Pointers on "smart" subsurf modelling


(Burre) #1

Hi there.

I understand this question must have been debated a lot but I decided to make a new thread based on two things:

  1. I read a thread, by a forum veteran, that wanted people to avoid “necromancing” of threads, and so I wont.

  2. New tools/code/scripts might have been added since, making some methods obsolete. (It is fine to take workflow examples that apply to the 2.4 alpha, but then please note that)

What I mainly hope for is to find a general approach on how to subsurf model correctly when mixing soft and hard edges. While doing so I wish to make sure that:

  • …it doesn’t increase complexity of the model if not necessary. For example I rather model with the modifier on than apply it to the mesh and repeat the process.

  • …it makes it as easy as possible to go back and re-edit it later. (i.e it should not “break” the model)

AFAIK there are only two ways to make hard edges on subsurfs: creases and added geometry. Creases keeps one from adding more complexity, but have the drawback of producing “normal problems” on very sharp edges. So if one wants very sharp edges the best bet imo is to go with added geometry. I usually use the loop-cut tool, but there are cases where it can be hard (i.e on areas that has bad quad-loops, wich sometimes is unavoidable).

So what do you “pro”-blendheads do to avoid problems on subsurf models? Please give examples.

Many thanks in advance!


(Clean3D) #2

I’m afraid I don’t really classify as a “pro” blenderhead (yet), but these are some things I usually try to do when subsurfing.

  1. Use quads as much as possible, but don’t be afraid to use tris if you have to.

  2. Join tris (alt-j).

  3. Try to use Edge Loop modelling. (Read section 4.2 of the wings3d manual)

  4. Think about how you’re model is going to be used. If you intend to animate it, your modelling is going to have to be much different than if it’s just static.

  5. Use added geometry. It gives you more control over how edges look.

  6. Get rid of all unneccesary vertices.

  7. When faced with an entire revamping of a model, say “Argh!” and begin the revamping. Don’t delay like I do. :wink:

  8. Try to get definite shapes that look like they’re really real instead of a really smooth CG thing. Use sharp edges and flat surfaces. One of the most irritating things to look at is a model that lookes like it’s a low-poly that’s been subsurfed without any additional editing.

  9. Render many different angles. Things will show up differently with full lighting than in Blender’s 3d view.

  10. Read the part on triangle stripping in this thread:
    http://forums.cgsociety.org/showthread.php?t=112189&page=1

  11. Try to keep most faces roughly the same size - Or at least don’t change the size throughout the mesh rapidly (You don’t want really small faces next to really big ones).

  12. Edit some while your mesh is subsurfed, and then turn subsurfing off and clean up the mesh. Avoid very sharp angles wildly twisted faces.

Just some of the stuff I do when subsurfing. I don’t run into many problems anymore, so I guess they can’t all be bad. I hope they aren’t.

Hope this helps! :slight_smile:


(Burre) #3

Thanks for the input. Though I already use most of these techniques it is nice to have it confirmed that I’m moving in the right direction.

When I said “pro” I didn’t refer to “elite”, but merely “seasoned” or “experienced”. I have for some time wanted to find a resonable way to use creases effectively since I’ve always felt adding geometry more of a “hack” than a logic approach, but I still keep coming back. The crease tool is actuallly quite ok when it comes to shaping meshes. It real weakness is that the mesh is often smoothed, and therefore the normal gets interpolated between the faces and thus messes with lighting. I think it might be possible to compensate for this to make it behave like a face-normal when edges are sharp, but it doesn’t seem to do that. I saw that someone was updating the tool (according to the wiki) but I’m not sure if the work is discontinued.

Another thing I’ve been thinking of lately. Some tools produce a lot of tris, more than necessary in fact. That is not the big problem though. The big problem is that it is cumbersome to clean up the mess. I would like a tool where, a bit like the “Rem doubles”-tool where one could automaticly merge tris who are connected (sharing an edge) and have a plane equation that is very close to each other (to form a “flat” quad). How close might be set by the user (similar to limit in “rem doubles”). It should also make sure to merge the tris wich share the biggest edge first (since this is most likely to be the hypotenuse), but that may be optional.

It would also be nice if the bridge- and “bevel center”-script became native tools since their uses are many and common.

I would also like to see more “helper-functions” to many modeling tools (like the ones found in Autocad). For instance, the possibility to lock manipulation along a plane normal. For example: pressing G for grab, pressing [some hotkey for this tool], selecting a face (it could automaticly jump into face select mode and then back to previous mode), a line is then drawn through this face’ normal (just like when constraining to an axis and when extruding) and manipulates it only alongside this axis. It might also use shift-click to constrain it to the plane (same as now with the axes, i.e shift-x selects the y/z-plane).

There are tons of other small nitpicks that really could enhance the current tools from good to “awesome”. The edge-slide function (currently in alpha) in one of those examples that have now been added to the tools. In relation to many features, these kinds of “helper-tools” are quite trivial, but adds a LOT to the workflow and the pace. It should be something to consider for future releases, imo. I’m not whining, and the current tools are great, I just meant that this is somewhat of an unexplored territory. hint hint :wink:


(tolobán) #4

The tri2quad.py script by cambo does a good job joining triangles, taking in account how coplanar the tringles are and how rectangular the resulting quad can be. It is slow for large meshes, but can save a lot of work, look for it here:

http://members.iinet.net.au/~cpbarton/ideasman/


(grafix) #5

The crease tool is a bit quirky, though. It tends to dissappear if you turned edges. Not sure about the alpha version, but in the current stable version 2.37a, if you have set up the edge weights, then turned an edge anywhere else in the object with the ctrl E,( rotate edges cw or ccw), the edge weights for the entire object disappears… just one thing to keep in mind.