Can anyone shed a light on the Subdivision Options?

The Smooth Positions option is clear to me, but what about Subdivide UV’s and Smooth UV’s? In which cases are those needed?

I can’t find any additional information in the documentation.

Thanks in advance.

...and what is the options for production ready models ?

Addition to my original post;

Is it correct that these options only apply, when you use Mudbox for generating displacement maps which will be used on a subdivided mesh? In other words are not applicable when generating normal maps?

>>The Smooth Positions option is clear to me, but what about Subdivide UV’s and Smooth UV’s? In which cases are those needed? I can’t find any additional information in the documentation.

Yes, description of these options exists in the reference docs but is a bit light at present. This will get addressed in a future docs update.

Subdivide UVs: By default, UVs are not subdivided on a model when the model is subdivided. This saves memory since UVs add to the size of the file. When you first paint on a model on a subdivision level that has no UVs (at that level), but exist on a lower level), Mudbox will automatically subdivide the UVs up to that level for painting when you create the paint layer. Turning this option on will automatically subdivide UVs every time the model is subdivided....some users don’t want this in order to save memory.

Smooth UVs: By default, UVs are not smoothed whenever the UVs are subdivided. A user may want UVs smoothed if the model is eventually to be rendered as a subdivision surface in another application.

Hope this helps.

>>Is it correct that these options only apply, when you use Mudbox for generating displacement maps which will be used on a subdivided mesh? In other words are not applicable when generating normal maps?

Perhaps you can clarify your inquiry a bit...?

UVs are required for the following operations:
1. Painting on a model.
2. Applying texture maps on a material.
3. Extracting a texture map (Normal or Displacement)
...and likely I’ve forgotten something else.... ;-)

If the model is imported without any UVs you cannot create them in Mudbox.
You can only subdivide UVs or Recreate Level UVs if there are UVs on the base layer of the model you imported

You CAN import UVs onto the model afterwards from another 3D application using the .obj format however using File > Import UV.

UVs provide a correspondence between pixels in a bitmap image and vertices on the model...so whenever those two items need to correlate, UVs are required.

Check out the Mudbox Help: http://www.autodesk.com/mudbox-docsv2009
Check out the Import and Export section....UVs Overview, there are also cross references to other related areas.

jamieson,

First, thanks for your quick and elaborate replies.

And ha, I see the misunderstanding myself now. My second question;

>>Is it correct that these options only apply, when you use Mudbox for generating displacement maps which will be used on a subdivided mesh? In other words are not applicable when generating normal maps?

Refered to the options you have when you want to extract a Normal Map. Under Target Model you find the options to Smooth Target Model / Smooth Target UVs. (In my cases till now, if I check Smooth Target Model, the extracted Normal Map doesn’t fit the original UVs of the low resolution mesh, very obviously since they were “smoothed” internally when the Normal Map was extracted, correct me if I’m wrong here.) The low resolution meshes I’m using here will subsequently not be subdivided nor smoothed when used in production.

So in my case I guess these options are not applicable when generatng Normal Maps.

All in all, I do think however that these options and their explanation as well as the actual meaning of subdivision and/or smoothing are a bit confusing.

Thanks, yes I think I understand what you’re asking better now.

>>The low resolution meshes I’m using here will subsequently not be subdivided nor smoothed when used in production.

Correct....the model is not changed in Mudbox when these options are turned on. (see next paragraph) The subdividing/smoothing that occurs by these options in the Map Extraction window is only for extraction purposes in producing either a normal or displacement map...(that is, these options tell Mudbox to calculate the extracted maps “as if” the model was smoothed), but this stuff is not saved out. All that gets produced from this process is an image for either type of map. The models in the scene remain unchanged. I can understand how the option names can lead you to question this.

These options primarily exist so that if the user was to render the model as a subdivision surface in another application where the model might get further subdivided (Maya or Max).... (and the vertices are smoothed/moved in the process) that the extracted map will match the subdivision surface when its rendered. A games asset doesn’t get subdivided further at render time, so these options can/should be turned off so there is an exact match between the map and the mesh.

Hope that helps.

jamieson, thanks again, your explanation is very clear now.

What is confusing here is that “smooth” is used for subdividing and smoothing a mesh (including changing vertex positions and UV’s if needed) as well as that it can refer to smoothing vertex normals, which makes a mesh look smoothed. Hope you’re still with me here.. I’m using different software packages (Maya, Max, Modo) and the use of the term smooth is not always consistent.

Also refer to another related post here:
http://area.autodesk.com/for...nsmoothed-vertex-normals/

Yes, I can understand how the smoothing terminology can be confusing....it took me a while to understand it too....I probably don’t understand it yet as good as others....

In Mudbox’s case....

1. Subdivision of a surface divides the faces AND causes some reposition of the verts based on a particular algorithm it uses (Catmull Clark). You can actually turn this option off (Mesh > Add New Subdivision Level > Smooth Positions)...then only the subdivide occurs.
2. Smoothing of a surface (say with the smooth tool brush) averages the positions (height?) of the vertices in relation to each other in the areas you stroke with the tool.
3. In Maya (and other apps) a smooth operation is generally doing the smoothing as in “2” but does it globally on the entire mesh or whatever is selected when you invoke the tool.

Hope this helps.