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Subject: Making pointy edges with subdivsion?


HMorton ( ) posted Fri, 07 August 2020 at 9:06 PM · edited Mon, 25 November 2024 at 3:29 AM

Ok, thought i would make this thread after reading one of the other threads here. My question is this.... if I have a model that contains curvy geometry but I want to keep certain parts pointy and sharp while still using subdivision surfaces how is that done in Blender without adding more edge loops or creasing edges??? It doesnt seem possible to keep an objects points sharp using subdiv modelling in blender without creasing edges where it should be smooth, or without adding support loops and extra geometry!


RedPhantom ( ) posted Sat, 08 August 2020 at 7:09 AM
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sharp.JPG

Try putting a second edge close to the first like in the image


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Lobo3433 ( ) posted Sat, 08 August 2020 at 9:52 AM
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Another way if you do not want to add more loop cuts is to mark a seem sharp especially useful in conjunction with Bevel modifier select the edges you want to keep sharp right click and you will see the mark sharp down towards the bottom of the menu it should retain a sharp edge after you add a subsurf or bevel

Screenshot_1.jpg

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LuxXeon ( ) posted Sat, 08 August 2020 at 1:22 PM

@HMorton I think I know what you're looking for here, but please correct me if I'm wrong. The examples shown above are the only way to get creasing and sharp edges and points in Blender. However, I think you're referring to a feature called "Vertex creasing", which is something a little different? Vertex creasing is a feature people may be used to in Maya or 3dsmax when using OpenSubDiv (the open-source Pixar version of Subdivision Surfaces). It is different from edge creasing in that you can select just one point or vertex on the model and give it a weight value so that when you subdivide, it will force the subdivided geometry into a creased point around that selected vertex, without any additional geometry or edge sharpness. It is very useful when modeling lower polygon objects.

Blender has the OpenSubDiv implementation of Subdivision Surfaces available only when using the "Cycles Experimental" version of the subdivision surface modifier, but it is only using the "adaptive" features of the modifier. In other words, vertex creasing is not available in any version of Blender that I am aware of. I do know that it has been asked for many times over the last couple years, because people who had been using 3dsmax or Maya are very used to having it, and it allows you to do some things that simple Edge Crease can not do.

Hopefully, this answers your question. It just isn't in Blender yet, but if you look up Blender Vertex Creasing, you'll see that it has been brought up many times in the past and hopefully will make its way into the software very soon. For now, just use one of the methods above.

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LuxXeon ( ) posted Sat, 08 August 2020 at 1:56 PM

Oops. I just noticed something. Lobo3433 example is showing the Mark Sharp feature, which is commonly mistaken for Edge Crease but really has nothing to do with Subdivision. The Mark Sharp feature has to do with how an edge looks when you apply Smooth Shading only, and will make edges appear sharp after smooth shading is applied. It won't affect the actual geometry with subdivision. Edge Crease (Shift+E), on the other hand, will actually change the influence of the geometry based on a factor input variable of your choosing after a subdivision surface modifier is applied. It does something similar to the Vertex Crease, but unlike Vertex Crease, which Blender does not have, Edge Crease also influences geometry around those selected edges to create either a point or a sharp edge on subdivided geometry.

To illustrate the difference, I've included this screen capture below. It shows two cubes with subdivision surface applied. One cube has two edges with Edge Crease set to 1, the other has the same edges with "Mark Sharp" applied:

creasevssharp.jpg

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LuxXeon ( ) posted Sat, 08 August 2020 at 3:23 PM · edited Sat, 08 August 2020 at 3:33 PM

@HMorton again. I saw your post in the other thread, so I will include another example of Edge Crease below. This time, let's say you want to keep or create a point instead of just creasing or sharpening the edges of the subdivided cube.

Below are two examples. Both are just simple default cubes with Edge Crease on certain edges. If you want to create a pointy edge, then you need to create 3 Creased Edges which all point to the same vertex. This is where Vertex Creasing would come in very handy, but we don't have that ability yet, so this is the only alternative. Yes, you can use things like bevel to create the same effect, but then you're adding more than just one extra edge to the model.

edgecrease.jpg

Let me know if this makes sense.

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HMorton ( ) posted Sat, 08 August 2020 at 8:18 PM

Thanks Luxxeon, that's what I wanted to know. I was searching all over for a way to crease vertex without more geometry and then I realized there just wasn't one. 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? Sorryu for all the questions and thank you to everyone who tried to answer. And thanks for your help luxxeon! I used a few of your freebies years ago and they were great models.


HMorton ( ) posted Sat, 08 August 2020 at 8:28 PM

Oh one last thing Luxeon, promise! hehe. In your example where you create a point from the subdivded cube by creasing 3 edges, why did you create a new edge instead of using the third edge that was already connected to that vertex? Why bother adding new geometry to the box when there is already 3 edges connected to that vertex? I'm sorry if I'm being a pain here. I'm just trying to grasp that. I used Blender years ago back when it was still in 2.7x days. Then I switched over to Maya for a while and got used to that. Then I came back to Blender recently and I'm all messed up with the workflow now. It's so strange to me now and I just can't work like I did with Maya. I even played around with 3dsmax for a while which I enjoyed a lot but upgrading became way too expensive. Thank you again for the help. Also thank you to all the blender users here! This is a really great and personal forum compared to other Blender forums!


LuxXeon ( ) posted Sun, 09 August 2020 at 1:31 PM · edited Sun, 09 August 2020 at 1:34 PM

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:

autosmooth.jpg

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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LuxXeon ( ) posted Mon, 10 August 2020 at 12:42 PM

@HMorton I almost forgot one other thing when it comes to the Mark Sharp feature. Once you enable Smooth Shading, you need to also enable Auto-Smooth for Mark Sharp edges to work. However, there's an alternative in the form of using an Edge Split modifier. If you mark edges sharp on any mesh, you can just apply an Edge Split modifier with "Sharp Edges" checked. You won't need the Edge Angle checked in this case, as long as you have marked edges as sharp.

Here's an example of that:

edge_split.jpg

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HMorton ( ) posted Mon, 10 August 2020 at 9:02 PM

Got it. Thanks, Lux. I gotta be honest I'd never have figured out how to use the sharp edges. Crease edges make more sense to me and seem to be a lot more useful because they work with subd without anything else to worry about. Plus it actually affects the edges.


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