Select Edges In Empty Faces?

What does Select Edges In Empty Faces select? What is an empty face?

Hi Tiles,

It is based on triangulation and/or the underlying triangulation.

Some pics needed for simple example:)

Created a segmented box:-


Selected one of the corner vertex and moved/snapped it to the adjoining vertex.(not welded)


In sub_object edge mode > "Edges in Empty space" highlights edges:-


To understand the result, you need to check the underlying triangulation (vertex order/windings)

If I triangulate the object(which shows the underlying triangulation), moving the vertex along the blue arrow to snap it to the adjacent vertex, the 2 edges also move along the red arrows, which cause those 2 moved edges to overlap the other 2 edges.

That causes 2 triangles to have an edge of zero length, and it can then be said that those 2 triangles are empty, with no visible polygon. The edges selected by "Edges in empty spaces", are the remaining edges of those triangles.

Thanks Steve. So that`s micro tesselation. The names in Nvil are really killing me

I wouldn't choose the phrase "empty space". At first I had an association of edges from outer space.
For me it's more comprehensible if it was called "zero face area" instead of "empty spaces". But then again: if the mesh is not triangulated like in the example with the cube, there are no polygons with zero area, just an edge with zero length.
The more important question for me however is: What is this selection actually good for?!
If I have vertices and edges overlapping I most likely would want to merge/weld them. So what do I do with a selection like this? I'd like to be enlightened, because I can't think of a practical use.

And it doesn't work for a simple plane or a basic cube?

But then again: if the mesh is not triangulated like in the example with the cube, there are no polygons with zero area, just an edge with zero length.

The triangulation I made was to show the underlying triangulation that many applications use. Although just about all 3d applications show quads/n-gons, many still have a need for underlying triangulation that they make, usually from the vertex order/windings. It is why it is usually advisable to avoid concave quads (although NVIL uses the term for concave quads for something different)

because I can't think of a practical use.

Then do not use it.

And it doesn't work for a simple plane or a basic cube?

Just checked on a basic 6 sided cube, and appears to be working correctly.

Then do not use it.

When i don`t know what a tool is good and meant for, how can i use it then?

Then do not use it.

When i don`t know what a tool is good and meant for, how can i use it then?

Did I reply to you, or to your original question of the tools function with "Then do not use it"? No.
My reply was to a specific statement of "I can't think of a practical use" after being shown the use/function of the tool.
So, if you know how a tool functions, but cannot think of a practical way to use it, then do not use it.

Did I reply to you, or to your original question of the tools function with "Then do not use it"? No.

Huh? Did i attack you?

So, if you know how a tool functions, but cannot think of a practical way to use it, then do not use it.

No. The logical conclusion is to ask what this tool is good for then. Which Vaquero did. And which is something that i second. Somebody must have asked for this tool in the past. So there must be a need for it. A case where it is useful. And i am curious in what case this is useful.

No one asked this tool. It's my own idea. I think it provides a way to check the mesh if you suspect that it may have this kind of geometry and want to find them and fix it if needed.

I see. Thanks

For me it makes no sense to explicitely select this trouble geometry first. You may want to fix it directly. In Blender this does the Remove Doubles Tool. In trueSpace this job does the Heal Vertices Tool. They hunt through the vertices and fix exactly those cases that you select with your tool here, by welding the involved neighbour vertices together.

The logical conclusion is to ask what this tool is good for then.

Huh?
It is a selection tool that selects what it was implemented for.

Yes. But what is this selection good for? You cannot work with this geometry in any way.

Yes. But what is this selection good for?

For doing what it was intended for.
 

You cannot work with this geometry in any way.

But it is possible to get such geometry inadvertently, possibly as example, when using such tools as "Tweak>move". Would you really want to possibly change poly flow by blindly welding[remove doubles] instead of checking for such bad geometry?