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Model 1 — all 4-sided polygons Gun Model 1 Wireframe Gun Model 1 Wireframe Gun Model 1

Model 2 — polygons have arbitrary number of sides/vertices Gun Model 2 Wireframe Gun Model 2 Wireframe Gun Model 2

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    \$\begingroup\$ short answer is: the edges you deleted, will be automatically filled up by the computer because computers only work with triangles. but you still want to always use quads because faces that are not quads or triangles can get baddly deformed when triangles are automatically added by the game engine. \$\endgroup\$
    – Cei
    Jun 29, 2023 at 10:29
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    \$\begingroup\$ @Cei If the model is not deformed, the model is not badly deformed. Animation can introduce deformation (be that skeletal animation, morph target animation, or procedural animation), which could go wrong if the topology is wrong. But if the model will not be deformed at all, then you can relax your topology concerns. \$\endgroup\$
    – Theraot
    Jun 29, 2023 at 10:51
  • \$\begingroup\$ Expanding on Theradot's point, suppose one starts with a regular hexagon connecting 12, 2, 4, etc. positions on a clock, and one fills it in by drawing a triangle connecting 12-4-8 (also creating 12-2-4, 4-6-8, and 12-8-10), and then moves the 12 o'clock point out of the plane. Think how the structure would flex. Now imagine if one had instead drawn lines connecting 12 to 4, 6, and 8 (creating 12-2-4, 12-4-6, 12-6-8, and 12-8-10) and think how the structure would flex then. \$\endgroup\$
    – supercat
    Jun 29, 2023 at 17:37

2 Answers 2

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It doesn't really matter. 3d models with faces that have more than 3 vertices don't really exist in 3d graphics*. They are a usability-convention of the modeling program. 3d rendering engines can only render triangles. So when the model is exported from the modeling program and into a game engine, all non-triangular faces get broken up into triangles anyway.

Too many superfluous edges on a surface can of course result in more triangles being generated than necessary, which can negatively affect performance. But that doesn't seem to be the case here. The edges all seem to be in places where the triangulation phase would generate edges anyway.

*Excluding some really exotic rendering techniques you usually don't see in mainstream 3d games

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  • \$\begingroup\$ Don't some programs model with quad meshes instead of triangular meshes? I vaguely recall this in a computer graphics course I took. \$\endgroup\$
    – qwr
    Jun 29, 2023 at 21:43
  • \$\begingroup\$ @qwr Model? Perhaps. But certainly not render. \$\endgroup\$
    – Philipp
    Jun 29, 2023 at 22:07
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    \$\begingroup\$ @qwr, a number of pre-OpenGL rendering systems used quads, but because of issues with quads such as non-planarity, every mainstream system these days uses triangles for rendering. \$\endgroup\$
    – Mark
    Jun 30, 2023 at 1:03
  • \$\begingroup\$ Well the question is about modelling, not rendering. I did find some papers with some purported benefits of quad meshes. \$\endgroup\$
    – qwr
    Jun 30, 2023 at 14:35
  • \$\begingroup\$ @qwr Well, my argument is that it does not matter what you do during modeling, because the rendering stage will turn n-gons into triangles anyway. Why not write an answer based on the content of those papers you found? \$\endgroup\$
    – Philipp
    Jun 30, 2023 at 14:36
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If you are using proper topology, then the number of faces and vertices will always be roughly the same. Eventually, if your model has 0 triangles and only quads, the vertices and the quads will be almost the same amount. In the image the quads are roughly 2200 and the vertices 2100. This is only because the model is sliced into pieces. Otherwise the numbers would be more even.

Screenshot of a character model in Blender

Your computer is only calculating where each vertex is located and how it moves. And then it fills up the space between. You really only have to think to always work with quads and never with any shape that has more than 4 vertices.

Triangles are fine, but only to save geometry so use them sparingly.

If your geometry has too many vertices, just press M, select "merge by distance" and set the distance to 1 millimeter.

If your geometry has shapes with more than 4 vertices - pentagons and such things - press space and search in the bar for "triangulate faces". Then press again Alt+J to transform the triangles into quads.

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  • \$\begingroup\$ Do you have any reason why you wouldn't want triangles? \$\endgroup\$
    – Rick
    Jun 30, 2023 at 11:11
  • \$\begingroup\$ @Rick harder to decimate models if you want to make lower polygon versions, harder to add lopps if you want do add new geometry, if you animated the thing... triangles don't bend well... if texture the thing... texturing is easier when your UV is mostly just a grid of squares.... especially in blender where you can Unwrap from perspective view to match the 2D UV perfectly with the 3D aspect ratio \$\endgroup\$
    – Cei
    Jun 30, 2023 at 13:42
  • \$\begingroup\$ more on texturing, if you for example stencil texture the face of someone like I did in my above images... triangles can make the face look way more deformed than it should. \$\endgroup\$
    – Cei
    Jun 30, 2023 at 13:44
  • \$\begingroup\$ Thanks! I think those add a lot to your answer. \$\endgroup\$
    – Rick
    Jun 30, 2023 at 18:31

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