Blender "sharp" edges ignored when uploaded to SL?

[Cubey Terra]

I hope this question hasn't been asked before, but I can't find it in the forum.

When I mark an edge in Blender as "sharp", I then uploaded it into SL and the edge isn't sharp anymore. Do I have to actually split the edge (duplicating the vertices) to achieve a sharp edge? I don't really want to do this for various reasons. Hoping there's an easier way to achieve sharp edges.

[Drongle McMahon]

If you mark the edges as sharp AND add the edge split modifier, probably with marked edges checked but not angle, then Blender will shade the mesh as if the edges were split, but they won't be split for normal editing*. Then don't apply the modifier, but when you export with the Apply Modifiers option checked (automatic for the SL presets) the edges will be split in the Collada file. Sharp edges have to be split in the uploader anyway, so you shouldn't notice.

In contrast, if you use Edge split from the menu or shortcut, it as applied immediately.

There is another way to get sharp edges, by checking the Auto smooth in the Normals section of the object properties tab (the little triangle mesh icon). This will make them sharp depending on the angle set there, and if they are marked sharp. This also lets you see the split vertex normals in the 3D view. However, in the version of Blender I am using (2.71)  the collada exporter does not recognise sharp edges made that way. That may be corrected in later or upcoming versions of Blender. I hope Gaia will let us know.

*They will be split as far as subsurf modifiers further down the stack are concerned. So if you want to subsurf, it has to be above the edge split.

[Cubey Terra]

This is a very helpful response, Drongle. Thanks.

I was using Edge Split from the Edge menu, and of course that wasn't what I wanted. I don't yet know about "modifiers", so I'll look into what those are and how to use them.  I saw the "Apply Modifiers" option in the Collada export, but didn't know what it was. Now I know!

The Autosmooth feature works wonderfully in Blender for most edges, but as you said, those sharp edges don't seem to make it into SL.

OK. Time to read up on what modifiers are. 

[Drongle McMahon]

You get the list of modifiers by clicking the little spanner/wrench on the icons of the Properties panel, which is usually on the right of the screen, and clicking the Add Modifier button. Lots of nice things to play with there.

[Cubey Terra]

What you suggested worked very well. Next question: How do I undo it? For example, if I've sharpened edges in the wrong place. How do I remove that modifier? I don't see a list of modifiers that have been applied to an object.

[Cubey Terra]

Doh. I just realized that I wasn't supposed to "Apply" the modifier. That splits the edges immediately. I just need to add it to the object's modifier list, set the settings, and leave it there for when I export. :matte-motes-bashful-cute-2:

[Drongle McMahon]

Yes. Although you can undo it - just go into Object mode and do Ctrl+Z until the modifier comes back. Of course you lose anything in between as well. We used to have to Apply, export, and then undo every time. Now the exporter essentially does that for you.