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Questions about how UE4 handles triangles of a model, and the outcome

Hi guys, I got some questions about how UE4 handles the triangles of models: In the screenshot, the number of vertices and triangles of my models looks weird. The tris are about two times more than the vertices, isnt it suppose to be less than vertices? Is that normal, is it how UE4 handles geometries? Or is it becuase I modeled the object in a wrong way and caused this incorrect result?

In additional, when I modeled these geometries, they had tris back in my modeling software Blender, I didnt model them with quads, will it effect the performance or shading in UE4? For UE4, which method would be better for the modeling and engine? Quads or Tris? If Tris will effect the engine, should I go back to redo all of my modeling works (They all have tris in Blender)?

Thank you, sorry for my bad English. alt text

Product Version: UE 4.8
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strange tris.png (81.3 kB)
strangetris(2).png (73.7 kB)
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asked Nov 21 '15 at 08:23 AM in Using UE4

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ALTWang
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if every triangle in your model was separated, you would get 3 times as many verts than tris. in most models, you have many triangles sharing edges, so adding an extra triangle might add only 1 more vert. using free verts that don't contribute to triangles is bad practice, so you will always have at least as many verts as tris, and up to 3 times as many verts as tris. so there is nothing wrong with the numbers you are getting.

every model in game is rendered as tris, so it doesn't matter if you import the geometry from quads or tris, they will become tris in the engine. now, if you want more control over edge flow, you probably want to manually convert some of those quads to triangles before export, because blender doesn't allow you to turn hidden edges like 3ds max does, and some of your quads might bend in the wrong direction, causing distorted normal maps or bad deformation or bad silhouettes on organic objects.

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answered Nov 21 '15 at 01:49 PM

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ScottSpadea
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avatar image ALTWang Nov 21 '15 at 07:34 PM

Thank you Omni. I have few questions, what does it mean about the "using free verts that don't contribute to triangles is bad practice", I just started learning modeling, so I dont understand what a free vert is. Also about the " blender doesn't allow you to turn hidden edges" I dont know what the hidden edges are and what are they designed for. Could you tell more about these terms? Thank you!

avatar image ScottSpadea Nov 22 '15 at 07:25 PM

a free vert would be any vertex that is not part of a triangle, its just a vertex floating in space by itself, without anything connected to it. they are useless. all verticies should be connected to some kind of face. to see an example of a free vert, you can go into edit mode, select a single vertex, and use ctrl+D to duplicate the vertex. you will get a new vertex that isn't part of a triangle, and there is no reason you would ever want a free vertex in a finished game model, but it may be useful for modelling things, if you want to draw shapes vert by vert, then connect them into faces.

every quad or N-gon (faces with more than 3 points) are built out of triangles, but in your modelling software, some of those edges are hidden. in blender, there is no way to control the direction of these hidden edges, so you sometimes have to cut into quads to make their triangles face the right way.

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