JeremyR
I think this may be an on-going issue but Im not sure whether we have found a solution or not yet.

So I am animating an ocean texture and using the outAlpha to delete faces on a mesh, then extruding that mesh. Face and edge IDs will be changing all over the place. What I want to do is detect the changing edges on the fly, Ive selected a portion of the edges Im referring to. Using a couple of group nodes with filter doesnt work because the extrude happens after the delete and if I switch those two around the delete doesnt work at all.
Click image for larger version - Name: Screen Shot 2017-12-12 at 10.26.49 AM.png, Views: 8, Size: 244.42 KB
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JeremyR
Scene attached
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rolfcoppter
Hey Jeremy,

I have done something like this very recently to setup a procedural bevel I will see if i have time today or tomorrow to take a look at your scene and implement what i used but first.....

Which edges exactly are you looking to select? From the look of it you are trying to grab only the outer edges of your mesh that don't follow the shape of the sphere? is that correct or is there another rule your looking to follow?

Also what do you plan to do with those edges? just so i can test if its working or not?
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JeremyR
Hi,
The edges in question are the result from a deleteComponent which is animated. I want to be able to extrude or bevel these edges. I think last time we tried to work it with the tension map but this node requires a reference node and in this setup because of the extrusion and deleted faces it wont work I dont think. Anyway the scene is attached in the above post, thanks for taking a look.
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rolfcoppter
Hey quick UPDATE,

I had some time so i quickly made a scene for you, this is the selection i got. Let me know if this is what you were thinking? Edge_selection.png 
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JeremyR
Awesome I can work with that - Ill take a closer look - thanks!
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rolfcoppter
if you have any questions or need help taking it further let me know
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JeremyR
Great. Any ideas on how to control the angle of extrusion? Ideally want it to extrude out from object centroid.



Screen Shot 2017-12-13 at 2.02.06 PM.png 
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rolfcoppter
it looks like it already is by default.
Edge_selection.png 
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JeremyR
No I wasnt very clear here. I managed to isolate the edges to only the ones on the outer shell and want to extrude that new selection. As you can see the extrusion seems to take off at odd angles rather than align to the original extrusion. For some reason I thought the extrusion was based on average of vertex normal but it looks like Im wrong here because an AttributeTransfer has no effect of extrusion direction.
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JeremyR
Outer shell isolated edges...
Screen Shot 2017-12-14 at 2.15.11 PM.png
 
Extruding those edges dont conform to surface normal
 
Screen Shot 2017-12-14 at 2.15.31 PM.png 
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rolfcoppter
can you upload a new example after you have isolated just the outside edges? il take a look and see what i can do 
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JeremyR
Thanks, here you go.
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plarson
I noticed one way to avoid that is to use deleteComponents after the face extrude to provide a shell boundary for the Group node to then extrude the edges from. Here's your scene with that way of getting the boundary. Deleting newly extruded faces and inversely all but newly extruded faces, in two branches, operating on each separately, then uniting them before the output. ma Edge_ Detection.0001.ma     
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JeremyR
Nice one Peter! thanks
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