OpenSubDiv and Triangles: Anyone see this?
wancow
Posts: 2,708
I was playing around with OpenSubDiv vertex weights and I just discovered something.
I creatred a cone, and wanted to see if the weight on the vert at the top of the cone displayed the same for each polygon... they are triangles...
Typical Catmul clark subdiv makes quads... but it LOOKS like these triangles were only divided in half... as in, not turned into quads, but into two triangles...
Am I seeing this correctly???
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Comments
Depends,
How are you viewing it?
Quad based meshes are split into triangles during rendering, even in the openGL renderer, so how you see a mesh can depend on your display setting.
I'm viewing it in OpenGL. I didn't know there was another way to see it. Quads subdivide into quads in OpenGL. X4 for every level of subdivision.
Hi wancow...
Did you create the cone using the Studio primatives?...
If so, the polygons on the top and bottom of the cone are made of triangles... if you add SubD to the cone, then the sub-division is made of quads... this is true with the old Catmull-Clark SubD in 4.5.1.56 and the new Catmark SubD in the new Beta .2.40... it's just really hard to see because it is at the very tip of the cone... it's easier to see on the bottom of the cone...
If you scale up the cone like 500% and zoom in you can just see the polys on the tip...
Catmull-Clark SubD will always divide base mesh triangles into sub-division quads, but the underlying triangles of the base mesh are still there as they make up the SubD cage...
That makes modelling with SubD cages very useful, because you can have triangles and ngons in the base cage, but the sub-division will be laid out in quads with very nice loops... so when modelling for DS or Poser, if your modeler supports it, you can create a very low-poly base cage that is full of tri's and ngons... have the SubD cage set to like 1 or 2 levels, and create your base form and topology for your model... then apply the cage as real geometry, thus creating a clean mesh of quads... you could then apply a new SubD cage to further refine your model...
nicci... :)
okay, you're right, I didn't zoom in enough... But yeah, I'm in the process of building a VERY low poly figure, and I'm wondering if I can use OSD in places like on the nose, etc...
Hi...
Well I would say yes and.... maybe...
It really depends on the way your modeler handles CC SubD and just as important, how the final version of OSD is implemented in DS...
For the modeling program, if it already has OSD incorporated (like Modo 701) then no problem... you build your model using OSD cages and then export using a compatible format to retain the vertex and edge crease weights or export the base cage to .obj and then set up the weights in DS...
Right now in the Beta, the OSD tools are very primitive and incomplete... selecting by vertex number and edge vertex pairings is not very efficient... and guessing at weight values makes if difficult also...
I hope that the final release version of the tools will have a better UI for the tools and viewport selection for the vertices and edges... maybe a slider for the weight values with real-time view of the changes... much like the way the tools behave when weight painting...
So, as I said... you can, but we'll have to kind of wait and see to what extent the OSD tools are implemented to really know how we'll be able to use them in our models...
nicci... :)
actually, as it stands, if you produce a very low poly model of say, a scifi fighter, the edge creasing becomes invaluable. You can make those edges nice and square and still have the benefit of subiv... so you still get a little roundness to it. I'll be playing with this quite a bit.
Agreed... :-)
OSD for things of the like is one of it great assets... were it becomes priceless is in figures that require both softness and hard or semi-hard edges... this is what has been lacking...
nicci... :)
Finally someone who understands why I'm so ecstatic about OSD!
Although modo uses "Pixar SubD", and open Sub Div is Pixar's, modo 701 doesn't formally support OSD - though the results should be very close.
I'm really hoping DAZ starts developing Hexagon again and that HEX 3 will support OSD.
Does the new Studio beta let you apply different levels of SubD on a per-surface basis? E.g., a wall and column part of the same object, you might want to leave the wall alone since it's flat, but add extra faces to the column to give it a smoother curve. In current released versions of Studio, "Convert to SubD" is an all-or-nothing affair for the entire object, regardless of how many surfaces it has in it.
That I'm not sure. I think the implementation of OSD in D|S is still in alpha stage.
If they plan on implementing that part of OSD, I do not think they have. I cannot find it if they have. I tested out on a surface with radical curves and flat areas, and it subdivided the same across all the polygons.
I do know that the subsivision default in D|S 4.5.2.40 is now OpenSubDiv.
One thing that I think is going to be hugely beneficial is that with OSD I can get meshes I have in D|S to ACT like meshes I have in Hexagon when Subdivided! So I can be reasonably sure that I can get what I see subdivided in Hex to look the same in D|S. It'll be tedious to fix edges and verts, but I'd rather have the control over than than not.
Hi...
I stand corrected... :) you're right, modo uses a licenced version of Pixar SubD which I would guess has all the bells and whistles... OSD is still Beta and is not fully featured as of yet...
As for different levels of SubD on the same model... no, not yet, but it is just an alpha.... but that would be great to have that feature implemented... ;-)
I think ( and this is just my opinion ) the current tool set for OSD in the beta is just to allow it to work... I couldn't imagine DAZ would leave it that way.... As I mentioned in my previous post, I would think the final tool set will be something similar to the weight tools, perhaps even in it's own pane and perhaps with the function to select surfaces for SubD levels...
Well... we can hope... ;-)
nicci... :)
I don't have access to any OSD tools. Could someone please show a screenshot of what the tool-set is supposed to look like, and where located.
I installed 32 bit version alongside my 64 bit 1.56 on Windows7, so 2.40 mirrors my main install. There are no issues (other than no access to the tools), and I have all the new subdivision modifiers.
I have checked in the custom parameters module, but I could not locate anything there to add to the UI.
And, wancow, I have found the new Sub-D levels to be dependent on loaded mesh. First low poly mesh I loaded gave me the four levels, but subsequent mesh loading yielded only 2 or 3 max levels depending on original mesh density.
it's in the Tools Tab when you select the Polygon Selection Tool. I've seen as high as seven levels of subdivision available.
Thank you, wancow.
I did not see anything regarding they bundled it with the Polygon Group Editor. Cool, they added another tab page. I was looking for it's own tool "button" in the Tools toolbar (or a way to add one).
Seven, eh? Was it a single plane? I couldn't imagine anything needing that much smoothing applied.
And here I thought four was impressive. Though, I will probably limit my view-port to level one, it is nice to see what attribute we could set the renderer to.
Thanks again, wancow...
One thing I'm thinking is that the subdiv levels need to be tweaked so that a value of 1-4 crease less... of course, those values might be set in the code, and unalterable...