I was searching for how to create smoothing groups in Blender, and everybody seems to say I should use Edge Split. But this will actually create new edges, destroying the topology of the object! Is the situation really so that I cannot create 'smoothing groups' without modifying the actual topology of the object? It will be very difficult creating models for game engines or exporting to other 3d software without smoothing groups, and I don't want to destroy the topology to achieve it either..

Here, I start with a smoothed sphere:

smoothed starting object

I then apply edge split on a face, as is recommended as blender's method of doing smoothing groups:

edge splitting

This is the result. Looking good so far...:

edge split result

Then I try to select an edge loop here, but it stops on the affected area!

edge loop

When I try to move one of the edges, the reason becomes clear: Two edges have been created, completely destroying the object's topology:

topology destroyed


I suggest you use the modifier Edge Split instead. In Edit mode, select your edges desired to be sharp. Hit Ctrl+E to bring up the Edges menu. Select Mark Sharp. Now add the Edge Split modifier.

How to mark edges sharp

Edges are split by the modifier. In Edit mode they are marked cyan. Topology is still fine:

Fine topology

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    $\begingroup$ Would be good if you elaborated on why modifiers are different/better. $\endgroup$ – Alistair Buxton Nov 11 '13 at 2:01
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    $\begingroup$ Modifiers alter the mesh when it comes time to draw or render, leaving your mesh unaltered when you go into edit mode. Makes things a lot easier to undo or adjust. $\endgroup$ – sambler Nov 11 '13 at 12:27

Since this question old I figured this might relate to an old version of blender. So here's an updated answer.

The Autosmooth functionality was added a couple of blender versions ago (current 2.79), it enables you to set whether or not the edges are being smoothed by the smooth shading or not without using any kind of modifiers or actually editing or splitting the edges. enter image description here

The steps how to use the autosmooth functionality

Step 1. Shade the object to smooth shading

Step 2. Go to edit mode and select the edges you to retain its sharpness

Step 3. Press CTRL+E to bring up the Edges menu. Click on Mark sharp.

Step 4. Now go to the Mesh data tab under the properties panel and enable Autosmooth under Normals. You can set the angle of smoothing to your liking but I like to keep it at 180°.

The blendfile:-

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    $\begingroup$ This is the ideal solution and should be the top answer. Marking smoothing seams without splitting the topology actually makes this method superior to smoothing groups IMO $\endgroup$ – dexgecko Jun 11 '18 at 16:13

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