HMorton posted at 1:10PM Sun, 09 August 2020 - #4396382

So I'm guessing you used edge crease on that model in the other thread but if you didn't use support loops and need at least 3 edges to crease a vertex into a point with edge crease, then how did you make the points on that other model? I only see two edges connected to those points. Another question while I have your ear is about that sharp edge thing. You gave sharp edges to two edges in that example, but I don't see any change to that object at all. I know you said it only works for smooth shading but what good is that really? I mean what would be a practical use for it then?

I'll try to answer in order of your questions here:

1. The other model does actually have 3 edges at every point. Don't forget there is a thickness to the model. That means at every point there is at least one edge for the extrusion. That's the edge I used as a creased edge to maintain a sharpened point when subdivided. There are no support loops but I would include support loops if I was going to export the model, because not every software will recognize edge creases in the OBJ import. FBX could be a different story.

2. The reason you don't see any change in the subdivided cube model with the Mark Sharp edges is that I was trying to illustrate the difference between Crease Edges and Mark Sharp edges when it comes to subdivision surfaces. Mark Sharp edges do nothing for subdivision by itself. When you mark an edge "sharp", you need to enable Smooth Shading on the object first, then go into the Object Data tab in the Properties panel and turn on the Auto Smooth option. Now when you subdivide the model, you will see a sharp shading transition at the area you marked as sharp. If you don't enable Auto Smooth, then you will see nothing. No Changes. The thing is, nothing is actually happening to the geometry of the mesh like it does with Creased Edges. Instead, it's just changing the shading of the object to create a harsh transition whereever you marked an edge sharp. Kind of like using flat shading in just one selected area of the model. Here's a visual example:

The reason someone would want to do this is the same reason people would want to create Smoothing Groups on a model in other software packages. It's mostly for low polygon modeling purposes, to give the illusion that there is a sharp edge without actually adding new geometry, or without actually changing the shape of the geometry in any way.

Hope that clears it up for you.

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