- Smooth Positions
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When on (default), applies a global smoothing operation to vertices on the model each time it is subdivided (based on a Catmull-Clark algorithm).
- Subdivide UVs
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When on, subdivides the model’s UV texture coordinates for each subdivision operation. When off (default), subdivision levels higher than Level 0 do not have UVs applied until they are required. For example, UVs are applied to a higher level when you paint on the model. The default is off.
- Smooth UVs
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When on, applies global smoothing to the model’s UV texture coordinates each time it is subdivided. Smoothing UVs is useful if the model will be rendered as a subdivision surface model in another application that supports a similar UV smoothing algorithm as Mudbox. Off by default.
Note: If you plan to use your subdivided mesh as a source or target for a vector displacement map, it's recommended that you turn this on to achieve optimal results. - Boundary Rule
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Lets you set how you want creasing applied to boundary edges and vertices as you subdivide the mesh. This option is based on the Boundary Rule setting found in Maya. Select from the following rules:
- Crease Nothing
- Apply no creasing to boundary edges and vertices. (Corresponds to the Boundary Rule: Legacy option in Maya.)
- Crease Vertices and Edges
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(Default.) Apply full creasing to all boundary edges and all vertices that have only two incident edges before being converted to a smooth mesh. (Corresponds to the Boundary Rule: Crease All option in Maya.)
- Crease Edges
- Apply full creasing to edges only. (Corresponds to the same option in Maya.)
- Preserve Borders
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When on, Mudbox preserves border edges when you subdivide the mesh. (Border edges are not smoothed.)
- Preserve UV Borders
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When subdividing a mesh, Mudbox also subdivides the UVs of that mesh. This setting lets you control whether Mudbox preserves the borders of UV areas during subdivision. Preserving UV borders can be important depending on the renderer you use to render your maps.
When off, smoothing only occurs for the interior UVs in a UV shell, leaving the UV shell border edges unsmoothed.
- Preserve Hard Edges
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Only available when the active mesh has hard edge data (for example, smoothing groups imported from Softimage or hard edge data from Maya). When on, Mudbox preserves hard normals so they also appear when you subdivide the mesh.
- Crease Hard Edges
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Available only when Preserve Hard Edges is on. When on, Mudbox handles hard edges as infinite creasing edges during subdivision and creates a continuous crease, similar to hard edges with the TurboSmooth modifier in 3ds Max. This means edges are only smoothed along the edge direction, but not smoothed along the direction across the edges. Normals along the edges are changed smoothly, but normals on the left side of the edge change dramatically to normals on the right side. (The effect is to round over corners and edges.)
When off, the hard edges are fixed (meaning they are subdivided in a linear fashion and not smoothed at all, like in Maya). For new vertices inserted during subdivision, Mudbox uses linear interpolation from the original hard edges to determine the angles of new faces at corners and edges.
The following images illustrate the difference between a mesh subdivided twice with Crease Hard Edges on, and off.
- Preserve Creasing
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When on, edges with creases are preserved during subdivision and only smoothed in one direction, along the edges. When off, subdivision ignores the creasing.