference Between Feature Angle and Vertex Angle

Gnokrojam

I am creating a triangle shell mesh for tet-meshing. When using Automesh to mesh elements with QI optimize, one can specify a feature angle and a vertex angle. The feature angle is the angle between element normals.

What about the vertex angle? The manual says: ' Whenever an element vertex exceeds this angle while adhering to features, the element will be split into two elements with correspondingly smaller vertices.' The default angle in the field is 30 degrees. Triangles will always have an angle that is greater than 30 degrees. Someone else in the manual it is described as being similar to the feature angle. I can't find an illustration or more detailed explanation of vertex angle. Can someone clarify this for me, please?

Thank you.

Phil

tinh

Hi

Vertex angle is angle between element's free edges

Gnokrojam

Do I understand correctly that it is the angle between the edges of two different elements?

 

If one had a mesh of all equilateral triangles it would be a very good mesh. All of the angles will be 60 degrees. The panel came up with a default vertex angle of 30 degrees. That would require that all of those equilateral triangles be divided again. That doesn't make sense to me. Either I don't understand the vertex angle, or it should be set to something greater than 60 degrees.

Gnokrojam

Ah wait, you said free edges. I have to think about that.

tinh

I remember that not only free edges, but also feature elements are taken into account

note that vertex angle  is angle between 'feature elements' , it is not 'feature angle'

to see feature elements, enter Tools>feature,  it appears depending on feature angle

Gnokrojam

I found the Tools>Features panel of which you spoke. I didn't know about it, and it can be helpful.

It doesn't help with vertex angles.

I appreciate your help, and feeling like I'm really being dense about this, but I'm not getting it.

I have attached a screen shot of a model I am working on now. I have shown the features. Maybe you can point out or describe vertex angle from it.

Thank you.

<?xml version="1.0" encoding="UTF-8"?>

tinh

Hi,

this captures may help you figure out vertex angle:

these are vertex angles: 

 

 

 

when automeshing, I set feature angle to 90D while vertex angle kept 30D, you can see inside features were neglected

but outside free edges not changed, because vertex angles>30D make vertices (yellow nodes) become anchor nodes

 

Gnokrojam

Very good illustrations. I think I see now.

 

I appreciate the time you put into this.

Thank you very much.

 

Phil