To cross or not to cross faces...

[Kaluura Boa]

That is the question. Is there some hidden contraindications against crossing faces?

Let's take a (stupid) example to illustrate my question: I made a nice heart and I want to add an arrow across it.

I have 2 solutions: I can make 2 objects in one mesh where some faces of the arrow will cross some faces of the heart, or else I can add vertices, edges and faces to join the heart and the arrow into a single "inflatable" object.

I checked in-world already and crossing faces come out right visually. That makes me wonder: Why should I make a heavier object if I can just let the faces cross?

 

[Gaia Clary]

There is nothing wrong per se with crossing faces. In your example i would go the same way, create a heart, an arrow and do not care about crossing faces. However this is not a general advice. At the end it depends on what you want to achieve.

maybe you would want to make heart and arrow one object to make it a 1 prim build. Maybe you need the arrow separately because your build is animated ... "arrow flying into heart" would come to mind

So you have to judge case by case...

[Maeve Balfour]

Faces which cross THROUGH each other (which is what I assume you mean here) isn't a problem at all - I do it all the time with my SL meshes. It definitely helps reduce triangle counts, and I use this method to eliminate duplicate faces wherever possible (texturing intentions allowing).

As a simple example, if I have a single mesh object consisting of a row of windows in a long wall (with the windows separated by pieces of wall between each instance), I will stretch a single long pane of glass between all of them as a single shape (two triangles per side of the glass - four triangles in total). If I plan it carefully, and space the windows evenly, I can make use of a repeating window texture (with blank texture space where the non-visible pieces of glass will be). The glass section of the mesh itself will be narrower than the wall sections, so it will be hidden within the wall cavities where applicable. This example (wall section with windows and glass) I would upload as a single mesh object (with suitable LODs), hence the importance of reducing the vertice count. Compared to having individual glass pieces PER WINDOW, there can be a considerable saving - of course this depends on the layout etc, since nicely spaced windows might not be what is intended.

But yah, definitely utilise this to the maximum - you'd be surprised how many vertices you can reduce by eliminating duplicates. The only potential issue might be Z-fighting in rare circumstances (flickering faces, but this would only be for faces occupying the exact same space where they cross over, and is easily worked around with vertice shifts).

:matte-motes-smile: