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View Full Version : SubD Catmull clark not so good



Tyler007
02-07-2007, 02:01 PM
I was wondering if anyone else was having problems with this add on to lightwave. I will add edges and then the object will split at the edges what’s the deal?

Earl
02-07-2007, 02:24 PM
The implementation is a little flakey right now. I would only use them if you absolutely have to, and if that's the case I would do all your modeling first, then as the last step add edge weights (many tools will break the edge weighting on CC subDs right now).

Surrealist.
02-07-2007, 10:14 PM
I actually don't use old subd anymore. I have had great sucess with Catmull-Clark once I got used to how it performs, what it will and won't do. I have come up with a work flow that works for me.

First off I have found that you can't abuse it. It does follow some basic laws not to dissimilar to the way regular subpatch mode works. It will break apart if you have a mesh that is causing stress in an odd way. So if you add edges you might have a temporary hole.

As for edge weights, I have not had any success at using it to create predictible shapes that did not have smoothing errors. But I found the same to be true with subpatch weight on points - useless.

Seems the holy grail is to be able to create sharp edges without using geometry. I have not found that yet with any technique other than sensible modeling. That does not mean that edge weights don't work. I just have not had sucess.

What I miss in Catmul-Clark is the ability to grab vertices on the mesh. Even with cadges on you can't get at some of the points. So what I do is select all points and edit that way. Miraculously I am able to drag points that are under the skin. This is the only saving grace. As for concentration of detail that is its biggest plus. But again rules apply to step down your mesh gracefully and without erors. Just as with standard SubD. (still working on mastering that in CC)

All and all Catmul-Clark is far superior to subpatch in it's overall look - to me. I look forward to better implimentation. All that said, I have not put it though the paces with endomorphs or bones. So that is yet to come.

Earl
02-07-2007, 11:59 PM
All and all Catmul-Clark is far superior to subpatch in it's overall look - to me. I look forward to better implimentation. All that said, I have not put it though the paces with endomorphs or bones. So that is yet to come.
I definately agree there. I'm also confident that NewTek will be improving them as they progress through 9.x. Right now NewTek's got a lot on their plate to change LightWave into a modern and next-gen application. CC subDs are only a small part of that, but I'm sure they'll get to it eventually.

Tyler007
02-09-2007, 12:24 PM
Well I hope they improve on it the concept is great or maybe a more easy way to work around the math of that is to have a mode where all the vertices have 3 points and just change the way the edges are displayed kind of like in Max and Maya. They have the look of more than 4 points but if you go in polygon mode (MAX) they really have all 3 point polys. I still like the old Dub-D in LightWave because it makes very clean objects. I have had problems in the new Sub-D with the knife tool and all the points are welded and a hole is still there but if I switch to the old Sub-D and it works. I only had problems with objects with this type of detail.

jasonwestmas
02-09-2007, 02:20 PM
I'd stick to four and five point patches when using CC. Since it is supposed to support Ngons I'd stick to trying out that feature rather than using three point polys next to eachother.

Surrealist.
02-10-2007, 02:23 AM
Well I hope they improve on it the concept is great or maybe a more easy way to work around the math of that is to have a mode where all the vertices have 3 points and just change the way the edges are displayed kind of like in Max and Maya. They have the look of more than 4 points but if you go in polygon mode (MAX) they really have all 3 point polys. I still like the old Dub-D in LightWave because it makes very clean objects. I have had problems in the new Sub-D with the knife tool and all the points are welded and a hole is still there but if I switch to the old Sub-D and it works. I only had problems with objects with this type of detail.

Looking at your model there. Its a nice model and you are doing a good job at achieving a complex geometry. If you rethink your polyflow you are going to have more sucess with subd. The more complex the shape the more you have to concentrate on simplicity.

Just on a cursory look I have found a few things that could be simplified, such as the large disc which looks as if it has been lathed.

I have attached a couple of very oversimplified examples of polyflow on primitive shapes. I have an object file full of these and many more simple primitives I worked out to help me understand polyflow and subd.

There are some great tutorials out there that I did as well.

If you look at those shapes in their simlicity you will see the polyflow you can use to achieve a disc with much less polygons. Oversimplified but that is the strengh of the concept - think simple.

I am achieving great results on a multitude of organic shapes - things, I'd love to show you but they are for a project so I can not disclose. But trust me, CC works, and it works quite well within rational guidelines of subd.