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I just started using blender again and I'd like to know if smoothing your model out adds a performance hit to your game?

By smoothing I mean when you hit ctrl+X (number from 1-9). The number of vertices stay the same, but the model gets considerably smoother the higher the number goes, i'm wondering if it's secretly adding tons of vertices in order to do this and would be a performance hit, or if it's doing something else that isn't a big deal to the performance of your game. Thanks.

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  • \$\begingroup\$ Couldn't you test this out pretty quickly by exporting one of each and seeing how many vertices are in each of the exported files? You rarely get something like this for free, so it's likely adding vertices. \$\endgroup\$ – MichaelHouse Jul 17 '13 at 23:41
  • \$\begingroup\$ Hmm, I'm not really sure how to find out how many vertices my model has by opening the file, but I did notice that the file size difference is massive so I think it might be adding vertices after all... \$\endgroup\$ – user1157885 Jul 18 '13 at 3:13
  • \$\begingroup\$ That's one way. \$\endgroup\$ – MichaelHouse Jul 18 '13 at 4:03
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It dependes what kind of smoothing.

I don't know about new versions of Blender, so I don't know the functionality you are talking about, but it sounds like it is keeping the mesh the same but using it as a base mesh for a high resolution smooth surface. The number of vertices are the same, but a high res smooth surface is constructed at as a preprocessing stage while rendering.

However, (although I don't think you are talking about this) setting smoothing on a mesh's material can mean fewer vertices, since shared vertices can be reused (if the position, normal and uv coordinates are the same).

So to summarise:

Any kind of subdivision smoothing -> more vertices

Setting material smoothing flag -> fewer vertices

However, if you are using subdivision, when you export it may just export the base mesh. You may need to apply the subdivision modifier to be able to export the smooth geometry. Why don't you just look at the number of vertices and number of triangle when you export?

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  • \$\begingroup\$ Ctrl-X sets the "View" subdivision level in Blender. I'm not sure whether the View-level or the Render-level is used by the export scripts. \$\endgroup\$ – Jimmy Jul 17 '13 at 23:13
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Summarizing:

  • Ctrl-x adds a sudbivision smoothing modifier. You can see it in modifiers well after the press of aforementioned key.

  • It will either have an negative impact on performance (in the case where
    export applies subdivision) or will not (when subdivision is not
    applied). But in the latter case you will have an unsmoothed mesh in result. If you want to smooth mesh without vertices number change, you may use vertex smooth in edit mode.

  • Number of vertices you see in the top window is a number of vertices before modifier application, so think of them as of "control
    vertices", not the resulting mesh vertices, so the number of vertices is not the same, in fact.

  • Whether modifiers are applied or not is controlled in export settings, usually.

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Yes, it does reduce performance

What you are actually talking about is subdivision surfaces. This generates more geometry to give the mesh enough geometry to round itself out. To see how this modifier affects your mesh.

Subdivision Surface (Subsurf in short) is a method of subdividing the faces of a mesh to give a smooth appearance, to enable modeling of complex smooth surfaces with simple, low-vertex meshes.

You do not want to subsivide meshes for use in realtime applications for obvious reasons. If you are interested in getting smooth looking meshes, you can use the Smooth modifier instead as this moves vertices rather than adding more.

...The number of vertices stay the same, but the model gets considerably smoother the higher the number goes...

The number of vertices do not remain the same, look in the header and you will see that the vertex count has gone up, set your model to flat shading and you will also see all the new faces as the levels fo up.

Also, you can subdivide up to 6 levels in Blender. The view level is the one you see in the viewport and the render level is the one you see in the game engine or render etc.

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